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Publication numberUS20010046088 A1
Publication typeApplication
Application numberUS 08/991,442
Publication dateNov 29, 2001
Filing dateDec 16, 1997
Priority dateFeb 14, 1994
Also published asUS6322220
Publication number08991442, 991442, US 2001/0046088 A1, US 2001/046088 A1, US 20010046088 A1, US 20010046088A1, US 2001046088 A1, US 2001046088A1, US-A1-20010046088, US-A1-2001046088, US2001/0046088A1, US2001/046088A1, US20010046088 A1, US20010046088A1, US2001046088 A1, US2001046088A1
InventorsNaoto Sano, Chidane Ouchi
Original AssigneeNaoto Sano, Chidane Ouchi
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Exposure apparatus and device manufacturing method using the same
US 20010046088 A1
Abstract
An exposure apparatus includes a first dispersing element for dispersing a substantially parallel laser light, from a laser, with respect to wavelength to provide lights of wavelength units, a first optical system for collecting each light of a wavelength unit from the first dispersing element, a wavelength selecting device for passing a predetermined wavelength region of light, of the lights of wavelength units each being collected by the first optical system, a second optical system for receiving the light from the wavelength selecting device and providing parallel lights of wavelength units, and a second dispersing element for combining the parallel lights of wavelength units from the second optical system, the second dispersing element having substantially the same angular dispersion as of the first dispersing element and a direction of dispersion opposite to that of the first dispersing element.
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Claims(21)
What is claimed is:
1. An exposure apparatus, comprising:
a first dispersing element for dispersing a substantially parallel laser light, from a laser, with respect to wavelength to provide lights of wavelength units;
a first optical system for collecting each light of a wavelength unit from said first dispersing element;
wavelength selecting means for passing a predetermined wavelength region of light, of the lights of wavelength units each being collected by said first optical system;
a second optical system for receiving the light from said wavelength selecting means and providing parallel lights of wavelength units; and
a second dispersing element for combining the parallel lights of wavelength units from said second optical system, said second dispersing element having substantially the same angular dispersion as of said first dispersing element and a direction of dispersion opposite to that of said first dispersing element.
2. An apparatus according to
claim 1
, wherein said wavelength selecting means has a slit.
3. An apparatus according to
claim 2
, wherein said wavelength selecting means has a variable region for passing light.
4. An apparatus according to
claim 3
, wherein each of said first and second dispersing elements has a prism.
5. An apparatus according to
claim 3
, wherein each of said first and second dispersing element has a diffraction grating.
6. An exposure apparatus, comprising:
a dispersing element for dispersing a laser light with respect to wavelength;
an optical system for collecting each laser light of a wavelength unit, being dispersed by said dispersing element; and
wavelength selecting means having a portion for blocking each collected laser light, and for changing a band width of light to be provided thereby, by changing said blocking portion.
7. An apparatus according to
claim 6
, wherein said dispersing element, said optical system and said wavelength means are disposed within a resonator.
8. An apparatus according to
claim 7
, further comprising a Brewster window for transforming the laser light into a linearly polarized light and a reflector for directing the laser light back into a chamber, both being provided in said resonator.
9. An apparatus according to
claim 6
, wherein said dispersing element has at least one of a prism and a diffraction grating.
10. An exposure apparatus, comprising:
a first unit serviceable to provide laser light of a spectral width smaller than a natural emission spectrum; and
a second unit interchangeable with said first unit and serviceable to set a spectral width of laser light at the natural emission spectrum.
11. A device manufacturing method for manufacturing a device by using an apparatus as recited in any one of claims 1-10.
12. An illumination apparatus, comprising:
a first dispersing element for dispersing a substantially parallel laser light, from a laser, with respect to wavelength to provide lights of wavelength units;
a first optical system for collecting each light of a wavelength unit from said first dispersing element;
wavelength selecting means for passing a predetermined wavelength region of light, of the lights of wavelength units each being collected by said first optical system;
a second optical system for receiving the light from said wavelength selecting means and providing parallel lights of wavelength units; and
a second dispersing element for combining the parallel lights of wavelength units from said second optical system, said second dispersing element having substantially the same angular dispersion as of said first dispersing element and a direction of dispersion opposite to that of said first dispersing element.
13. An apparatus according to
claim 12
, wherein said wavelength selecting means has a slit.
14. An apparatus according to
claim 13
, wherein said wavelength selecting means has a variable region for passing light.
15. An apparatus according to
claim 12
, wherein each of said first and second dispersing elements has a prism.
16. An apparatus according to
claim 12
, wherein each of said first and second dispersing element has a diffraction grating.
17. A laser apparatus, comprising:
a dispersing element for dispersing a laser light with respect to wavelength;
an optical system for collecting each laser light of a wavelength unit, being dispersed by said dispersing element; and
wavelength selecting means having a portion for blocking each collected laser light, and for changing a band width of light to be provided, by changing said blocking portion.
18. An apparatus according to
claim 17
, wherein said dispersing element, said optical system and said wavelength means are disposed within a resonator.
19. An apparatus according to
claim 18
, further comprising a Brewster window for transforming the laser light into a linearly polarized light and a reflector for directing the laser light back into a chamber, both being provided in said resonator.
20. An apparatus according to
claim 17
, wherein said dispersing element has at least one of a prism and a diffraction grating.
21. A laser apparatus, comprising:
a first unit serviceable to provide laser light of a spectral width smaller than a natural emission spectrum; and
a second unit interchangeable with said first unit and serviceable to set a spectral width of laser light at the natural emission spectrum.
Description
FIELD OF THE INVENTION AND RELATED ART

[0001] This invention relates to an exposure apparatus and a device manufacturing method. More particularly, the invention is concerned with an exposure apparatus and a device manufacturing method, suitably usable for manufacture of devices such as ICs, LSIs, CCDs, liquid crystal panels or magnetic heads, for example.

[0002] With the increasing degree of integration of a semiconductor device, exposure apparatuses of high resolution and having a large exposure area are desired. As an apparatus which meets these requirements, a scan type reduction projection exposure apparatus for exposing a mask and a wafer while scanning them has attracted a large attention.

[0003] On the other hand, in the point of reducing the resolvable line width, use of shorter wavelength light as exposure light is desired. In this respect, use of an excimer laser, for example, which emits intense light in the deep ultraviolet region, in a scan type reduction projection exposure apparatus has been proposed.

[0004] However, as regards the emission spectrum of an excimer laser, in a case of a KrF excimer laser, it is about 0.3 nm in terms of half full width (FWHM). Thus, the band width is not sufficiently narrow.

[0005] This problem may be solved by using a band narrowing unit for narrowing the band width of laser light. However, use of a band narrowing unit raises another problem that the exposure apparatus has to be operated fixedly with exposure light of a narrow spectrum. Thus, the latitude of the exposure apparatus with respect to the exposure light is limited considerably.

SUMMARY OF THE INVENTION

[0006] It is an object of the present invention to provide an exposure apparatus having a large latitude with respect to exposure light.

[0007] In accordance with an aspect of the present invention, there is provided an exposure apparatus having means for changing the band width of laser light. Particularly, the apparatus is provided with dispersing means for dispersing laser light with respect to wavelength, an optical system for collecting each of laser lights of wavelength units being dispersed and wavelength selecting means for changing the band width of laser light to be provided thereby, by changing a blocking portion for intercepting the collected laser light. With this arrangement, the spectrum of exposure light is made variable, and thus the latitude of the apparatus with respect to the exposure light is enlarged. This assures optimum exposure processes best suited to different types of wafer processes, respectively.

[0008] The dispersing element, the optical system and the wavelength selecting means may be provided within a resonator and, in that occasion, a decrease of intensity of the laser light is avoided irrespective of the provision of the band narrowing unit.

[0009] A Brewster window for transforming laser light into linearly polarized light as well as a reflector for turning the laser light back into a chamber may be provided within the resonator.

[0010] The dispersing element may comprise a prism or a diffraction grating. The laser may comprise an excimer laser.

[0011] One preferred form of the present invention comprises a first unit for making the spectral width of laser light smaller than a natural emission spectrum, and a second unit for setting the spectral width of the laser light at the natural emission spectrum, the first and second units being able to be used alternately, such that a larger latitude with respect to exposure light is assured.

[0012] In one preferred form of the present invention, the wavelength selecting means may comprise a slit of a variable opening width.

[0013] In one preferred form of the present invention, the second unit for setting the spectral width of laser light at the natural emission spectrum may comprise a total reflection mirror which may be interposed between the chamber of the resonator and the pair of the dispersing means and the wavelength selecting means.

[0014] In accordance with this aspect of the present invention, there is provided a high-resolution scan type exposure apparatus for scanning a mask and a substrate with laser light from a wavelength selecting means to thereby project a pattern of the mask onto the substrate.

[0015] In accordance with another aspect of the present invention, there is provided an exposure apparatus which comprises a first dispersing element for dispersing substantially parallel laser light, from a laser, with respect to wavelength to provide lights of wavelength units, a first optical system for collecting each laser light of a wavelength unit from the first dispersing element, wavelength selecting means for passing a desired wavelength region of laser light, of the lights of wavelength units each being collected by the first optical system, a second optical system for receiving the laser light from the wavelength selecting means and providing parallel lights of wavelength units, and a second dispersing element for combining the parallel laser lights of wavelength units from the second optical system, the second dispersing element having substantially the same angular dispersion as of the first dispersing element but having a direction of dispersion opposite to that of the first dispersing element. The dispersing elements may be disposed out of a resonator of the laser, to narrow the band width of the laser light, such that the emission strength of laser light is stable.

[0016] Also, the provision of the second optical system and the second dispersing element is effective to avoid or reduce eccentricity of wavelength distribution along the section of the laser light.

[0017] The wavelength selecting means may change the size of the region through which the laser light can pass, such that supply of laser light of a desired band width best suited to a wafer processes is allowed. For example, the wavelength selecting means may comprise slit means of variable slit width.

[0018] Each of the first and second dispersing element may comprise a prism or a diffraction grating. The laser may comprise an excimer laser.

[0019] In accordance with this aspect of the present invention, there is provided a high resolution scan type exposure apparatus for scanning a mask and a substrate with laser light from the second dispersing element by which a pattern of the mask is projected onto the substrate.

[0020] Also, in accordance with another aspect of the present invention, there is provided a device manufacturing method by which manufacture of devices of a large area and a high integration is allowed.

[0021] These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 is a schematic illustration of a first embodiment of the present invention.

[0023]FIG. 2 is a schematic illustration of the structure of a laser 1 of FIG. 1.

[0024]FIG. 3 is a schematic illustration of a modified form of the structure of the laser 1 of FIG. 1.

[0025]FIG. 4 is a schematic illustration of another modified form of the structure of the laser 1 of FIG. 1.

[0026]FIG. 5 is a schematic illustration of a second embodiment of the present invention.

[0027]FIG. 6 is a schematic illustration of a third embodiment of the present invention.

[0028]FIG. 7 is a schematic illustration of a fourth embodiment of the present invention.

[0029]FIG. 8 is a flow chart of device manufacturing processes.

[0030]FIG. 9 is a flow chart of a wafer process.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031]FIG. 1 shows a first embodiment of the present invention, and illustrates a scan type reduction projection exposure apparatus for use in manufacture of devices such as ICs, LSIs, CCDs, liquid crystal panels or magnetic heads, for example.

[0032] In FIG. 1, denoted at 1 is a KrF excimer laser which is a pulse laser light source for emitting pulsed laser light. This light source 1 emits light of wavelength of about 248 nm in deep ultraviolet region.

[0033] In FIG. 1, denoted at 2 is pulse light emitted by the light source 1, and denoted at 3 is a guiding optical system. Denoted at 4 is an illumination optical system, and denoted at 5 is a mask stage on which a mask having a device pattern to be transferred is placed. Denoted at 6 is a projection optical system for projecting the pattern of the mask onto a wafer 8. Denoted at 7 is a wafer stage on which a wafer 8 is placed. Denoted at 9 is a controller for controlling and setting conditions (process conditions) of exposure light to be projected to the wafer. Denoted at 10 is a laser controller for controlling the laser 1 in accordance with the conditions set by the controller 9. The mask stage 5 and the wafer stage 7 are scanned in the directions of arrows, relative to the illumination optical system 4 and the projection optical system 6, by which the scan exposure of the wafer 8 is performed.

[0034] For the condition setting, an operator specifies the pulse energy of the pulse light 2 and the number of pulses, to be determined by the required resolution and the resist sensitivity, for example, and inputs the data into the controller 9. In accordance with the specified conditions, the controller 9 determines the optimum or necessary laser emission conditions which may include the energy of each laser pulse, the emission frequency and the spectral width, for example.

[0035]FIG. 2 is a schematic view for explaining how to change the spectral width of the laser and the energy of each pulse in accordance with the determined emission conditions, and it shows details of the structure of the laser 1.

[0036] In FIG. 2, denoted at 11 is a laser chamber for the laser 1, and denoted at 2 is pulsed laser light. Denoted at 13 a and 13 b are prisms as dispersing elements, and denoted at 14 is a convex lens. Denoted at 15 is a variable slit having a variable width opening, being disposed at a focal point position of the convex lens 14. Denoted at 16 is a total reflection mirror disposed in close proximity to the variable slit 15, and denoted at 17 is a slit width adjusting device for actuating the variable slit 15 to change the width of the opening thereof. Denoted at 18 is a Brewster window for establishing a predetermined state of polarization in the laser light, and denoted at 19 is an output mirror for extracting a portion of the laser light out of the resonator. Denoted at 20 is a photodetector for detecting the energy (output) of the laser light to be directed to the guiding optical system 3.

[0037] In the exposure apparatus of this embodiment, the following adjustment may be done to obtain pulse laser light 2 of spectral width of about 0.1 nm, for example:

[0038] Where a KrF excimer laser is used, the laser chamber 11 emits laser light of basic emission band width of about 0.3 nm. The laser light emitted by the laser chamber 11 is dispersed with respect to wavelength by the prisms 13 a and 13 b.

[0039] The angular dispersion at respective surfaces of the prisms 13 a and 13 b is given by the following equation:

dθ/dλ=(dθ/dn)(dn/dλ)

[0040] where λ is the wavelength of the laser light, θ is the incidence angle and n is the refractive index of the prism 13 a or 13 b with respect to light of wavelength λ

[0041] If the prisms 13 a and 13 b are made of a glass material of synthetic quartz, the excimer laser comprises a KrF excimer laser, and the top or apex angle of the prism is 82 deg., and if the prisms are used with smallest deflection angle, then:

λ=248 nm

n=1.5084

dn/dλ=−5.610−4/nm

dθ/dn=(1/n) tan θ=4.56 rad

Thus,

dθ/dλ=−2.55 mrad/nm

[0042] Where two prisms are used for the dispersion as in the present embodiment, there are four refracting surfaces. Thus, if the focal length of the convex lens 14 is denoted by f and the width of the opening of the slit 15 is denoted by L, then the band width Δλ passing through the slit 15 is:

Δλ=L(f4dθ/dλ)

[0043] Therefore, the width L of the opening of the slit 15 may be set as follows to obtain light of a band width Δλ:

L=f4dθ/dλΔλ

[0044] For example, if the focal length of the convex lens is f=100 mm, then, in order to obtain a band width of 0.1 nm of the laser light after passing the slit 15, the width L of the opening of the slit 15 may be adjusted by the slit width adjusting device 17 to about 0.10 mm.

[0045] On the other hand, if a band width of about 0.3 nm of the laser light passing the slit 15 is desired, the slit width adjusting device 17 may be used to provide the opening width L of the slit 15 of not smaller than 0.30 mm.

[0046] The energy of each pulse of the laser light 2 can be changed by changing the width of the opening of the slit 15. As an example, if a spectral width of about 0.3 nm is desired and if a laser chamber 11 which supplies an emission energy of 20 mJ per each pulse is used, the pulse energy can be changed within a range of about 10 to 20 mJ by changing the slit width.

[0047] Therefore, if a higher resolution is required, the width of the opening of the slit 15 may be narrowed to provide a narrower spectral width of about 0.1 nm, for example. If on the other hand a higher throughput is desired and a larger output of the laser 1 is desired, the width of the opening of the slit 15 may be enlarged to provide a broader spectral band width of about 0.3 nm. In this adjustment, the photodetector 20 may be used to control the laser output to a desired level.

[0048] The center wavelength if the band width is narrowed depends on the central position of the slit 15. In consideration thereof, a wavelength detector may preferably be provided within (or out of) the photodetector 20 so as to allow that the position and width of the slit may be adjusted while monitoring the wavelength of the pulse laser light. Also, if it is desired to make stable the center wavelength of the pulse laser light, the output of the wavelength detector may be used to control the slit 15.

[0049] In the exposure apparatus of this embodiment, there are provided dispersing means (prism) for dispersing the laser light with respect to wavelength, and a lens for collecting or converging each laser light of a wavelength unit being dispersed, as well as wavelength selecting means (variable slit) for changing the band width of laser light to be provided thereby, by changing the portion for blocking the collected laser light, and they are disposed within a resonator. However, these components may be disposed outside the resonator.

[0050]FIG. 3 illustrate another example of changing the spectral width of the laser 1 and the energy of each pulse in accordance with the determined emission conditions, and it shows details of the structure of the laser 1.

[0051] In FIG. 3, denoted at 11 is a laser chamber for the laser 1, and denoted at 2 is pulsed laser light emitted from the laser 1. Denoted at 21 is a grating (diffraction grating) as a dispersing element, and denoted at 14 is a convex lens. Denoted at 15 is a variable slit having a variable width opening, being disposed at a focal point position of the convex lens 14. Denoted at 16 is a total reflection mirror disposed in close proximity to the variable slit 15, and denoted at 17 is a slit width adjusting device for actuating the variable slit 15 to change the width of the opening thereof. Denoted at 18 is a Brewster window for establishing a predetermined state of polarization in the laser light, and denoted at 19 is an output mirror for extracting a portion of the laser light out of the resonator. Denoted at 20 is a photodetector for detecting the energy (output) of the laser light to be directed to the guiding optical system 3.

[0052] Also in this embodiment, if the focal length of the convex lens is f=100 mm, then, in order to obtain a band width of 0.1 nm of the laser light after passing the slit 15, the width L of the opening of the slit 15 may be adjusted by the slit width adjusting device 17 to about 0.10 mm.

[0053] On the other hand, if a band width of about 0.3 nm of the laser light passing the slit 15 is desired, the slit width adjusting device 17 may be used to provide the opening width L of the slit 15 of not smaller than 0.30 mm.

[0054] The energy of each pulse of the laser light 2 can be changed by changing the width of the opening of the slit 15. As an example, if a spectral width of about 0.3 nm is desired and if a laser chamber 11 which supplies an emission energy of 20 mJ per each pulse is used, the pulse energy can be changed within a range of about 10 to 20 mJ by changing the slit width.

[0055] Therefore, if a higher resolution is required, the width of the opening of the slit 15 may be narrowed to provide a narrower spectral width of about 0.1 nm, for example. If on the other hand a higher throughput is desired and a larger output of the laser 1 is desired, the width of the opening of the slit 15 may be enlarged to provide a broader spectral band width of about 0.3 nm. In this adjustment, the photodetector 20 may be used to control the laser output to a desired level.

[0056] The center wavelength if the band width is narrowed depends on the central position of the slit 15. In consideration thereof, a wavelength detector may preferably be provided within (or out of) the photodetector 20 so as to allow that the position and width of the slit may be adjusted while monitoring the wavelength of the pulse laser light. Also, if it is desired to make stable the center wavelength of the pulse laser light, the output of the wavelength detector may be used to control the slit 15.

[0057] In the exposure apparatus of this embodiment, there are provided dispersing means (grating) for dispersing the laser light with respect to wavelength and a lens for collecting or converging each laser light of a wavelength unit being dispersed, as well as wavelength selecting means (variable slit) for changing the band width of laser light to be provided thereby, by changing the portion for blocking the collected laser light, and they are provided within a resonator. However, these components may be disposed outside the resonator.

[0058]FIG. 4 illustrate a further example of changing the spectral width of the laser 1 and the energy of each pulse in accordance with the determined emission conditions, and it shows details of the structure of the laser 1.

[0059] In FIG. 4, denoted at 11 is a laser chamber for the laser 1, and denoted at 2 is pulsed laser light. Denoted at 13 a and 13 b are prisms as dispersing elements, and denoted at 14 is a convex lens. Denoted at 15 is a variable slit having a variable width opening, being disposed at a focal point position of the convex lens 14. Denoted at 16 is a total reflection mirror disposed in close proximity to the variable slit 15, and denoted at 17 is a slit width adjusting device for actuating the variable slit 15 to change the width of the opening thereof. Denoted at 18 is a Brewster window for establishing a predetermined state of polarization in the laser light, and denoted at 19 is an output mirror for extracting a portion of the laser light out of the resonator. Denoted at 20 is a photodetector for detecting the energy (output) of the laser light to be directed to the guiding optical system 3. Denoted at 22 is a total reflection mirror which cooperates with the output mirror 19 to provide a natural emission (non-band narrowing) laser resonator. Denoted at 25 is a total reflection mirror drive controller for moving the total reflection mirror 22 out of and back into the light path.

[0060] In this embodiment, in order to narrow the band width of the laser light to less than 0.3 nm, the mirror drive controller 25 may be used to move the total reflection mirror 21 out of the light path. On the other hand, to provide a band width of about 0.3nm, the mirror drive controller 25 may be used to move the total reflection mirror 21 into the light path. In this manner, the resonator means can be interchanged between a first unit with which the spectral width of the laser light can be made smaller than that of natural emission spectrum and a second unit with which the spectral width of the laser light can be set at the natural emission spectrum. This assures an optimum laser emission condition adjusted to and best suited to a process condition.

[0061]FIG. 5 shows another embodiment of the present invention, and illustrates a scan type reduction projection exposure apparatus for use in manufacture of devices such as ICs, LSIs, CCDs, liquid crystal panels or magnetic heads, for example.

[0062] In FIG. 5, denoted at 101 is a laser (light source). Denoted at 102 is laser light emitted by the laser 1, and it is substantially parallel light. Denoted at 103 a and 103 b are prisms (dispersing elements) for dispersing the laser light with respect to wavelength. Denoted at 104 is a first convex lens for collecting or converging each of the laser lights of wavelength units, being dispersed by the prisms 103 a and 103 b. Denoted at 105 is a variable slit having a variable width region (opening) for passing light. It is disposed at the focal point position of the first convex lens 104. Denoted at 106 is a second convex lens disposed separately from the variable slit 105, at a distance corresponding to the focal length thereof. Denoted at 107 a and 107 b are prisms having the same angular dispersion as of the prism 103 a or 103 b. Denoted at 108 is an illumination optical system, and denoted at 109 is a mask having a device pattern to be transferred to a wafer. Denoted at 110 is a projection optical system for projecting the pattern of the mask onto the wafer. Denoted at 111 is a wafer on to which the device pattern of the mask 109 is to be transferred. Denoted at 112 is a slit width adjusting device for actuating the variable slit 105 to change the width of the opening thereof. The mask 109 and the wafer 111 are scanned in the directions of arrows, relative to the laser light and the optical system 110.

[0063] In the exposure apparatus of this embodiment, the width of the opening of the variable slit 105 is so adjusted to supply only laser light of a band width of 0.1 nm to the illumination optical system 108, and the dispersing means is provided outside the resonator of the laser 101 to narrow the band width of the laser light 2. Thus, the emission strength of the laser light 2 is quite stable.

[0064] If a KrF excimer laser is used as the laser 101, the laser 101 emits laser light 102 of a band width of 0.3 nm. This laser light 102 is dispersed by the dispersing means of the prisms 103 a and 103 b and, by means of the convex lens, each laser light of the same wavelength is collected or converged onto the variable slit 105.

[0065] The angular dispersion at respective surfaces of the prisms 103 a and 103 b is given by the following equation:

dθ/dλ=(dθ/dn)(dn/dλ)

[0066] where λ is the wavelength of the laser light 102, θ is the incidence angle and n is the refractive index of the prism 103 a or 103 b with respect to light of wavelength λ.

[0067] If the prisms are made of a glass material of synthetic quartz, the excimer laser 101 comprises a KrF excimer laser, and the top or apex angle of the prism is 82 deg., and if the prisms are used with smallest deflection angle, then:

λ=248 nm

n=1.5084

dn/dλ=−5.6104/nm

dθ/dn=(1/n) tan ↓=4.56 rad

[0068] Thus,

dθ/dλ=−2.55 mrad/nm

[0069] Where two prisms are used for the dispersion as in the present embodiment, there are four refracting surfaces. Thus, if the focal length of the convex lens 104 is denoted by f and the width of the opening of the slit 105 is denoted by L, then the band width Δλ passing through the slit 105 is:

Δλ=L(f4dθ/dλ)

[0070] Therefore, the width L of the opening of the slit 105 may be set as follows to obtain light of a band width Δλ:

L=f4dθ/dλΔλ  (2)

[0071] For example, if f=100 mm, then, in order to obtain a band width of 0.1 nm of the laser light after passing the slit 105, the width L may be set to be equal to 0.10 mm.

[0072] On the other hand, if a band width of about 0.3 nm of the laser light passing the slit 105 is desired, the slit width adjusting device 112 may be used to provide the opening width L of the slit 105 of not smaller than 0.30 mm.

[0073] The strength of the laser light 102 directed to the illumination optical system 108 can be changed by changing the width of the opening of the slit 105. Therefore, if a higher resolution is required, the width of the opening of the slit may be narrowed to provide a narrower spectral width of about 0.1 nm, for example. If on the other hand a higher throughput is desired and supply of stronger light to the illumination optical system 108 is desired, the opening of the slit may be enlarged.

[0074] The laser light 102 after passing the slit 105 has eccentricity of wavelength in dependence upon the advancement direction. However, this eccentricity of wavelength is canceled in the exposure apparatus of the present embodiment by transforming the laser light back to parallel light by means of the convex lens 106 and the prisms 107 a and 107 b, of the same shapes as the convex lens 104 and the prisms 103 a and 103 b and disposed symmetrically with respect to the slit 105 and by simultaneously applying dispersion opposite to the dispersion applied by the prisms 103 a and 103 b. Thus, the eccentricity canceled laser light is supplied to the illumination optical system 108.

[0075] The laser light 102 is then shaped by the illumination optical system 108 to have a predetermined N.A. (numerical aperture) and a predetermined illuminance distribution, and subsequently it is projected on the mask 109. After passing the mask 109, it goes through the projection optical system 110 which is provided to project the device pattern of the mask 109 onto the wafer 111 in a reduced scale, such that the wafer 111 is exposed with the projected light.

[0076] In order to change the wave band width Δλ of the exposure light, the slit width adjusting device 112 is actuated to adjust the slit width L of the variable slit 105 in accordance with equation (1).

[0077]FIG. 6 is a schematic view of a further embodiment of the present invention, and it shows a scan type reduction projection exposure apparatus for use in manufacture of devices such as ICs, LSIs, CCDs, liquid crystal panels or magnetic heads, for example. In FIG. 6, the same reference numerals as of FIG. 5 are assigned to corresponding elements.

[0078] The exposure apparatus of FIG. 6 is distinguished from the exposure apparatus of FIG. 5 in the provision of a member 113. This member 113 is used when, upon dispersing the laser light by a prism to produce light of a desired wavelength width Δλ, the diversion angle of the laser light 2 is so large as can not be disregarded.

[0079] The element 113 comprises a beam expander which serves to expand the laser light 2, emitted by the laser 1, and which also serves to reduce the diversion angle. By means of this beam expander 113, the expansion rate of the laser beam diameter is changed in accordance with the dispersion angle Δθ by the prism and the diversion angle of the laser light 102. By this, exposure light of wavelength width Δλ is correctly produced.

[0080]FIG. 7 is a schematic view of a further embodiment of the present invention, and it shows a scan type reduction projection exposure apparatus for use in manufacture of devices such as ICs, LSIs, CCDs, liquid crystal panels or magnetic heads, for example. In FIG. 7, the same reference numerals as of FIG. 5 are assigned to corresponding elements.

[0081] The exposure apparatus of FIG. 7 is distinguished from the exposure apparatus of FIG. 5 in the use of gratings (diffraction gratings) in place of prisms, as the dispersing means. In FIG. 7, denoted at 113 and 114 are gratings which serve as dispersing elements. The grating 113 is provided in place of the prisms 3 a and 3 b of FIG. 1, and the grating 114 is provided in place of the prisms 7 a and 7 b of FIG. 1. Generally, a grating has a larger angular dispersion as compared with a prism, and the exposure apparatus of FIG. 7 has an advantage in a case where a narrower band width exposure light is desired.

[0082] Next, an embodiment of device manufacturing method which uses one of the exposure apparatus of FIGS. 1-7, will now be explained.

[0083]FIG. 8 is a flow chart of the sequence of manufacturing a semiconductor device such as a semiconductor chip (e.g. IC or LSI), a liquid crystal panel or a CCD, for example. Step 1 is a design process for designing the circuit of a semiconductor device. Step 2 is a process for manufacturing a mask on the basis of the circuit pattern design. Step 3 is a process for manufacturing a wafer by using a material such as silicon.

[0084] Step 4 is a wafer process which is called a pre-process wherein, by using the so prepared mask and wafer, circuits are practically formed on the wafer through lithography. Step 5 subsequent to this is an assembling step which is called a post-process wherein the wafer processed by step 4 is formed into semiconductor chips. This step includes assembling (dicing and bonding) and packaging (chip sealing). Step 6 is an inspection step wherein operability check, durability check and so on of the semiconductor devices produced by step 5 are carried out. With these processes, semiconductor devices are finished and they are shipped (step 7).

[0085]FIG. 9 is a flow chart showing details of the wafer process. Step 11 is an oxidation process for oxidizing the surface of a wafer. Step 12 is a CVD process for forming an insulating film on the wafer surface. Step 13 is an electrode forming process for forming electrodes on the wafer by vapor deposition. Step 14 is an ion implanting process for implanting ions to the wafer. Step 15 is a resist process for applying a resist (photosensitive material) to the wafer. Step 16 is an exposure process for printing, by exposure, the circuit pattern of the mask on the wafer through the exposure apparatus described above. Step 17 is a developing process for developing the exposed wafer. Step 18 is an etching process for removing portions other than the developed resist image. Step 19 is a resist separation process for separating the resist material remaining on the wafer after being subjected to the etching process. By repeating these processes, circuit patterns are superposedly formed on the wafer.

[0086] While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims.

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US7812283 *Mar 24, 2005Oct 12, 2010Semiconductor Energy Laboratory Co., Ltd.Laser irradiation method, laser irradiation apparatus, and method for fabricating semiconductor device
US8304313Aug 12, 2005Nov 6, 2012Semiconductor Energy Laboratory Co., Ltd.Semiconductor device and its manufacturing method
US8395084Apr 26, 2006Mar 12, 2013Semiconductor Energy Laboratory Co., Ltd.Laser irradiation apparatus and laser irradiation method
US8525075 *May 4, 2005Sep 3, 2013Semiconductor Energy Laboratory Co., Ltd.Laser irradiation apparatus
Classifications
U.S. Classification359/615
International ClassificationG03F7/20, H01S3/225, H01S3/13, H01S3/134
Cooperative ClassificationH01S3/134, H01S3/1305, H01S3/225, G03F7/70091
European ClassificationG03F7/70D8, H01S3/225
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