|Publication number||US3783825 A|
|Publication date||Jan 8, 1974|
|Filing date||Mar 1, 1972|
|Priority date||Mar 5, 1971|
|Also published as||CA953618A, CA953618A1, DE2210371A1, DE2210371B2|
|Publication number||US 3783825 A, US 3783825A, US-A-3783825, US3783825 A, US3783825A|
|Inventors||Akasaki I, Kobayasi H|
|Original Assignee||Matsushita Electric Ind Co Ltd|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (5), Referenced by (37), Classifications (14)|
|External Links: USPTO, USPTO Assignment, Espacenet|
United States Patent 1 91 Kobayasi et al.
[ Jan. 8, 1974  Inventors: l-liroyuki Kobayasi; lsamu Akasaki,
both of Osaka, Japan  Assignee: Matsushita Electric Industrial Company, Limited, Osaka, Japan  Filed: Mar. 1, 1972  Appl. No.: 230,661
 Foreign Application Priority Data Mar. 5, 1971 Japan 46/12067  US. Cl. 118/422, 23/273 SP, 148/1.5, 148/172  Int. C1. B056! 3/00, BOld 9/00  Field of Search 118/58, 415, 421,
118/422, 423, 426, 429; 148/15, 171, 172; 23/273 SP, 301 SP  References Cited UNITED STATES PATENTS 3,565,702 2/1971 Nelson 148/172 3,665,888 5/1972 Bergh et a1. 118/58 3,677,228 7/1972 Panish et a1. 1 18/422 3,697,330 10/1972 Minden et a1. 23/273 SP 3,705,825 12/1972 Touchy et al 148/15 Primary Examiner-Louis K. Rimrodt [5 7] ABSTRACT An apparatus for the liquid-phase epitaxial growth of multi-layer wafer comprising a refractory furnace tube, a boat placed in the furnace tube and having a plurality of bathes which are aligned in the longitudinal direction of the furnace tube and respectively carry solutions each containing semiconductive substances, and a holding member for holding a substrate which is arranged to succeedingly flood the substrate with the solutions so as to epitaxially grow a multilayer wafer on the substrate. The holding member arranged to upset the substrate upon picking-up or separating of the substrate from the solution so that the solution remained on the substrate is dropped from the substrate whereby unwanted mixing of the solutions neighbouring each other can be avoided.
I 1 Claim, 9 Drawing Figures PAIENTEDJAN 81914 I 3.783.825
sum 1 or 3 Fig. PRIOR ART minim m Bum 3.783.825
SHEET 2 OF 3 APPARATUS FOR THE LIQUID-PHASE EPITAXIAL GROWTH or MULTI-LAYER WAFERS The present invention relates to apparatus for making semiconductor wafers, and more particularly, to an apparatus for epitaxially growing a semiconductive multi-layer wafer on a substrate.
Several apparatus for making multi-layer semiconductor wafers have been devised, one of which is an apparatus disclosed on page 109 of the Applied Physics Letters, vol. 17, No. 3, 1970. This apparatus includes a plurality of baths carrying solutions each containing substances to form one layer of the multi-layer, and a holder for holding a substrate and for successively dipping in the baths the substrate so as to deposit and grow the substances on the substrate in the form of the multilayer. Since the apparatus achieves the epitaxial growth step for each of the multiple layers without exposing of the substrate to the atmosphere, unwanted pollution of the layers is avoided.
However, a problem is still encountered in that one solution carried by one of the baths is liable to unwantedly remain on the substrate and be delivered to the succeeding bath thereby to cause it to pollute another solution carried in the succeeding bath.
It is accordingly an object of the present invention to provide an improved apparatus for making a multilayer wafer.
It is another object of the invention to provide an apparatus for the liquid-phase growth of a multi-layer wafer which can avoid unwanted pollution of the solution containing substances to be grown.
It is another object of vthe invention to provide an apparatus for the liquid-phase epitaxial growth of a multilayer wafer which is readily controlled in temperature Further objects, features and advantages of the invention will become apparent from a consideration of the following description, the appended claims, and the accompanying drawings in which:
FIG. 1 is a longitudinal sectional view of a conventional apparatus;
FIG. 2 is a cross-sectional view of the FIG. 1, taken along a line 2-2;
FIG. 3 is a longitudinal sectional view of an embodiment of the present invention;
FIGS. 4A and 4B. are cross-sectional views taken along a line 4-4 shown in FIG. 3;
FIG. 5 is a schematic view of another embodiment of the invention;
FIG. 6 is a longitudinal sectional view of the apparatus of FIG. 5; I
FIGS. 7A and 7B are cross-sectional views taken along a line 7--7 shown in FIG. 6;
Corresponding characters of reference designate like parts in the several views.
Referring now to the drawings and'particularly to FIGS. 1 and 2, there is shown an apparatus described apparatus of on page 109 of the Applied Physics Letters, vol. 7, No. 3, 1971, which comprises a refractory furnace tube made of a refractory material such as quartz. The furnace tube 20 may be heated by a heating coil (not shown) surrounding the furnace tube 20. In the furnace tube 20 is placed a columnar boat 21 which has a bore 22 extending therethrough and a plurality of, in this case, four bathes 23a, 23b, 23c and 23d on its upper portion. Each of the baths communicate with the bore The temperature in the vicinity of the substrate 25 is detected through the thermocouple 28. A push rod 29 is connected to a side wall of the boat 21. The push rod I 29 is arranged to be movable in the longitudinal direction of the furnace tube 20. The baths 23a, 23b, 23c and 23d respectively carry solutions 30a, 30b, 30c and 30d each containing semiconductive substances in preselected proportions.
In operation, the boat 21 is so positioned as to separate the substrate 25 from any of the solutions 30a, 30b, 30c and 30d. The solution 30a is first preheated to about 800 C and, then the boat 21 is slid to the left of the figure through the push rod 29 until the substrate 25 is flooded with the s0luti0n30a. Thereafter, the temperature of the solution 30a is lowered to about 790 C so that the semiconductive substances contained in the solution 30a precipitate and an epitaxial layer grows on the substrate 25. The thickness of the epitaxial layer is in accord with degree of the cooling of the solution 30a. Upon completion of the epitaxial growth, the boat 21 is further slid through the push rod 29 until the substrate 25 is flooded .with the solution 30b while controlling the temperature of the solution 30b. The solution 30b is then cooled by either several or 10 and several degrees of centigradeso as to precipi-' tate the substances in the solution, whereby another epitaxial layer grows on the epitaxial layer previously grown. Similar procedures to the above-stated procedures are succeedingly repeated so as to produce a multi-layer wafer on the substrate 25.
The above-mentioned apparatus is capable of making a multi-layer wafer with-a plurality of epitaxial layers each having a desired thickness by controlling the, temperature of the substrate and the solution. Furthermore, since all the steps for making the multi-layer wafer are performed without exposing the substrate to the atmosphere, unwanted pollution of the epitaxial layers is avoided. It'is, however, a problem that a small amount of solution remains on the epitaxial layer after the completion of the growth of the epitaxial layer. The solution remained on the epitaxial layer is unwantedly delivered to the succeeding bath and mixed with the solution in the succeeding bath, whereby the solution is polluted or proportions of the contents of the solution is changed. In order to avoid this problem, an improved apparatus for the epitaxial growth of a multi-layer wafer is provided by the present invention. 7
In FIGS. 3, 4a and 4b, a preferred embodiment of the invention is illustrated, comprising a refractory furnace tube 40 made of a refractory material such as-quartz. The furnace tube 40 is heated by a heater such as heating coil (not shown) and arranged rotatable about its central axis. In the furnace tube 40 is placed a cylindrical boat 41 which may be made of graphite and may be formed into another form, if desired. The boat 41 is provided on its peripheral wall with a groove 42 extending in the longitudinal direction of the boat 41. A claw member 43 is inserted into the groove 42, the claw member 43 being secured to the furnace tube 40 so that the boat 41 is fixed to the furnace tube 40 in the circumferential direction of the tube 40 but slidable in the longitudinal direction. The boat 41 is provided with a bore 44 extending therethrough in the longitudinal direction and having, in this case, a rectangular section. The boat 41 has two baths 45a and 45b which communicate with the bore 44 and respectively carry solutions 46a and 46b each containing semiconductive substances in preselected proportions. If desired, the boat 41 may have other baths. The boat 41 has another bore 47 extending parallel to the bore 44. Into the bore 44 is snugly and slidably inserted a columnar holding member 48 which holds a substrate 50 in its recess portion 51 formed to face the baths 45. The substrate 50 is secured to the recess portion by means of a clamping member 52. A stopper 53 prevents the holding member 48 from moving to the left of this figure. A thermocouple 54 is inserted into the bore 47 of the boat 41 to detect the temperature in the vicinity of the substrate 50. A push rod 55 is connected to one side wall of the boat 41 to move the boat 41 to the left. In operation, the boat is first so positioned that the substrate 50 faces and overlie the bath 45a carrying the solution 46a as shown in FIGS. 3 and 4. The substrate may be positioned against the utmost left end of the boat 41, when the substances in the solution 46a will evaporate at a relatively low temperature. The furnace tube 40 is then heated by the heater so as to preheat the solution 46a and the substrate 52 to a predetermined temperature. Thereafter, the furnace tube 40 together with the boat 41 are rotated through 180 about the central axis of the furnace tube 40 as shown in FIG. 48.
Being apparent from the FIG. 4B, the substrate 50 is flooded with the solution 46a. The temperature of the furnace tube 40 is reduced so as to cool the solution 460 whereby the substances dissolved in the solution 46a precipitate to deposit and grow on the substrate 50 in the form of a first epitaxial layer. When the thickness of the first epitaxial layer reaches a predetermined value the furnace tube 40 is rotated through 180 about the central axis so as to permit the boat 41 to be restored to a position as shown in FIG. 4A whereby the substrate 50 is separated from the solution 46a. Then, the boat 41 is slid to the right by the push rod 55, while controlling the temperature of the solution and the substrate 50, until the substrate faces and overlies the bath 45b carrying the solution 46b. The furnace tube 40 is then rotated through l80 about its central axis so that the boat 41 is rotated and the substrate 50 and the first epitaxial layer are flooded with the solution 461;. The temperature of the furnace tube 40 is then reduced to permit the substances contained in the solution 46b precipitate to deposit and grow on the first epitaxial layer in the form of a second epitaxial layer. Upon completion of the growth of the second epitaxial layer, the furnace tube 40 is rotated through 180 about the central axis to separate the substrate 50 from the solution 46b. A desired number of baths may be provided and the same procedure as the above described may be repeated so as to succeedingly grow epitaxial layers overlying one another in the form of a multilayer wafer.
In this instance, it is to be noted that the cylindrical boat 41 may be arranged to be slidable on the inner peripheral wall of the furnace tube 40 in the circumferential direction of the furnace tube 40, if desired, by omitting the claw member 43.
It is now apparent from the above description that when the boat 41 is slid to permit the substrate to face and overlie the succeeding solution, the substrate 50 and the recess portion 51 are upset with the result that the solution contacted with the substrate 50 during the epitaxial growth is completely dropped from the substrate 50 whereby the unwanted'mixing between the solutions neighbouring each other can be avoided.
Referring now to FIG. 5, there is shown a main portion of another embodiment of the present invention, which comprises a boat 41 having two baths 45a and 45b each carrying a solution containing semiconductive substances. On shoulder portions of the boat 41 opposite to each other stand pair of journal members and 60 each of which has a bore in its central portion. A columnar holding member 48 is journaled on the journal members 60 and 60. The holding member 48 has a projection 51 having a top end for carrying a substrate 50 on which a multi-layer wafer is to be grown. The projection 51 should have such a large height that the end portion thereof passes through the bath 45a or 45b when the holding member is rotated through one rotation.
The above-described arrangement is positioned in a refractory furnace tube 40 as shown in FIG. 6.
In operation, the holding member 48 first so positioned as to separate the substrate 50 from the solution 46a as shown in FIG. 7A. The furnace tube 40 is then heated by the heater so as to preheat the solution 460 and the substrate 50 to a predetermined temperature. Thereafter, the holding member 48 is rotated so as to dip the substance 50 into the solution 46a as shown in FIG. 7B. The temperature of the furnace tube 40 is reduced so as to cool the solution 46a whereby the substances dissolved in the solution 460 precipitate to deposit and grow on the substrate in the form of an epitaxial layer. When the thickness of the epitaxial layer reaches a predetermined value, the holding member 48 is rotated so as to place the substrate in the initial position. Then, the holding member 48 is slided on the bore of the journal members-60 and 60 until the substrate 50 overlies the succeeding solution 46b, while the temperatures of the solution 46b and the substrate 50 are controlled. The holding member 48 is again rotated about its central axis so as to dip the substrate 50 and the previously grown epitaxial layer into the solution 46b. The temperature of the solution 46a is then reduced thereby to cause the substances contained in the solution 46b to precipitate to deposit and grow on the previously grown epitaxial layer. Upon completion of the growth of the following epitaxial layer, the holding member 48 is rotated so as to separate the substance 50 from the solution 46b. A desired number of baths maybe, of course, provided and the same procedure as the above-described is repeated thereby to succeedingly grow a desired number of epitaxial layers overlying one another in the form of a multi-layer.
By using the apparatus shown in FIGS. 3, 4A and 43, several method of making a multi-layer wafer were performed as described in the following examples:
EXAMPLE I A plate of n-GaAs crystalline was used as the substrate 50. The solution 46a included a certain amount of gallium as a solvent, and gallium arsenide of such an amount that a desired amount of gallium arsenide precipitate by reducing the temperature of the solution.
The solution 46a further included aluminium of 0.15 percent by weight of the solvent of gallium and a small amount of silicon as impurities. The solution 46b included gallium as a solvent, and gallium arenide of such an amount that a desired amount of gallium arsenide precipitate through reducing the temperature of the solution 46b. The solution 46b further included aluminium of 0.3 percent by weight of the solvent of gallium and a small amount of silicon as impurities. Before dipping the substrate 50 into the solution 46a, the substrate 50 and the solution 46a were preheated to about 860 C. The furnace tube 40 was then rotated so as to contact the substrate 50 with the solution 46a, and the solution 46a and the substrate 50 were first cooled through a rate C/minute and further cooled through another rate of 2 C/minute thereby to grow a first epitaxial layer of GaAlAs crystal with Si impurity. The first epitaxial layer therefore had a region of p-type and another region of n-type through the behavior of the silicon impurity. Upon completion of the abovedescribed growth of the first epitaxial layer, the furnace tube 40 was rotated so as to separate the substrate 50 from the solution 46a and slid in a direction of the central axis of the furnace tube 40 so as to permit the substrate 50 to face and overlie the solution 46b. The same procedure as for the first epitaxial layer was repeated so as to produce a second epitaxial layer on the first epitaxial layer of GaAlAs crystal. The second epitaxial layer also had p-type and n-type regions. The first epitaxial layer of GaAlAs crystal included AlAs component in percent of mol fraction and the second epitaxial layer of GaAlAs included the AlAs component in 50 percent of mol fraction. Furthermore, the second epitaxial layer has a wider forbidden band than the first epitaxial layer so that light rays produced in the forbidden band in the first epitaxial layer may be mostly radiated without being absorbed in the second layer when the multi-layer wafer is utilized for a luminous element.
EXAMPLE ll A plate of n-type GaP crystal with a large amount of lattice defects was used as the substrate 50. The solution 46a contained a solvent of gallium and a solute of gallium phosphide of such an amount that a desired amount of gallium phosphide precipitate through reducing the temperature of the solution 46a. The solution 46a further contained tellurium of 0.01 mol percent of the solvent as an impurity. The solution 46b contained a solvent of gallium phosphide, a solute of gallium of the same amount as the solution 46a, and a zinc of 0.02 mol percent of the solvent as an impurity.
The above-mentioned arrangement similarly operated except that the solution and the substrate were preheated to about l,000 C and cooled at a rate of 1 1 C/min. As a result, a wafer was obtained, which includes a first epitaxially layer of n-Gap and a second epitaxial layer of p-GaP. A p-n junction was formed between the first and second layers. The p-n junction radiates a green or yellow light ray when exited by electric energy.
EXAMPLE 1]] The boat 41 had, in this case, three baths. A plate of gallium arsenide was used for the substrate 50. First and third solutions respectively contained a solvent of gallium and a solute of gallium arsenide of such an amount as to saturate the solution at about 850 C. The
solutions further contained aluminium of 0.02 percent by weight of the solvent and a trace of impurity of zinc and tin. A second solution contained a solvent galliumand a solute of gallium arsenide of such any amount as to saturate the solution at about 850 C. The second solution further contained a trace of an impurity of silicon.
The above-described arrangement was operated in a manner similar to Example ll. The resultant wafer radiated laser-ray having spectrum with a peak at 1.45 eV when the wafer was used for a Fabry-Perot type semiconductive laser.
EXAMPLE lV Even if the surface of the substrate is contaminated or contains a lot of defects or impurities, a preferred semiconductive wafer was obtained through the following procedure.
A first solution contained a solvent, a solute of the same substance as one constituting the substrate. The amount of the solute was selected so as not to saturate the first solution when the first solution was preheated. Thus, the substance in the surface of the substrate was dissolved until the substance saturate the first solution so that the surface was cleared, when the substrate was dipped into the solution. Thereafter, the same procedure as the preceding Examples was repeated so as to produce a plurality of epitaxial layers on the thus cleaned surface of the substrate.
It is apparent from the foregoing description and Examples that the apparatus of the present invention is capable of avoiding an unwanted mixing between the source solutions neighboring each other through the rotation of the holding member to upset the substrate so as to remove the solution remained on the substrate before the succeeding step. 7
Furthermore, since the apparatus grows a plurality of epitaxial layers on a substrate without exposing the substrate to the atmosphere, unwanted pollution of the surface of the substrate can be avoided. ln addition, since the whole steps for the apparatus are achieved by controlling only one furnace tube, the temperature controlling of the solution and the substrate and-the thickness controlling of the epitaxial layer is readily performed.
The apparatus for the epitaxial growth of multi-layer wafers described above are understood illustrative apparatus only and that the invention is not to be limited to the specific construction and arrangement shown.
What is claimed is:.
1. An apparatus for depositing on a substrate successive epitaxial layers of crystalline semiconductive material from the liquid phase, which comprises;
a refractory furnace tube horizontally arranged;
heating means associated'with said tube;
a boat disposed in said furnace tube with the longitudinal axis of said, boat extending approximately parallel to the longitudinal axis of said tube;
means defining, on an upper surface of said boat, at least two cavities confining therein separate baths of said semiconductive material in molten solutions, said cavitiesbeing aligned in a direction parallel to the central longitudinal axis of said furnace tube;
support plates provided at the opposite ends of said boat and extending upwardly from the upper surface of the boat and embracing said cavities therebetween;
means defining a bore in each of said support plates,
said bores being in alignment; and
a columnar holding member rotatably slidably 8 movement of said holding member and being alignable with said cavities, said projection extending outward from said holding members a sufficient distance so that when said holding member is rosubstrate can be brought into contact with a solution in a cavity with which said projection is aligned'and subsequently can be moved out of contact with that solution. 7
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|U.S. Classification||118/426, 118/421, 257/E21.117, 117/57|
|International Classification||C30B19/06, H01L21/02, H01L21/208, C30B19/00|
|Cooperative Classification||C30B19/061, C30B19/062, H01L21/2085|
|European Classification||C30B19/06D, H01L21/208C, C30B19/06F|