CA1194613A - Microelectronic shadow masking process for reducing punchthrough - Google Patents
Microelectronic shadow masking process for reducing punchthroughInfo
- Publication number
- CA1194613A CA1194613A CA000407811A CA407811A CA1194613A CA 1194613 A CA1194613 A CA 1194613A CA 000407811 A CA000407811 A CA 000407811A CA 407811 A CA407811 A CA 407811A CA 1194613 A CA1194613 A CA 1194613A
- Authority
- CA
- Canada
- Prior art keywords
- layer
- gate
- regions
- masking
- substrate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000000034 method Methods 0.000 title claims abstract description 63
- 230000008569 process Effects 0.000 title claims abstract description 48
- 230000000873 masking effect Effects 0.000 title claims abstract description 42
- 238000004377 microelectronic Methods 0.000 title description 5
- 239000000758 substrate Substances 0.000 claims abstract description 25
- 150000002500 ions Chemical class 0.000 claims abstract description 24
- 238000005530 etching Methods 0.000 claims abstract description 20
- 238000009826 distribution Methods 0.000 claims abstract description 13
- 239000002019 doping agent Substances 0.000 claims abstract description 7
- 239000004065 semiconductor Substances 0.000 claims description 23
- 229910021420 polycrystalline silicon Inorganic materials 0.000 claims description 21
- 229920002120 photoresistant polymer Polymers 0.000 claims description 20
- 239000004020 conductor Substances 0.000 claims description 18
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 17
- 229920005591 polysilicon Polymers 0.000 claims description 17
- 239000010703 silicon Substances 0.000 claims description 16
- 229910052710 silicon Inorganic materials 0.000 claims description 15
- 239000012535 impurity Substances 0.000 claims description 11
- 238000010894 electron beam technology Methods 0.000 claims description 10
- 238000005468 ion implantation Methods 0.000 claims description 8
- 239000000463 material Substances 0.000 claims description 7
- 238000002513 implantation Methods 0.000 claims description 6
- 238000012545 processing Methods 0.000 claims description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 5
- 230000005669 field effect Effects 0.000 claims description 5
- 239000003870 refractory metal Substances 0.000 claims description 5
- 229910021332 silicide Inorganic materials 0.000 claims description 5
- FVBUAEGBCNSCDD-UHFFFAOYSA-N silicide(4-) Chemical compound [Si-4] FVBUAEGBCNSCDD-UHFFFAOYSA-N 0.000 claims description 4
- 229910052814 silicon oxide Inorganic materials 0.000 claims description 4
- 239000002131 composite material Substances 0.000 claims description 3
- 229910052715 tantalum Inorganic materials 0.000 claims description 2
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 claims description 2
- 229910021341 titanium silicide Inorganic materials 0.000 claims description 2
- WQJQOUPTWCFRMM-UHFFFAOYSA-N tungsten disilicide Chemical compound [Si]#[W]#[Si] WQJQOUPTWCFRMM-UHFFFAOYSA-N 0.000 claims description 2
- 229910021342 tungsten silicide Inorganic materials 0.000 claims description 2
- 229910052594 sapphire Inorganic materials 0.000 description 9
- 239000010980 sapphire Substances 0.000 description 9
- 238000004519 manufacturing process Methods 0.000 description 5
- 229910008062 Si-SiO2 Inorganic materials 0.000 description 4
- 229910006403 Si—SiO2 Inorganic materials 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 238000001020 plasma etching Methods 0.000 description 3
- 241000894007 species Species 0.000 description 3
- 238000004590 computer program Methods 0.000 description 2
- 239000007943 implant Substances 0.000 description 2
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 2
- 238000000992 sputter etching Methods 0.000 description 2
- 229910052581 Si3N4 Inorganic materials 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 238000004380 ashing Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000001312 dry etching Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- BHEPBYXIRTUNPN-UHFFFAOYSA-N hydridophosphorus(.) (triplet) Chemical compound [PH] BHEPBYXIRTUNPN-UHFFFAOYSA-N 0.000 description 1
- 238000010884 ion-beam technique Methods 0.000 description 1
- 238000001459 lithography Methods 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/66007—Multistep manufacturing processes
- H01L29/66075—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials
- H01L29/66227—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials the devices being controllable only by the electric current supplied or the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched, e.g. three-terminal devices
- H01L29/66409—Unipolar field-effect transistors
- H01L29/66477—Unipolar field-effect transistors with an insulated gate, i.e. MISFET
- H01L29/66742—Thin film unipolar transistors
- H01L29/66772—Monocristalline silicon transistors on insulating substrates, e.g. quartz substrates
- H01L29/6678—Monocristalline silicon transistors on insulating substrates, e.g. quartz substrates on sapphire substrates, e.g. SOS transistors
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/027—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34
- H01L21/0271—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising organic layers
- H01L21/0273—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising organic layers characterised by the treatment of photoresist layers
- H01L21/0277—Electrolithographic processes
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- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/26—Bombardment with radiation
- H01L21/263—Bombardment with radiation with high-energy radiation
- H01L21/265—Bombardment with radiation with high-energy radiation producing ion implantation
- H01L21/266—Bombardment with radiation with high-energy radiation producing ion implantation using masks
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- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/40—Electrodes ; Multistep manufacturing processes therefor
- H01L29/41—Electrodes ; Multistep manufacturing processes therefor characterised by their shape, relative sizes or dispositions
- H01L29/423—Electrodes ; Multistep manufacturing processes therefor characterised by their shape, relative sizes or dispositions not carrying the current to be rectified, amplified or switched
- H01L29/42312—Gate electrodes for field effect devices
- H01L29/42316—Gate electrodes for field effect devices for field-effect transistors
- H01L29/4232—Gate electrodes for field effect devices for field-effect transistors with insulated gate
- H01L29/42384—Gate electrodes for field effect devices for field-effect transistors with insulated gate for thin film field effect transistors, e.g. characterised by the thickness or the shape of the insulator or the dimensions, the shape or the lay-out of the conductor
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- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/40—Electrodes ; Multistep manufacturing processes therefor
- H01L29/43—Electrodes ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
- H01L29/49—Metal-insulator-semiconductor electrodes, e.g. gates of MOSFET
- H01L29/4908—Metal-insulator-semiconductor electrodes, e.g. gates of MOSFET for thin film semiconductor, e.g. gate of TFT
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- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/66007—Multistep manufacturing processes
- H01L29/66075—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials
- H01L29/66227—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials the devices being controllable only by the electric current supplied or the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched, e.g. three-terminal devices
- H01L29/66409—Unipolar field-effect transistors
- H01L29/66477—Unipolar field-effect transistors with an insulated gate, i.e. MISFET
- H01L29/66568—Lateral single gate silicon transistors
- H01L29/66575—Lateral single gate silicon transistors where the source and drain or source and drain extensions are self-aligned to the sides of the gate
- H01L29/6659—Lateral single gate silicon transistors where the source and drain or source and drain extensions are self-aligned to the sides of the gate with both lightly doped source and drain extensions and source and drain self-aligned to the sides of the gate, e.g. lightly doped drain [LDD] MOSFET, double diffused drain [DDD] MOSFET
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- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
- H01L29/76—Unipolar devices, e.g. field effect transistors
- H01L29/772—Field effect transistors
- H01L29/78—Field effect transistors with field effect produced by an insulated gate
- H01L29/786—Thin film transistors, i.e. transistors with a channel being at least partly a thin film
- H01L29/78606—Thin film transistors, i.e. transistors with a channel being at least partly a thin film with supplementary region or layer in the thin film or in the insulated bulk substrate supporting it for controlling or increasing the safety of the device
- H01L29/78618—Thin film transistors, i.e. transistors with a channel being at least partly a thin film with supplementary region or layer in the thin film or in the insulated bulk substrate supporting it for controlling or increasing the safety of the device characterised by the drain or the source properties, e.g. the doping structure, the composition, the sectional shape or the contact structure
- H01L29/78621—Thin film transistors, i.e. transistors with a channel being at least partly a thin film with supplementary region or layer in the thin film or in the insulated bulk substrate supporting it for controlling or increasing the safety of the device characterised by the drain or the source properties, e.g. the doping structure, the composition, the sectional shape or the contact structure with LDD structure or an extension or an offset region or characterised by the doping profile
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- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
- H01L29/76—Unipolar devices, e.g. field effect transistors
- H01L29/772—Field effect transistors
- H01L29/78—Field effect transistors with field effect produced by an insulated gate
- H01L29/786—Thin film transistors, i.e. transistors with a channel being at least partly a thin film
- H01L29/78606—Thin film transistors, i.e. transistors with a channel being at least partly a thin film with supplementary region or layer in the thin film or in the insulated bulk substrate supporting it for controlling or increasing the safety of the device
- H01L29/78618—Thin film transistors, i.e. transistors with a channel being at least partly a thin film with supplementary region or layer in the thin film or in the insulated bulk substrate supporting it for controlling or increasing the safety of the device characterised by the drain or the source properties, e.g. the doping structure, the composition, the sectional shape or the contact structure
- H01L29/78621—Thin film transistors, i.e. transistors with a channel being at least partly a thin film with supplementary region or layer in the thin film or in the insulated bulk substrate supporting it for controlling or increasing the safety of the device characterised by the drain or the source properties, e.g. the doping structure, the composition, the sectional shape or the contact structure with LDD structure or an extension or an offset region or characterised by the doping profile
- H01L29/78627—Thin film transistors, i.e. transistors with a channel being at least partly a thin film with supplementary region or layer in the thin film or in the insulated bulk substrate supporting it for controlling or increasing the safety of the device characterised by the drain or the source properties, e.g. the doping structure, the composition, the sectional shape or the contact structure with LDD structure or an extension or an offset region or characterised by the doping profile with a significant overlap between the lightly doped drain and the gate electrode, e.g. GOLDD
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- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
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- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
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- H01L29/76—Unipolar devices, e.g. field effect transistors
- H01L29/772—Field effect transistors
- H01L29/78—Field effect transistors with field effect produced by an insulated gate
- H01L29/786—Thin film transistors, i.e. transistors with a channel being at least partly a thin film
- H01L29/78606—Thin film transistors, i.e. transistors with a channel being at least partly a thin film with supplementary region or layer in the thin film or in the insulated bulk substrate supporting it for controlling or increasing the safety of the device
- H01L29/78618—Thin film transistors, i.e. transistors with a channel being at least partly a thin film with supplementary region or layer in the thin film or in the insulated bulk substrate supporting it for controlling or increasing the safety of the device characterised by the drain or the source properties, e.g. the doping structure, the composition, the sectional shape or the contact structure
- H01L29/78621—Thin film transistors, i.e. transistors with a channel being at least partly a thin film with supplementary region or layer in the thin film or in the insulated bulk substrate supporting it for controlling or increasing the safety of the device characterised by the drain or the source properties, e.g. the doping structure, the composition, the sectional shape or the contact structure with LDD structure or an extension or an offset region or characterised by the doping profile
- H01L2029/7863—Thin film transistors, i.e. transistors with a channel being at least partly a thin film with supplementary region or layer in the thin film or in the insulated bulk substrate supporting it for controlling or increasing the safety of the device characterised by the drain or the source properties, e.g. the doping structure, the composition, the sectional shape or the contact structure with LDD structure or an extension or an offset region or characterised by the doping profile with an LDD consisting of more than one lightly doped zone or having a non-homogeneous dopant distribution, e.g. graded LDD
Abstract
Abstract A process for forming a doped region in a substrate which is in alignment with a circuit member by forming a masking member on a layer, the masking member defining the outline on the circuit member;
and etching the layer employing the masking member as a mask to define the circuit member, the etching continuing such that the circuit member includes sloping side faces. Subsequently, a dopant species is implanted into the substrate so as to form the doped region, the dosage and energy of ions implanted being selected such that ions are partially blocked by the portion of the circuit member beneath the sloping side faces thereby providing a more lightly doped and more shallow distribution of implanted species region than in other regions.
and etching the layer employing the masking member as a mask to define the circuit member, the etching continuing such that the circuit member includes sloping side faces. Subsequently, a dopant species is implanted into the substrate so as to form the doped region, the dosage and energy of ions implanted being selected such that ions are partially blocked by the portion of the circuit member beneath the sloping side faces thereby providing a more lightly doped and more shallow distribution of implanted species region than in other regions.
Description
MICROELECTRONIC SHADOW MASKING
PROCESS FOR REDUCING PUNCHTHROUGH
BACK~ROUND OF THE INVENTION
Field of the Invention The invention relates to shadow masking processes in micro-electronic fabrication, particularly those employed in silison-on-sapphire (SOS) processes.
Description of the Prior Art The fabrication of integrated circuits such as metal oxide semiconductor (MOS) circuits employing a mask and photolithographic techniques is well known in the art. One of these methods, known as the self-aligned gate procedure, utilizes a gate conductor pattern to shield the channel region of ~he device from N~ or P~ ion implantation during formation of the source and drains of the device. In such processes, the entire dimension of the gate, L, shields the channel region which has an area L by W (wherein W is within the channel region~
from the N+ or P+ ion implantation due to the thickness of the gate conductor. The source and drain regions of the device fabricated accord-ing to such a self-aligned gate process are not appreciably overlapped by the gate and therefore the Miller capacitance of the device is minimized.
Although such a procedure is adequate for many standard commercial products, when the channel of the device is reduced to sub-micrometer dimensions, such as VLSI or highly integrated devices, the depletion layers in the source and drain regions overlap to a cer~ain extent depending upon the doping concentration distribution of the channel region of the device. It should be noted that in the enhancement mode, depletion mode, or deep depletion mode of operation of the device~ the channel region will be bounded by a vertical N~ and P~ region for ~he source and drain down to at least a distance of 0.25 micrometers from the silicon/silicon dioxide interface and usually through the entire Si film to the sapphire. This bound is due to the vertical slope of the etches of the gate conductor. Immediately below the channel region~ the depletion layers overlap more and punchthrough is enhanced. Punchthrough i5 symptomized by a drain-souxce voltage dependence of the subthreshold currentr It is also known as a short channel effect.
One approach to a channel making process for forming the source and drain regions as a MOS device is shown in U~S. Patent No~ 4,198,250, which utilizes a gate masking member which is etched and the gate oxide beneath the gate undercut to form overhangs. When a substrate is subjected to ion implantation with such a mask, a much shallower concentration of impuri~ies is implanted in the substrate beneath the overhangs than in the substrate region not protected by the masking member. Such a process provides self alignment for the gate and the source and drain regions will be overlapped by thP gate more than with the plain self-aligned gate process. The Miller capacitance will be increased slightly compared to the usual S.A.G. (Self-Aligned Gates) process, but, the likelihood for punchthrough is reduced~
The disadvantage of the process described in the above noted patent is that the amount of undercut for sub-micrometer gate dimensions is uncontrollable. The prior art describes a process for 2-4 ~m gate lengths where the undercut is typically 0.25 to 0.5 ~m on each sideO However, it is obvious that any undercut of a 0.5 ~m gate length will be too significantl e.g., only 300 Angstroms on a side undercut is 12% and is not uniform from wafer to wafer and on an individual wafer because of the isotropic etches required by the prior art.
~ ntion In accordance with an aspect of the invention there is provided a process for controlling the impurity profile distribution in a bady of semiconductor material which includes a conductive layer, comprising the steps of defining a masking member on a laterally extending major surface of said body in a predetermined pattern; etching said surface and said body through said conductive layer using said masking member as a mask so as to form a truncated, pyramidal shaped gate element having sides which - ~a -slope to form taperec? gate edges and ion implanting active regions of said semiconductor circuit using said gate element as a mask so as to form active regions having lighter and shallower degenerately doped p~ortions under said tapered gate edges, a channel region being defined under said gate element between said active regions, the length of said channel region extending between said active regions under said gate element, the length of said channel region between said degenerately doped portions being less than the length of said channel region beneath said degenerately doped portions.
Briefly and in general terms, the present invention describes a process for forming a doped region in a substrate which is in alignment with a circuit memberO
More particularly, the invention includes the steps~of forming a masking member or. a upper layer portion of the substrate, the masking member defining the outline of the circuit member; and etching the layer employing the masking member as a mask to define the circuit member, the etching GO continuiny such that the circuit member includes sloping side faces. ~n impurity is then ion implanted into the substrate so as to form the doped region, the dosage and energy of ions implanted being selected such that ions are partially blocked by the portions of the circuit member beneath the sloping side faces, thereby providing a more light1y doped and more shallow distribution of implanted species in the substrate region under the sloping side faces which is an extension of ~he doped region, than in the doped region.
The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages ~hereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
Brief Description of the Drawings Figure 1 is a cross-sectional view of a silicon-on-sapphire structure according to the prior art;
Figure 2 is a cross-sectional view of a silicon-on-sapphire structure employing the truncated pyramidal gate element according to the present invention~
Figures 3a through 3e are cross-sectional views of a silicon-on-sapphire structure illustrating the sequence of steps for forming the doped source and drain regions in the said layer according to the present inventicn.
Uescription of the Preferred Embodiment Figure 1 is a cross-sectional view of a silicon-on-sapphire structure using a self~aligned gate (S.A.G.) process. The Figure shows the sapphire (A1203~ substrate, a silicon layer thereover with heavily implanted regions (P++ and N~+) shown cross-hatched~ and the shape and position of the ga~e condwctor. The gate oxide is not shown for simplicity, although the gate oxide thickness tgateoX is represented in the Figure, as well as the thickness of the gate t~.
The fabrication process according to the present invention is based upcn an analysis of the submicrometer gate length structure of the depletion layers which is predicted, or analyzed, by such device per-formance computer programs as GEMINI (GEMINI Program, Stanford University E7ec~ronics Laboratory) and others which calculate the e1ectric field distribution in two dimensions in the channel and are capable of using fabrication process parameter data from computer programs such as SUPREM (SUPREM Program, Stanford University Electronics Labroatory~.
If the length of the channel region is somehow increased in the channel region approximately 0.25~m below the Si-SiO2 interface (where the total SOS film thickness is ~ 0.5~m), the conditions for punchthrough are reduced and the short channel behavior of the device can be eliminated under proper design constraints with respect to the channel dopant concentration profiles.
Twrning next to Figure 2, there is shown a cross-sectional view of a CMOS/SOS device fabricated according to the technique of the present invention. It is noted that the gate elements in both the N-MOS and P-MOS transistors are depicted in the cross-sectional view are in the shape of a trapezoidO In three dimensions, the shape of the gate element would be a truncated pyramid. It is noted from Figure 2 that the sides of the pyramid are slopped away from the normal or perpendicular direction to the surface by an angle of ~
where ~ is greater than 30. The truncated portion of the pyramid has a -top major surface with a length equal to "L", approximately 0.5 to 0.75 micronsO The ~hickness of the gate -tg is typically between 3000 and 4000 Angstroms. The length of the base of the pyramid is L~, which is L + 2tg Tan ~. The typical experimental data shows L =
0.7~, (with tg = 3050 Angstroms). The distance between the bottom surface of the gate element and the upper major surface of the silicon 3a structure~ which is equivalent to the thickness of the gate oxide is toX, which is approximately 100 to 350 Angstroms.
The fabrication process according to the present invention focuses upon the masking property of a circuit member, such as the gate conductor, as a function of its thickness with respect to the N+ and P~ ion implants3 and also upon the slope o~ the gate conductor edges deviating from the vertical. Although if the thickness, t, of the gate conductor at any point on the dimension of the gate conductor is less than that required ~o shield~ or mask, the channel region ~rom the N+
or P+ S.A.G. implants, tg, the dopant ions will penetrate into the silicon immediately beneath the Si-SiO2 interface to an extent depending upon the extent that the gate conductor thickness is less than tg~ A
gate conductor with edges that deviate from the vertical by some angle, ~, will therefore have a degenera~ely doped S and D region tha~ will extend beneath the maximum dimension, Lm~ of the gate with a depth distribution that will depend on ~ as shown in the cross-sectional view of the device according to the present invention in Figure 2.
The etch procedure requires a definitely anisotropic characteristic such that the sloped resist edge profile of the gate pattern is faith-fully reproduced in the ga~e conductor. There is no masking member of the gate conductor other than the resist hence there is one less oxidation and etch step than the prior art. The gate oxide (100-350 Angstroms) is not etched. It is most important to point out from this fiyure that the channel dimension at about 0.25~m below the Si-SiO2 interface where punchthrough of the S and D depletion regions was formerly a problem~ is now increased to a dimension, L~ > L. Therefore, the principal source of the short channel behavior of submicrometer MOSFET devices can be eliminated or at least greatly reduced in the structure formed by the process according to the present invention.
6~3 Turning next to the silicon structure itself, it is noted ~hat the source and drain regions are de~ermined by ion implanting through the gate oxide layer with the region under the gate pyramid being masked from the implant by the gate material of thickness, tg. The areas ion implanted are indicated by the cross hatched regions in Figure 2 to indicate that the amount of implantation or concentration of the dopant species is controlled so that some implantation occurs through the thin tapered edges of the gate element to form a lighter and shallower degenerately doped region directly under the tapered edges of the gate adjacent to the top major surface of the silicon semiconductor. The Figure indicates that this shallower degenerately doped region extends into the semiconductor body a distance of approximately 0.25 microns. Most of the ion implantation is implanted into the semiconductor body in the regions not protected by the masking member formed by the gate element. Directly underneath the center portion of the gate element there is effectively no ion implantation in~o the semiconductor body.
The GEMIMI Program can be used to predict the device behavior with respect to the short channel effect and is based similar to the ",3e71 Criterion." (J. R. Brews et al, IEDM Washington9 D.C., December 1979). If L~ or L is large enough such ~ha~ the subthreshold MOSFET
current will have a negligible dependence on the drain supply voltage, VD, the criterion for L or L~ being large enough depends upon the channel dopant conoentration and its pro~ile with respect to depth into the silicon frum the Si-SiO2 interface.
A sloped gate edge connector can readily be fabricated by the technique according to the present invention. An image reversal resist techniquc using electron beam exposure of a positive photo-resist followed by an optical UV flood exposure results in the positiYe photoresist behaving as a negative resist. (W. G. Oldham, E. Heike3 IEEE Trans. EDL-l (10~, 217, 1980). The resist edge profiles using this method are sloped with some angle, ~, from the vertical. If a dry etching technique (Fineline Lithography, Roger Newman ed., North Holland Publishing Co., Amsterdam, 1980 (Chap. 4., R. L. Maddox, M. R. Splinter))9 such as ion milling, reactive ion etching, parallel plate plasma etching, or reactive ion beam etching is used, an etched gate conductor profile with slope of angle, ~, can be faithfully reproduced from the resist profile.
In additiong the characteristic of sloped gate conductor edge profiles allows for a much relaxed step coverage condition in consideration of conductor layers deposited on top of the gate con-ductor pattern which criss-cross and still maintain continuity such as is required for VLSI.
One possible drawback regarding the present configuration is the increased Miller capacitance caused by the gate electrode overlapping the sloped gate edges. This overlap will be equal to X - tg tan ~.
With an angle on the order of 45, the current tg is about 0.3~m.
Therefore, a Miller capacitance of about 30% of the channel gate input capacitance would be the result. However, for submicrometer devices, the gate input capacitance is no longer the dominan~ factor compared to the interconnect capacitance and, hence, the speed of the device would not be nearly as affected as if the situation were directly scaled up to a 4~m gate length~for example. Note also that can be adjusted by the Elec~ron Beam Lithographic, EBL, or other resist processing variables with respect to the image reversal technique ~W. G. 01dham, E. Heinke, IEEE Trans. EDL-l ~10), 217, 1980) such that the overlap capacitance is less than 30%. Also, tg can be adjusted for a reduction. However, reducing the Miller capacitance will reduce L~ and a compromise must be made.
8~ ~46 Turning next to Figures 3a through 3e, there is shown the sequence of steps for forming the gate elements and the implanted source and drain regions according to the present invention.
Turniny first ~o Figure 3a, there is shown a composite of a silicon-on-sapphire structure which may be used for ion implanting according to the present invention. The silicon layer sn the sapphire substrate typically has a thickness between 4500 and 6000 Angstroms. The structure includes a gate oxide 1ayer on the top major surface of the silicon layer, followed by a -polycrystalline silicon (polysilicon~
layer over the oxide layer. The polysilicon layer is typically doped with phosphorous so that it is N+ conductivity and has a ~hickness between 800 and 1200 Angstroms. A molysilicide layer is applied over the P~ or N+ polysilicon layer, and a photoresist layer applied over the molysilicide layer. The use ~f any suitable refractory metal silicide (e.gO tantalum silicide, tungsten silicide or titanium silicide) is also within the scope of the present invention. The use of a poly-silicon-molysilicide layer is used in the pre~erred embodiment because of the greater conductivity provided by such a structure and its suitability for ultra large scale integrated devices. Other conductive layers can be used as well. According to the techniques of the present invention, the photoresist layer is a posi~ive photoresist layer.
Turnin~ next to Fi~ure 3b, there is shown the step in which the photoresist layer is selectively exposed to an electron beam in a predetermined pattern. The layer of photoresist is exposed where the electron beam passes and this photoresist layer portion is to remain after further processing.
The e7ectron beam is directed to the resist substantially normal to the surface of the resist layer. As it penetrates into the thickness of the layer, the electron ~eam scatters, and diverges from the surface.
The net affect of the scattering of the electrons in the resist layer is the exposure of the resist in a cross-section representing a trapezoid such as that shown in Figure 3b. Since the area exposed by the electron beam is typically that of a gate element, or other channel structure in a self-aligned MOS-MIS-MES device, the actual geometric structure exposed in the resist layer is that of a truncated pyramid.
The use of an electron beam for exposure of a positive resist is also described in the article W. G. Oldham, E. Heinke, IEEE Trans. EDL-1 (10), 217, 19~0.
Following exposure to the electron beam, the entire photoresist layer is f100ded with ultraviolet light. The ultraviolet light reacts differently with the portions of the resist exposed by the electron beam ~han the portions which have not been exposed. The net effect is that after the layer of photoresist is etched, the portions which have been exposed to the electron beam remain, such as shown in Figure 3c. The truncated pyramidal resist structure is then used as a mask for removing portions of the conductive layer which do not lie under the mask. The removal of -these portions of the conductor layer is achieved by a standard etching process such as reactive ion etching or ion milling.
The etching process leaves truncated pyramidal elements consisting nf a top layer of resist, followed by a lower conductive layer or layers. Such truncated pyramidal structures lie on the silicon oxide surface of the body as is shown in Figure 3d.
The next process step is to remove the remaining resist la~yer from the top of the pyramid. This is performed by the process of ~ plasma ashing.
The structure which remains is shown in Figure 3e which consists of a truncated pyramidal gate type element which overlies the silicon semiconductor body. Such a structure is then used as a mask for ion implanting the source and drain regions of the sem;conductor body in a self-ali~ned manner as is known in the techniques according to the art. The impurity profiled distribution in the source and drain regions and in the channel after ion implantation is substantially as shown in Figure 3e~ The net effect is that the distance between the source and drain regions are closest at the surface of the semiconductor body and spaced ~urther apart as the distance from the surface increases.
It is noted th~t some implantation occurs in the substrate region below the sloping side faces of the ga~e-type circuit element.
Such implantation results in the formation of a more lightly doped source and drain regions benea~h such side faces, while more heavily doped source and drain regions are provided in the silicon regions unprotected by the masking member. The doses and energy of the ions implanted are so selected such that the ions are partially blocked by ~he portion of the gate structure beneath the sloping side faces, so as to provide a more shallow distribution of the implanted s~ecies in the region directly underneath the sloping side faces than in nther regions.
The result of the formation of the gate element according to the present invention is a self-aligned process in which the distance between the source and the drain regions in the depth of the semi-conductor body (i.e.5 semiconductor regions deeper than 0.25~ from the top major surface) are relatively spaced apart a greater distance than at the surface, thus minimizing the problem of punchthrough.
While the invention has been illustrated and described as embodied in a microelectronic shadow maskiny process for reducing punchthrough, it is not intended to be limited to the details shown, since various modifications and structural changes ~ay be made without departing in any way from the spirit of the present invention.
It will be obvious to those skilled in the art that the semiconductor device according to the present invention can be implemented with various semiconduc~or technologies and different combinations of known process steps, and that the preferred embodiments illustrated here are merely exemplary. The depth of penetration of the various zones and regions and in particular the configuration and distance between the active zones of the transistor devices, as well as the concentrations of dopant species, and/or their concentration profiles, can be chosen depending upon the desired properties. These and other variations can be further elaborated by those skilled in the art without departing from the scope of the present invention.
The present lnvention is moreover not restricted to the particular embodiments of a microelectronic shadow masking process for reducing punchthrough described. For example, it may be pointed out that semi-conduc~or materials other than silicon, for example, A~ BV compounds may be used. Furthermore7 the conductivity types in the embodiment may be interchanged and corresponding to such change, the voltage level and the static or dynamic nature of the signals applied to the various terminals and gates of the device, as well as the voltage sources~ may be suitably selected as desired for a particular application. Other types of semiconductor circuits including bipolar junction field effect transistor, MNOS ~metal electrode-silicon nitride, silicon oxide-semiconductor), MAOS (metal aluminum oxide, silicon oxide, semiconductor), MAS (metal, aluminum oxide, semiconductor), flcating gate FETs, and AMOS FETs (avalanche MOS FETs), may be used as well.
Without further ana1ysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art~ fairly constitutes essential characteristics of the generic or specific aspects of this invention, and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.
What is claimed is:
PROCESS FOR REDUCING PUNCHTHROUGH
BACK~ROUND OF THE INVENTION
Field of the Invention The invention relates to shadow masking processes in micro-electronic fabrication, particularly those employed in silison-on-sapphire (SOS) processes.
Description of the Prior Art The fabrication of integrated circuits such as metal oxide semiconductor (MOS) circuits employing a mask and photolithographic techniques is well known in the art. One of these methods, known as the self-aligned gate procedure, utilizes a gate conductor pattern to shield the channel region of ~he device from N~ or P~ ion implantation during formation of the source and drains of the device. In such processes, the entire dimension of the gate, L, shields the channel region which has an area L by W (wherein W is within the channel region~
from the N+ or P+ ion implantation due to the thickness of the gate conductor. The source and drain regions of the device fabricated accord-ing to such a self-aligned gate process are not appreciably overlapped by the gate and therefore the Miller capacitance of the device is minimized.
Although such a procedure is adequate for many standard commercial products, when the channel of the device is reduced to sub-micrometer dimensions, such as VLSI or highly integrated devices, the depletion layers in the source and drain regions overlap to a cer~ain extent depending upon the doping concentration distribution of the channel region of the device. It should be noted that in the enhancement mode, depletion mode, or deep depletion mode of operation of the device~ the channel region will be bounded by a vertical N~ and P~ region for ~he source and drain down to at least a distance of 0.25 micrometers from the silicon/silicon dioxide interface and usually through the entire Si film to the sapphire. This bound is due to the vertical slope of the etches of the gate conductor. Immediately below the channel region~ the depletion layers overlap more and punchthrough is enhanced. Punchthrough i5 symptomized by a drain-souxce voltage dependence of the subthreshold currentr It is also known as a short channel effect.
One approach to a channel making process for forming the source and drain regions as a MOS device is shown in U~S. Patent No~ 4,198,250, which utilizes a gate masking member which is etched and the gate oxide beneath the gate undercut to form overhangs. When a substrate is subjected to ion implantation with such a mask, a much shallower concentration of impuri~ies is implanted in the substrate beneath the overhangs than in the substrate region not protected by the masking member. Such a process provides self alignment for the gate and the source and drain regions will be overlapped by thP gate more than with the plain self-aligned gate process. The Miller capacitance will be increased slightly compared to the usual S.A.G. (Self-Aligned Gates) process, but, the likelihood for punchthrough is reduced~
The disadvantage of the process described in the above noted patent is that the amount of undercut for sub-micrometer gate dimensions is uncontrollable. The prior art describes a process for 2-4 ~m gate lengths where the undercut is typically 0.25 to 0.5 ~m on each sideO However, it is obvious that any undercut of a 0.5 ~m gate length will be too significantl e.g., only 300 Angstroms on a side undercut is 12% and is not uniform from wafer to wafer and on an individual wafer because of the isotropic etches required by the prior art.
~ ntion In accordance with an aspect of the invention there is provided a process for controlling the impurity profile distribution in a bady of semiconductor material which includes a conductive layer, comprising the steps of defining a masking member on a laterally extending major surface of said body in a predetermined pattern; etching said surface and said body through said conductive layer using said masking member as a mask so as to form a truncated, pyramidal shaped gate element having sides which - ~a -slope to form taperec? gate edges and ion implanting active regions of said semiconductor circuit using said gate element as a mask so as to form active regions having lighter and shallower degenerately doped p~ortions under said tapered gate edges, a channel region being defined under said gate element between said active regions, the length of said channel region extending between said active regions under said gate element, the length of said channel region between said degenerately doped portions being less than the length of said channel region beneath said degenerately doped portions.
Briefly and in general terms, the present invention describes a process for forming a doped region in a substrate which is in alignment with a circuit memberO
More particularly, the invention includes the steps~of forming a masking member or. a upper layer portion of the substrate, the masking member defining the outline of the circuit member; and etching the layer employing the masking member as a mask to define the circuit member, the etching GO continuiny such that the circuit member includes sloping side faces. ~n impurity is then ion implanted into the substrate so as to form the doped region, the dosage and energy of ions implanted being selected such that ions are partially blocked by the portions of the circuit member beneath the sloping side faces, thereby providing a more light1y doped and more shallow distribution of implanted species in the substrate region under the sloping side faces which is an extension of ~he doped region, than in the doped region.
The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages ~hereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
Brief Description of the Drawings Figure 1 is a cross-sectional view of a silicon-on-sapphire structure according to the prior art;
Figure 2 is a cross-sectional view of a silicon-on-sapphire structure employing the truncated pyramidal gate element according to the present invention~
Figures 3a through 3e are cross-sectional views of a silicon-on-sapphire structure illustrating the sequence of steps for forming the doped source and drain regions in the said layer according to the present inventicn.
Uescription of the Preferred Embodiment Figure 1 is a cross-sectional view of a silicon-on-sapphire structure using a self~aligned gate (S.A.G.) process. The Figure shows the sapphire (A1203~ substrate, a silicon layer thereover with heavily implanted regions (P++ and N~+) shown cross-hatched~ and the shape and position of the ga~e condwctor. The gate oxide is not shown for simplicity, although the gate oxide thickness tgateoX is represented in the Figure, as well as the thickness of the gate t~.
The fabrication process according to the present invention is based upcn an analysis of the submicrometer gate length structure of the depletion layers which is predicted, or analyzed, by such device per-formance computer programs as GEMINI (GEMINI Program, Stanford University E7ec~ronics Laboratory) and others which calculate the e1ectric field distribution in two dimensions in the channel and are capable of using fabrication process parameter data from computer programs such as SUPREM (SUPREM Program, Stanford University Electronics Labroatory~.
If the length of the channel region is somehow increased in the channel region approximately 0.25~m below the Si-SiO2 interface (where the total SOS film thickness is ~ 0.5~m), the conditions for punchthrough are reduced and the short channel behavior of the device can be eliminated under proper design constraints with respect to the channel dopant concentration profiles.
Twrning next to Figure 2, there is shown a cross-sectional view of a CMOS/SOS device fabricated according to the technique of the present invention. It is noted that the gate elements in both the N-MOS and P-MOS transistors are depicted in the cross-sectional view are in the shape of a trapezoidO In three dimensions, the shape of the gate element would be a truncated pyramid. It is noted from Figure 2 that the sides of the pyramid are slopped away from the normal or perpendicular direction to the surface by an angle of ~
where ~ is greater than 30. The truncated portion of the pyramid has a -top major surface with a length equal to "L", approximately 0.5 to 0.75 micronsO The ~hickness of the gate -tg is typically between 3000 and 4000 Angstroms. The length of the base of the pyramid is L~, which is L + 2tg Tan ~. The typical experimental data shows L =
0.7~, (with tg = 3050 Angstroms). The distance between the bottom surface of the gate element and the upper major surface of the silicon 3a structure~ which is equivalent to the thickness of the gate oxide is toX, which is approximately 100 to 350 Angstroms.
The fabrication process according to the present invention focuses upon the masking property of a circuit member, such as the gate conductor, as a function of its thickness with respect to the N+ and P~ ion implants3 and also upon the slope o~ the gate conductor edges deviating from the vertical. Although if the thickness, t, of the gate conductor at any point on the dimension of the gate conductor is less than that required ~o shield~ or mask, the channel region ~rom the N+
or P+ S.A.G. implants, tg, the dopant ions will penetrate into the silicon immediately beneath the Si-SiO2 interface to an extent depending upon the extent that the gate conductor thickness is less than tg~ A
gate conductor with edges that deviate from the vertical by some angle, ~, will therefore have a degenera~ely doped S and D region tha~ will extend beneath the maximum dimension, Lm~ of the gate with a depth distribution that will depend on ~ as shown in the cross-sectional view of the device according to the present invention in Figure 2.
The etch procedure requires a definitely anisotropic characteristic such that the sloped resist edge profile of the gate pattern is faith-fully reproduced in the ga~e conductor. There is no masking member of the gate conductor other than the resist hence there is one less oxidation and etch step than the prior art. The gate oxide (100-350 Angstroms) is not etched. It is most important to point out from this fiyure that the channel dimension at about 0.25~m below the Si-SiO2 interface where punchthrough of the S and D depletion regions was formerly a problem~ is now increased to a dimension, L~ > L. Therefore, the principal source of the short channel behavior of submicrometer MOSFET devices can be eliminated or at least greatly reduced in the structure formed by the process according to the present invention.
6~3 Turning next to the silicon structure itself, it is noted ~hat the source and drain regions are de~ermined by ion implanting through the gate oxide layer with the region under the gate pyramid being masked from the implant by the gate material of thickness, tg. The areas ion implanted are indicated by the cross hatched regions in Figure 2 to indicate that the amount of implantation or concentration of the dopant species is controlled so that some implantation occurs through the thin tapered edges of the gate element to form a lighter and shallower degenerately doped region directly under the tapered edges of the gate adjacent to the top major surface of the silicon semiconductor. The Figure indicates that this shallower degenerately doped region extends into the semiconductor body a distance of approximately 0.25 microns. Most of the ion implantation is implanted into the semiconductor body in the regions not protected by the masking member formed by the gate element. Directly underneath the center portion of the gate element there is effectively no ion implantation in~o the semiconductor body.
The GEMIMI Program can be used to predict the device behavior with respect to the short channel effect and is based similar to the ",3e71 Criterion." (J. R. Brews et al, IEDM Washington9 D.C., December 1979). If L~ or L is large enough such ~ha~ the subthreshold MOSFET
current will have a negligible dependence on the drain supply voltage, VD, the criterion for L or L~ being large enough depends upon the channel dopant conoentration and its pro~ile with respect to depth into the silicon frum the Si-SiO2 interface.
A sloped gate edge connector can readily be fabricated by the technique according to the present invention. An image reversal resist techniquc using electron beam exposure of a positive photo-resist followed by an optical UV flood exposure results in the positiYe photoresist behaving as a negative resist. (W. G. Oldham, E. Heike3 IEEE Trans. EDL-l (10~, 217, 1980). The resist edge profiles using this method are sloped with some angle, ~, from the vertical. If a dry etching technique (Fineline Lithography, Roger Newman ed., North Holland Publishing Co., Amsterdam, 1980 (Chap. 4., R. L. Maddox, M. R. Splinter))9 such as ion milling, reactive ion etching, parallel plate plasma etching, or reactive ion beam etching is used, an etched gate conductor profile with slope of angle, ~, can be faithfully reproduced from the resist profile.
In additiong the characteristic of sloped gate conductor edge profiles allows for a much relaxed step coverage condition in consideration of conductor layers deposited on top of the gate con-ductor pattern which criss-cross and still maintain continuity such as is required for VLSI.
One possible drawback regarding the present configuration is the increased Miller capacitance caused by the gate electrode overlapping the sloped gate edges. This overlap will be equal to X - tg tan ~.
With an angle on the order of 45, the current tg is about 0.3~m.
Therefore, a Miller capacitance of about 30% of the channel gate input capacitance would be the result. However, for submicrometer devices, the gate input capacitance is no longer the dominan~ factor compared to the interconnect capacitance and, hence, the speed of the device would not be nearly as affected as if the situation were directly scaled up to a 4~m gate length~for example. Note also that can be adjusted by the Elec~ron Beam Lithographic, EBL, or other resist processing variables with respect to the image reversal technique ~W. G. 01dham, E. Heinke, IEEE Trans. EDL-l ~10), 217, 1980) such that the overlap capacitance is less than 30%. Also, tg can be adjusted for a reduction. However, reducing the Miller capacitance will reduce L~ and a compromise must be made.
8~ ~46 Turning next to Figures 3a through 3e, there is shown the sequence of steps for forming the gate elements and the implanted source and drain regions according to the present invention.
Turniny first ~o Figure 3a, there is shown a composite of a silicon-on-sapphire structure which may be used for ion implanting according to the present invention. The silicon layer sn the sapphire substrate typically has a thickness between 4500 and 6000 Angstroms. The structure includes a gate oxide 1ayer on the top major surface of the silicon layer, followed by a -polycrystalline silicon (polysilicon~
layer over the oxide layer. The polysilicon layer is typically doped with phosphorous so that it is N+ conductivity and has a ~hickness between 800 and 1200 Angstroms. A molysilicide layer is applied over the P~ or N+ polysilicon layer, and a photoresist layer applied over the molysilicide layer. The use ~f any suitable refractory metal silicide (e.gO tantalum silicide, tungsten silicide or titanium silicide) is also within the scope of the present invention. The use of a poly-silicon-molysilicide layer is used in the pre~erred embodiment because of the greater conductivity provided by such a structure and its suitability for ultra large scale integrated devices. Other conductive layers can be used as well. According to the techniques of the present invention, the photoresist layer is a posi~ive photoresist layer.
Turnin~ next to Fi~ure 3b, there is shown the step in which the photoresist layer is selectively exposed to an electron beam in a predetermined pattern. The layer of photoresist is exposed where the electron beam passes and this photoresist layer portion is to remain after further processing.
The e7ectron beam is directed to the resist substantially normal to the surface of the resist layer. As it penetrates into the thickness of the layer, the electron ~eam scatters, and diverges from the surface.
The net affect of the scattering of the electrons in the resist layer is the exposure of the resist in a cross-section representing a trapezoid such as that shown in Figure 3b. Since the area exposed by the electron beam is typically that of a gate element, or other channel structure in a self-aligned MOS-MIS-MES device, the actual geometric structure exposed in the resist layer is that of a truncated pyramid.
The use of an electron beam for exposure of a positive resist is also described in the article W. G. Oldham, E. Heinke, IEEE Trans. EDL-1 (10), 217, 19~0.
Following exposure to the electron beam, the entire photoresist layer is f100ded with ultraviolet light. The ultraviolet light reacts differently with the portions of the resist exposed by the electron beam ~han the portions which have not been exposed. The net effect is that after the layer of photoresist is etched, the portions which have been exposed to the electron beam remain, such as shown in Figure 3c. The truncated pyramidal resist structure is then used as a mask for removing portions of the conductive layer which do not lie under the mask. The removal of -these portions of the conductor layer is achieved by a standard etching process such as reactive ion etching or ion milling.
The etching process leaves truncated pyramidal elements consisting nf a top layer of resist, followed by a lower conductive layer or layers. Such truncated pyramidal structures lie on the silicon oxide surface of the body as is shown in Figure 3d.
The next process step is to remove the remaining resist la~yer from the top of the pyramid. This is performed by the process of ~ plasma ashing.
The structure which remains is shown in Figure 3e which consists of a truncated pyramidal gate type element which overlies the silicon semiconductor body. Such a structure is then used as a mask for ion implanting the source and drain regions of the sem;conductor body in a self-ali~ned manner as is known in the techniques according to the art. The impurity profiled distribution in the source and drain regions and in the channel after ion implantation is substantially as shown in Figure 3e~ The net effect is that the distance between the source and drain regions are closest at the surface of the semiconductor body and spaced ~urther apart as the distance from the surface increases.
It is noted th~t some implantation occurs in the substrate region below the sloping side faces of the ga~e-type circuit element.
Such implantation results in the formation of a more lightly doped source and drain regions benea~h such side faces, while more heavily doped source and drain regions are provided in the silicon regions unprotected by the masking member. The doses and energy of the ions implanted are so selected such that the ions are partially blocked by ~he portion of the gate structure beneath the sloping side faces, so as to provide a more shallow distribution of the implanted s~ecies in the region directly underneath the sloping side faces than in nther regions.
The result of the formation of the gate element according to the present invention is a self-aligned process in which the distance between the source and the drain regions in the depth of the semi-conductor body (i.e.5 semiconductor regions deeper than 0.25~ from the top major surface) are relatively spaced apart a greater distance than at the surface, thus minimizing the problem of punchthrough.
While the invention has been illustrated and described as embodied in a microelectronic shadow maskiny process for reducing punchthrough, it is not intended to be limited to the details shown, since various modifications and structural changes ~ay be made without departing in any way from the spirit of the present invention.
It will be obvious to those skilled in the art that the semiconductor device according to the present invention can be implemented with various semiconduc~or technologies and different combinations of known process steps, and that the preferred embodiments illustrated here are merely exemplary. The depth of penetration of the various zones and regions and in particular the configuration and distance between the active zones of the transistor devices, as well as the concentrations of dopant species, and/or their concentration profiles, can be chosen depending upon the desired properties. These and other variations can be further elaborated by those skilled in the art without departing from the scope of the present invention.
The present lnvention is moreover not restricted to the particular embodiments of a microelectronic shadow masking process for reducing punchthrough described. For example, it may be pointed out that semi-conduc~or materials other than silicon, for example, A~ BV compounds may be used. Furthermore7 the conductivity types in the embodiment may be interchanged and corresponding to such change, the voltage level and the static or dynamic nature of the signals applied to the various terminals and gates of the device, as well as the voltage sources~ may be suitably selected as desired for a particular application. Other types of semiconductor circuits including bipolar junction field effect transistor, MNOS ~metal electrode-silicon nitride, silicon oxide-semiconductor), MAOS (metal aluminum oxide, silicon oxide, semiconductor), MAS (metal, aluminum oxide, semiconductor), flcating gate FETs, and AMOS FETs (avalanche MOS FETs), may be used as well.
Without further ana1ysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art~ fairly constitutes essential characteristics of the generic or specific aspects of this invention, and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.
What is claimed is:
Claims (22)
1. A process for controlling the impurity profile distribution in a body of semiconductor material which includes a conductive layer, comprising the steps of:
defining a masking member on a laterally extending major surface of said body in a predetermined pattern;
etching said surface and said body through said conductive layer using said masking member as a mask so as to form a truncated, pyramidal shaped gate element having sides which slope to form tapered gate edges; and ion implanting active regions of said semi-conductor circuit using said gate element as a mask so as to form active regions having lighter and shallower degenerately doped portions under said tapered gate edges, a channel region being defined under said gate element between said active regions, the length of said channel region extending between said active regions under said gate element, the length of said channel region between said degenerately doped portions being less than the length of said channel region beneath said degenerately doped portions.
defining a masking member on a laterally extending major surface of said body in a predetermined pattern;
etching said surface and said body through said conductive layer using said masking member as a mask so as to form a truncated, pyramidal shaped gate element having sides which slope to form tapered gate edges; and ion implanting active regions of said semi-conductor circuit using said gate element as a mask so as to form active regions having lighter and shallower degenerately doped portions under said tapered gate edges, a channel region being defined under said gate element between said active regions, the length of said channel region extending between said active regions under said gate element, the length of said channel region between said degenerately doped portions being less than the length of said channel region beneath said degenerately doped portions.
2. A process as defined in claim 1, wherein said step of defining a masking member comprises the steps of:
applying a layer of photoresist to said laterally extending major surface of said body;
exposing said layer of photoresist to an electron beam and ultraviolet light in a predetermined pattern;
etching said layer of photoresist to remove the unexposed portion of said layer.
applying a layer of photoresist to said laterally extending major surface of said body;
exposing said layer of photoresist to an electron beam and ultraviolet light in a predetermined pattern;
etching said layer of photoresist to remove the unexposed portion of said layer.
3. The process defined by claim 1, wherein conductive layer is a refractory metal polysilicon composite.
4. The process defined by claim 3, wherein said refractory metal is molysilicide.
5. The process defined by claim 1 wherein said ion implantation comprises source and drain region implantation.
6. A process as defined in claim 1, wherein said body of semiconductor material includes a gate oxide layer, a polysilicon layer over said oxide layer, and a moly-silicide layer over said polysilicon layer.
7. A process as defined in claim 2, wherein said photoresist is a positive photoresist.
8. A process as defined in claim 2, wherein said step of exposing said layer of photoresist comprises exposing said layer in a pattern of regions where the photoresist is to remain after subsequent processing.
9. A process as defined in claim 2, further comprising the step of subsequently exposing said layer of photoresist with ultraviolet light.
10. A process as defined in claim 6, further comprising the step of developing said layer of photoresist and removing the unexposed portion.
11. A process for fabricating a MOS silicon integrated circuit structure at a predetermined area on a silicon body portion comprising the steps of:
forming a continuous silicon oxide layer on said body portion covering at least one area;
forming a polycrystalline silicon layer on said oxide layer such that said silicon layer is insulated from said body portion at said area;
forming a conducting layer on said polycrystalline silicon layer;
forming a masking layer on said conducting layer;
etching said masking layer to form a masking structure having a predetermined pattern;
etching said conducting layer and said poly-crystalline silicon employing said masking structure as a mask;
whereby a truncated pyramidal shaped gate element having sloping sides is formed on said oxide layer; and ion implanting active regions of said semiconductor circuit using said gate element as a mask so as to form doped regions at opposite ends of said gate element, wherein said doped regions have lighter and shallower degenerately doped portions under said gate element sides so that during operation of said MOS silicon integrated circuit structure, carrier punch-through between said doped regions and beneath said gate element is retarded.
forming a continuous silicon oxide layer on said body portion covering at least one area;
forming a polycrystalline silicon layer on said oxide layer such that said silicon layer is insulated from said body portion at said area;
forming a conducting layer on said polycrystalline silicon layer;
forming a masking layer on said conducting layer;
etching said masking layer to form a masking structure having a predetermined pattern;
etching said conducting layer and said poly-crystalline silicon employing said masking structure as a mask;
whereby a truncated pyramidal shaped gate element having sloping sides is formed on said oxide layer; and ion implanting active regions of said semiconductor circuit using said gate element as a mask so as to form doped regions at opposite ends of said gate element, wherein said doped regions have lighter and shallower degenerately doped portions under said gate element sides so that during operation of said MOS silicon integrated circuit structure, carrier punch-through between said doped regions and beneath said gate element is retarded.
12. The process as defined in claim 11 wherein said conducting layer has a thickness between 3,000 and 4,000 Angstroms.
13. The process as defined in claim 12 wherein said conducting layer is composed of a N+ polysilicon first layer having a thickness between 800 and 1,200 Angstroms, and a refractory metal silicide second layer.
14. A process for controlling the impurity profile distribution in a body of semiconductor material which includes a conductor layer on a major surface thereof, comprising the steps of:
forming a masking layer over said conductive layer;
exposing said masking layer in a predetermined pattern by an electron beam;
subsequently exposing said entire masking layer to ultraviolet light;
etching said masking layer to remove the unexposed portion of said layer;
etching said surface and said body through said conductive layer using said masking member as a mask so as to form a truncated pyramidal shaped element having sloped sides; and ion implanting active regions of said semiconductor circuit using said element as a mask so that said regions are more lightly doped and the implanted dopant distribution is more shallow directly beneath said sloped sides of said elements than in regions away from said masking member thus forming shallow active portions of said active regions at opposite ends of said element, so that a channel is defined under said element and between said active regions, and so that punch-through between said active regions and beneath said shallow active areas is retarded.
forming a masking layer over said conductive layer;
exposing said masking layer in a predetermined pattern by an electron beam;
subsequently exposing said entire masking layer to ultraviolet light;
etching said masking layer to remove the unexposed portion of said layer;
etching said surface and said body through said conductive layer using said masking member as a mask so as to form a truncated pyramidal shaped element having sloped sides; and ion implanting active regions of said semiconductor circuit using said element as a mask so that said regions are more lightly doped and the implanted dopant distribution is more shallow directly beneath said sloped sides of said elements than in regions away from said masking member thus forming shallow active portions of said active regions at opposite ends of said element, so that a channel is defined under said element and between said active regions, and so that punch-through between said active regions and beneath said shallow active areas is retarded.
15. The process defined by claim 14, wherein conductive layer is a refractory metal-polysilicon composite.
16. The process defined by claim 15, wherein said refractory metal is selected from the group consisting of molysilicide, tantalum silicide, tungsten silicide and titanium silicide.
17. The process defined by claim 14, wherein said ion implantation comprises implanting source and drain regions of a field-effect transistor.
18. A process as defined in claim 14, wherein said body of semiconductor material includes a gate oxide layer, a polysilicon layer over said oxide layer, and a refractory metalsilicide layer over said polysilicon layer.
19. A process as defined in claim 14, wherein said masking layer is a positive photoresist.
20. A MOS process for forming source and drain regions in a substrate which includes a gate oxide layer and polysilicon layer comprising the steps of:
defining a masking member on said polysilicon layer in a predetermined pattern;
etching said polysilicon layer to form a gate employing said masking member as a mask, said etching forming a truncated pyramidal gate structure having sloped edge faces, the base of said pyramidal gate structure being disposed on said gate oxide layer;
ion implanting said substrate to form said source and drain regions through said gate oxide, the dosage and energy of ions implanted being selected so that a lower concentration and more shallow distribution of impurities is implanted in substrate regions beneath said sloped edge faces than in substrate regions not protected by said gate structures so that a channel is defined beneath said gate and between said source and drain regions, and so that the length of said channel is shorter near said gate and longer away from said gate; and whereby during subsequent processing steps, said lower concentration of impurities does not substantially diffuse, thereby providing more precise alignment between said gate structure and said source and drain regions.
defining a masking member on said polysilicon layer in a predetermined pattern;
etching said polysilicon layer to form a gate employing said masking member as a mask, said etching forming a truncated pyramidal gate structure having sloped edge faces, the base of said pyramidal gate structure being disposed on said gate oxide layer;
ion implanting said substrate to form said source and drain regions through said gate oxide, the dosage and energy of ions implanted being selected so that a lower concentration and more shallow distribution of impurities is implanted in substrate regions beneath said sloped edge faces than in substrate regions not protected by said gate structures so that a channel is defined beneath said gate and between said source and drain regions, and so that the length of said channel is shorter near said gate and longer away from said gate; and whereby during subsequent processing steps, said lower concentration of impurities does not substantially diffuse, thereby providing more precise alignment between said gate structure and said source and drain regions.
21. A process for forming a MOS field effect transistor on a substrate comprising the steps of:
forming a gate oxide layer on said substrate;
forming a layer of polysilicon over said gate oxide layer;
defining a masking member on said polysilicon layer in a predetermined shape including sloping side faces;
etching said polysilicon layer employing said masking member as a mask to form a gate for said field-effect transistor, including etching said polysilicon layer under said masking member to form said gate with sloping side faces which extend from the sloping said faces of said masking member;
ion implanting said substrate to form source and drain regions by ion implanting through said gate oxide, such that some implantation occurs in the substrate region beneath said sloping side faces of said gate, thereby forming more lightly doped source and drain regions beneath said side faces and more heavily doped source and drain regions in substrate areas unprotected by said masking member so that punch-through between said source and drain regions deep within said substrate is retarded during operation of said field effect transistor; and whereby during subsequent processing steps, the lower concentration of impurities in said more lightly doped source and drain regions does not substantially diffuse beneath said gate, thereby providing more precise alignment between said gate and said source and drain regions.
forming a gate oxide layer on said substrate;
forming a layer of polysilicon over said gate oxide layer;
defining a masking member on said polysilicon layer in a predetermined shape including sloping side faces;
etching said polysilicon layer employing said masking member as a mask to form a gate for said field-effect transistor, including etching said polysilicon layer under said masking member to form said gate with sloping side faces which extend from the sloping said faces of said masking member;
ion implanting said substrate to form source and drain regions by ion implanting through said gate oxide, such that some implantation occurs in the substrate region beneath said sloping side faces of said gate, thereby forming more lightly doped source and drain regions beneath said side faces and more heavily doped source and drain regions in substrate areas unprotected by said masking member so that punch-through between said source and drain regions deep within said substrate is retarded during operation of said field effect transistor; and whereby during subsequent processing steps, the lower concentration of impurities in said more lightly doped source and drain regions does not substantially diffuse beneath said gate, thereby providing more precise alignment between said gate and said source and drain regions.
22. In a process for forming a doped region in a substrate which is in alignment with a circuit member, the improved steps comprising:
forming a masking member on a layer, said masking member defining the outline of said circuit member;
etching said layer employing said masking member as a mask to define said circuit member, said etching continuing such that said circuit member includes sloping side faces;
implanting impurity ions into said substrate so as to form said doped region, the dosage and energy of ions implanted being selected such that ions are blocked by said circuit member with a portion of said impurity dosage allowed to pass through said sloping side faces thereby producing said doped region with a more lightly doped and more shallow distribution of implanted impurity beneath said sloping side faces so that punch-through deep within said substrate is retarded; and whereby in subsequent processing steps said more lightly doped regions do not substantially diffuse beneath said circuit member.
forming a masking member on a layer, said masking member defining the outline of said circuit member;
etching said layer employing said masking member as a mask to define said circuit member, said etching continuing such that said circuit member includes sloping side faces;
implanting impurity ions into said substrate so as to form said doped region, the dosage and energy of ions implanted being selected such that ions are blocked by said circuit member with a portion of said impurity dosage allowed to pass through said sloping side faces thereby producing said doped region with a more lightly doped and more shallow distribution of implanted impurity beneath said sloping side faces so that punch-through deep within said substrate is retarded; and whereby in subsequent processing steps said more lightly doped regions do not substantially diffuse beneath said circuit member.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000469969A CA1200617A (en) | 1981-10-14 | 1984-12-12 | Microelectronic shadow masking process for reducing punchthrough |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/311,206 US4394182A (en) | 1981-10-14 | 1981-10-14 | Microelectronic shadow masking process for reducing punchthrough |
| US311,206 | 1981-10-14 |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000469969A Division CA1200617A (en) | 1981-10-14 | 1984-12-12 | Microelectronic shadow masking process for reducing punchthrough |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1194613A true CA1194613A (en) | 1985-10-01 |
Family
ID=23205876
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000407811A Expired CA1194613A (en) | 1981-10-14 | 1982-07-22 | Microelectronic shadow masking process for reducing punchthrough |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US4394182A (en) |
| JP (1) | JPS5875871A (en) |
| CA (1) | CA1194613A (en) |
| DE (1) | DE3237539A1 (en) |
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| US4514896A (en) * | 1981-03-25 | 1985-05-07 | At&T Bell Laboratories | Method of forming current confinement channels in semiconductor devices |
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| JPS61127174A (en) * | 1984-11-26 | 1986-06-14 | Toshiba Corp | Manufacture of semiconductor device |
| KR970003903B1 (en) * | 1987-04-24 | 1997-03-22 | Hitachi Mfg Kk | Semiconductor device and fabricating method thereof |
| EP0412701B1 (en) * | 1989-07-31 | 1996-09-25 | Canon Kabushiki Kaisha | Thin film transistor and preparation thereof |
| FR2651068B1 (en) * | 1989-08-16 | 1994-06-10 | France Etat | PROCESS FOR PRODUCING SILICON-ON-INSULATOR MOS MESA TRANSISTOR |
| US5474941A (en) * | 1990-12-28 | 1995-12-12 | Sharp Kabushiki Kaisha | Method for producing an active matrix substrate |
| DE69125260T2 (en) * | 1990-12-28 | 1997-10-02 | Sharp Kk | A method of manufacturing a thin film transistor and an active matrix substrate for liquid crystal display devices |
| JP2634505B2 (en) * | 1991-06-17 | 1997-07-30 | シャープ株式会社 | Thin film transistor and method of manufacturing the same |
| US6964890B1 (en) | 1992-03-17 | 2005-11-15 | Semiconductor Energy Laboratory Co., Ltd. | Semiconductor device and method for forming the same |
| TW403972B (en) * | 1993-01-18 | 2000-09-01 | Semiconductor Energy Lab | Method of fabricating mis semiconductor device |
| KR100267755B1 (en) * | 1993-03-18 | 2000-10-16 | 김영환 | Manufacturing method of thin film transistor |
| US5830787A (en) * | 1993-03-18 | 1998-11-03 | Lg Semicon Co., Ltd. | Method for fabricating a thin film transistor |
| US5401982A (en) * | 1994-03-03 | 1995-03-28 | Xerox Corporation | Reducing leakage current in a thin-film transistor with charge carrier densities that vary in two dimensions |
| FR2724769B1 (en) * | 1994-09-16 | 1996-12-06 | Thomson Csf | METHOD FOR PRODUCING LASER DIODES WITH SURFACE EMISSION |
| TW362289B (en) * | 1997-12-22 | 1999-06-21 | United Microelectronics Corp | Manufacturing method of metal oxide semiconductor field effect transistor |
| US6346451B1 (en) | 1997-12-24 | 2002-02-12 | Philips Electronics North America Corporation | Laterial thin-film silicon-on-insulator (SOI) device having a gate electrode and a field plate electrode |
| JP3883706B2 (en) * | 1998-07-31 | 2007-02-21 | シャープ株式会社 | Etching method and method of manufacturing thin film transistor matrix substrate |
| ATE252889T1 (en) | 1998-08-19 | 2003-11-15 | Skyepharma Canada Inc | INJECTABLE AQUEOUS PROPOFOL DISPERSIONS |
| US6617644B1 (en) * | 1998-11-09 | 2003-09-09 | Semiconductor Energy Laboratory Co., Ltd. | Semiconductor device and method of manufacturing the same |
| US6909114B1 (en) * | 1998-11-17 | 2005-06-21 | Semiconductor Energy Laboratory Co., Ltd. | Semiconductor device having LDD regions |
| US6365917B1 (en) | 1998-11-25 | 2002-04-02 | Semiconductor Energy Laboratory Co., Ltd. | Semiconductor device |
| EP1006589B1 (en) * | 1998-12-03 | 2012-04-11 | Semiconductor Energy Laboratory Co., Ltd. | MOS thin film transistor and method of fabricating same |
| EP2256808A2 (en) | 1999-04-30 | 2010-12-01 | Semiconductor Energy Laboratory Co, Ltd. | Semiconductor device and manufacturing method therof |
| JP2001035808A (en) * | 1999-07-22 | 2001-02-09 | Semiconductor Energy Lab Co Ltd | Wiring and its creating method, semiconductor device having this wiring, and dry-etching method therefor |
| US6541294B1 (en) * | 1999-07-22 | 2003-04-01 | Semiconductor Energy Laboratory Co., Ltd. | Semiconductor device and manufacturing method thereof |
| TW480554B (en) * | 1999-07-22 | 2002-03-21 | Semiconductor Energy Lab | Semiconductor device and manufacturing method thereof |
| US6646287B1 (en) | 1999-11-19 | 2003-11-11 | Semiconductor Energy Laboratory Co., Ltd. | Semiconductor device with tapered gate and insulating film |
| US6362033B1 (en) * | 1999-12-14 | 2002-03-26 | Infineon Technologies Ag | Self-aligned LDD formation with one-step implantation for transistor formation |
| TW495854B (en) * | 2000-03-06 | 2002-07-21 | Semiconductor Energy Lab | Semiconductor device and manufacturing method thereof |
| TW513753B (en) * | 2000-03-27 | 2002-12-11 | Semiconductor Energy Lab | Semiconductor display device and manufacturing method thereof |
| TWI286338B (en) * | 2000-05-12 | 2007-09-01 | Semiconductor Energy Lab | Semiconductor device and manufacturing method thereof |
| TW480576B (en) * | 2000-05-12 | 2002-03-21 | Semiconductor Energy Lab | Semiconductor device and method for manufacturing same |
| TW501282B (en) * | 2000-06-07 | 2002-09-01 | Semiconductor Energy Lab | Method of manufacturing semiconductor device |
| US6690034B2 (en) | 2000-07-31 | 2004-02-10 | Semiconductor Energy Laboratory Co., Ltd. | Light emitting device |
| JP5046452B2 (en) * | 2000-10-26 | 2012-10-10 | 株式会社半導体エネルギー研究所 | Method for manufacturing semiconductor device |
| JP4954366B2 (en) * | 2000-11-28 | 2012-06-13 | 株式会社半導体エネルギー研究所 | Method for manufacturing semiconductor device |
| SG138468A1 (en) * | 2001-02-28 | 2008-01-28 | Semiconductor Energy Lab | A method of manufacturing a semiconductor device |
| US20030081906A1 (en) * | 2001-10-26 | 2003-05-01 | Filhaber John F. | Direct bonding of optical components |
| KR100493018B1 (en) * | 2002-06-12 | 2005-06-07 | 삼성전자주식회사 | Method for fabricating a semiconductor device |
| US7319236B2 (en) * | 2004-05-21 | 2008-01-15 | Semiconductor Energy Laboratory Co., Ltd. | Semiconductor device and electronic device |
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| JP5130834B2 (en) * | 2007-09-05 | 2013-01-30 | ソニー株式会社 | Semiconductor device and manufacturing method thereof |
| US8298881B2 (en) | 2010-06-28 | 2012-10-30 | International Business Machines Corporation | Nanowire FET with trapezoid gate structure |
| US10903330B2 (en) * | 2013-11-27 | 2021-01-26 | General Electric Company | Tapered gate electrode for semiconductor devices |
| JP5977804B2 (en) * | 2014-11-18 | 2016-08-24 | 株式会社半導体エネルギー研究所 | Method for manufacturing semiconductor device |
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| US4090289A (en) * | 1976-08-18 | 1978-05-23 | International Business Machines Corporation | Method of fabrication for field effect transistors (FETs) having a common channel stopper and FET channel doping with the channel stopper doping self-aligned to the dielectric isolation between FETS |
| US4114256A (en) * | 1977-06-24 | 1978-09-19 | Bell Telephone Laboratories, Incorporated | Reliable metal-to-junction contacts in large-scale-integrated devices |
| US4149904A (en) * | 1977-10-21 | 1979-04-17 | Ncr Corporation | Method for forming ion-implanted self-aligned gate structure by controlled ion scattering |
| US4182023A (en) * | 1977-10-21 | 1980-01-08 | Ncr Corporation | Process for minimum overlap silicon gate devices |
| US4268951A (en) * | 1978-11-13 | 1981-05-26 | Rockwell International Corporation | Submicron semiconductor devices |
| US4198250A (en) * | 1979-02-05 | 1980-04-15 | Intel Corporation | Shadow masking process for forming source and drain regions for field-effect transistors and like regions |
| US4319395A (en) * | 1979-06-28 | 1982-03-16 | Motorola, Inc. | Method of making self-aligned device |
| US4329186A (en) * | 1979-12-20 | 1982-05-11 | Ibm Corporation | Simultaneously forming fully implanted DMOS together with enhancement and depletion mode MOSFET devices |
| US4285761A (en) * | 1980-06-30 | 1981-08-25 | International Business Machines Corporation | Process for selectively forming refractory metal silicide layers on semiconductor devices |
-
1981
- 1981-10-14 US US06/311,206 patent/US4394182A/en not_active Expired - Lifetime
-
1982
- 1982-07-22 CA CA000407811A patent/CA1194613A/en not_active Expired
- 1982-10-04 JP JP57176047A patent/JPS5875871A/en active Pending
- 1982-10-09 DE DE19823237539 patent/DE3237539A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5875871A (en) | 1983-05-07 |
| US4394182A (en) | 1983-07-19 |
| DE3237539A1 (en) | 1983-07-21 |
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