WO1991003075A1

WO1991003075A1 - Gas substrate processing module

Info

Publication number: WO1991003075A1
Application number: PCT/US1990/004746
Authority: WO
Inventors: Sherman U. Moxness; Robert W. Grant
Original assignee: Fsi International, Inc.
Priority date: 1989-08-21
Filing date: 1990-08-21
Publication date: 1991-03-07

Abstract

A reactive gas processing chamber for wafer substrates (16) of the type to be used in the manufacture of IC chips. The cover (12) may be provided with an ultraviolet light source (18) to irradiate the wafer (16) and reactive gases through a UV transparent window (20). The base (14) provides a specific gas flow pattern of the reactive process gases over the exposed surface of the wafer (16) to maximize contact of the gas with the wafer (16), and efficiency and completeness of the processing procedure.

Description

GAS SUBSTRATE PROCESSING MODULE Field of the Invention. This invention relates to a reactive gas processing apparatus with a minimally sized substrate chamber for cleaning and processing of a single substrate, such as a wafer used in IC chip manufacture. The substrate-containing chamber is closely sized to the substrate dimensions to provide precise control of processing conditions and also minimal gas usage for effective processing. The reactive gases may be any known cleaning and/or processing gases. In a particular embodiment, the reactive gas is ozone generated in situ by UV irradiation of oxygen, in which embodiment the apparatus of the present invention is provided with a separate UV lamp containing chamber to irradiate the oxygen gas and the substrate surface.

Background of the Invention Examples of reactive gas processes used in cleaning or etching wafers are found interalia in U.S. Patent Nos. 4,025,135 and 4,749,440. Those patents describe processing apparatus which are fairly large compared to the size of the substrate wafer, requiring larger amounts of processing gases and preventing precise control of reaction parameters.

Summary of the Invention The processing and cleaning apparatus of this invention thus uses a substrate confining chamber minimally sized to the substrate dimensions. The reactive gas flow enters the substrate chamber through a diffusing manifold baffle at one side of and behind the exposed substrate surface, flows across the substrate surface in close proximity thereto because of the minimal substrate chamber dimensions, and exits the substrate chamber at the other side of and behind the substrate. The gas entrance and exit means may each be a porous membrane, a slit or an array of perforations parallel with and equal to the substrate diameter. A constriction between the edge of the substrate supporting bed and the substrate chamber cover further provides a gas diffusing nozzle to uniformly spread the reactive gas over the wafer face. The substrate supporting bed may be slightly tilted toward the gas entrance or exit means to provide further control of the gas flow path over the substrate surface. _. As previously stated, any conventional reactive process gases for processing substrates may be used in the present apparatus. Anhydrous reactive gas in the presence of water vapor, such as described in U.S. Patent No. 4,749,440, may be used. Also, the reactive gas used may be ozone generated in situ from UV irradiation of oxygen, as described in U.S. Patent No. 4,028,155 and in John R. Vig, J. Vac. Sci. Techno1.. Vol. A3, No. 3, May-June 1985, pages 1027-1034. To use the UV/ozone reactive gas, the present module is modified to have a UV lamp positioned in the cover above the wafer surface in a gas tight, lamp chamber separate from the substrate chamber. Brief Description of the Drawings

Figure 1 is an exploded view of an apparatus of the present invention containing a UV light source chamber behind a UV transparent window in the cover, with parts separated to show the construction of the cover and base.

Figure 2 is a top plan view of the apparatus of Figure 1 with broken lines to show the position of the integral parts of the cover and base.

Figure 3 is a profile taken along the line 3-3 in Figure 2 showing the cover and base with a UV light source chamber within the cover and the substrate chamber between the cover and the base. Figure 4 is a profile similar to that of Figure 3 with a solid cover not containing the UV light source.

Figure 5 is a profile similar to that of Figure 4 with the substrate supporting means inclining the surface of the substrate toward the gas introducing means. ___. Detailed Description of the Invention

Figure 1 is an exploded view of an apparatus 10 of the present invention with parts separated to show the construction of the cover 12 and base 14 and containing a wafer substrate 16. The wafer substrate 16 is illustrated as having arcs cut off therefrom, but may also be a full circle wafer. The assembled cover 12 and base 14 form the substrate chamber. The apparatus 10, as illustrated in Figure 1, contains a UV light source 18 behind a UV transparent window 20, for use with the oxygen-ozone reactive process gas system. The UV light source for use in this invention is a low pressure mercury vapor lamp. A suitable UV lamp has been found to be a UV radiation and ozone generation grid lamp 88-9102-02 from BHK, Inc., Monrovia, CA. As shown in Figure 1, the UV lamp 18 is formed with a polished aluminum reflector 22 to ensure that all UV light is directed down to the wafer surface 16. The UV transparent window may be UV transparent sapphire or fused silica. A suitable fused silica is Grade OA available from Corning Glass Advanced Products Div. The cover 12 is constructed with a back plate 24 formed with a recess 26 to accommodate the UV light source 18. Apertures 28 in the back plate 24 are provided for connection of the UV light source 18 to an external power source, not shown. A first spacer 30, formed with an opening 32 sized to permit UV light to be directed across the entire exposed surface of the wafer substrate 16, is interposed between the UV light source 18 and the UV transparent window 20. The lower face of first spacer 30 is provided a vapor tight gasket 34 around the perimeter to confront the UV transparent window 20 and form a vapor tight seal therewith. A second spacer 36, also formed with an opening 38 sized to permit UV light to be directed across the entire exposed surface of the wafer substrate 16, is interposed between the UV transparent window 20 and the face plate 40 of the cover 12. The recess 42 in the second spacer 36 is formed to retainingly support the raised interior perimeter 44 of the back plate 24, the UV light source 18, the first spacer 30 and the UV transparent window 20 therein. The second spacer 36 is also provided with a vapor tight gasket 46 to provide a vapor tight seal with the back plate 24 around the raised interior perimeter 44. The face plate 40 is formed with an opening 48 sized to permit UV light to be directed across the entire exposed surface of the wafer substrate 16, a recess 50 to retainingly support the raised central perimeter 52 of the back plate 24, the UV light source 18, the first spacer 30, the UV transparent window 20 and the second spacer 36 therein. The face plate 40 is provided with a vapor tight gasket 54 to provide a vapor tight seal with the back plate 24 around the raised central perimeter 52. All the aforementioned pieces of the cover 12 interfit together in sandwich-fashion and are held together in vapor tight alignment by - threaded screws 55. Thus the cover 12 as just described forms a vapor tight chamber for the UV lamp 18, separate from the substrate containing chamber, to be described further hereinbelow. The base 14 of the chamber 10 of the present invention, as illustrated in Figure 1, is provided with a raised bed 56 formed with a recess 58 to support the wafer substrate with its surface exposed to reactive process gas and to.the UV light, when present in the cover 12. A wafer access channel 60 is formed in the raised bed 56 to provide access to position and remove the wafer substrate 16. Gas inlet 62 and outlet 64 are positioned behind the exposed surface of the substrate wafer 16 and on either side thereof. A pair of parallel lines of holes 66, 68 in gas flow communication with the gas inlet 62 and outlet 64, respectively, are positioned behind the exposed surface of the substrate wafer 16, on either side thereof, and equal in length to the diameter of the substrate wafer 16. The raised bed 56 and the gas lines of holes 66, 68 are positioned and sized to fit within the recess 48 of the face plate 40. When the base 14 and cover 12 are assembled together with the substrate wafer 16, gas tight flow communication allows introduced gas to flow through inlet 62 and line of holes 66 over the wafer 16 surface and out through outlet 64 and line of holes. The purpose of the pair of parallel lines of holes 66, 68 is to each form a baffle manifold to ensure uniform distribution of the process gas over the wafer surface. Alternatively, these baffle manifolds may be a pair of slits parallel with and having a length equal to the substrate diameter, or may be gas porous media, such as gas porous PVDF or Teflon®, available from Porex, Atlanta, GA or Millipore, Bedford, MA. Additionally, the gas inlet 62 and outlet 64 may, instead of being each a single port, also each be a baffle manifold to further enhance uniform gas distribution. It is important to proper cleaning of the wafer substrate surface to insure that the path of travel over the wafer is as uniform as possible. It is thus also important that, where the gas travels over the_.full diameter of the wafer, more gas is available for surface treatment, than where the gas travels over only the edges of the wafer. Thus, the gas introducing and exit means can be formed to supply more gas to the wafer middle, as by making the gas slits or gas holes slightly larger in that area. In addition, as shown in Figures 3, 4 and 5, a constriction 83, 85, 87, respectively formed between the raised wafer supporting bed 56, 89, 96, respectively, and the adjacent spacer 36, 78 respectively provides a nozzle effect to further ensure uniform distribution of the gas over the wafer surface.

The interior of the substrate chamber and its constituent parts are constructed and designed to ensure that the path of travel of the reactive gas is uniformly distributed and is maintained in close proximity to the exposed surface of the substrate wafer 16. Thus, the substrate chamber is dimensioned for minimal non-contact with the substrate. Thus, the window 20 should have a minimum clearance from the substrate surface of about 0.050 inch, preferably about 0.125 inch from the substrate surface to a maximum clearance of about two times the wafer thickness. As shown in the accompanying Figures, the substrate chamber may be generally rectangular, having a length from the gas introducing means to the gas exit means across the wafer surface and a width at right angles to the length across the wafer surface. The length will generally be about 1.25 times the wafer diameter or about 2 inches or less on either side of the wafer, for 4-8 inch diameter wafers. The width will generally be about 1.05 times the wafer diameter or between about 3/32 inch to l^*ess than one inch on either side of the wafer, for 4-8 inch diameter wafers. Since it is important to have the chamber be as small as possible to maintain an even flow pattern, the dimensions of the substrate chamber are sized to ^"specific wafer dimensions.

Figure 2 is a top plan view of the apparatus 10 of Figure 1 with broken lines to show the position of the integral parts of the cover 12 and base 14 assembled in gas tight flow communication. Figure 3 is a profile of the chamber 10 taken along the line 3-3 in Figure 2 showing the cover 12 and base 14 with a UV light source 18 within the cover 12.

Figure 4 is a profile of an alternate apparatus 72 according to the present invention similar to that of Figure 3, but with a cover 74 omitting the UV light source. The cover 74 is formed with the back plate 76, spacer 78, window 80 and face plate 82. Back plate 76 is similar to back plate 24, with the omission of apertures 28 for UV light power source. Spacer 78 is similar to second spacer 36, with its dimensions sized to accommodate for the absence of the UV light source 18, the first spacer 30 and the UV transparent window 20. Window 80 is similar to UV transparent window 20, except that it need not be of UV transparent material. Face plate 82 is similar to face plate 40. The apparatus 72 as illustrated in Figure 4 has the same base 14 as illustrated and described with reference to Figures 1 and 2.

Figure 5 is a profile of another alternate chamber 84 according to the present invention similar to that of Figure 4, illustrated as having the cover 74 as described in Figure 4 with an alternate base 86, wherein the substrate supporting means inclines the surface of the substrate 16 toward the gas inlet 88. Of course, this alternate base 86 may also be used with the UV light containing cover 12. Gas inlet 88 and outlet 90 are positioned behind the exposed surface of the substrate wafer 18 and on either side thereof, in the manner as previously described for base 14 with reference to Figures 1 - 4. A pair of parallel slits 92, 94 in gas flow communication with the gas inlet 88 and outlet 90, respectively, are positioned behind the exposed surface of the substrate wafer 16, on either side thereof, and equal in length to the diameter of the substrate wafer 16. The inclined raised bed 96 supports the substrate wafer within the wafer substrate recess 98, so that the exposed surface of the substrate 16 is inclined toward the gas inlet

88. The inclined raised bed 96 and the gas slits 92, 94 are positioned and sized to fit within the recess of the face plate 82. When the base 86 and cover 82 are assembled together with the substrate wafer 16 as illustrated in Figure 5, gas tight flow communication allows introduced gas to flow through gas inlet 88 and slit 92 over the wafer 16 surface and out through gas outlet 90 and slit 94. The materials of the apparatus are chosen to be inert to the reactive cleaning gases and to the UV light, when used.- They may suitably be formed of PVDF or an acid resistant base material coated with silicon carbide or silicon nitride.

Either cover 12 or 74 will interfit with either base 14 or 86. The inlet 66, 92 and outlet gas slits 68, 94 may alternatively each be a line of holes parallel with each other, respectively, and equal to the substrate diameter or a gas porous media. Detailed Description of the Method

When the inventive gas processing apparatus of the present invention is to be used in processing wafer substrates with oxygen/ozone processing gas, the method of the present invention is described as follows. The cover 12, as described herein above with reference to Figures 1, 2 and 3, is interfitted with either of the bases 14 or 86, as described herein above with reference to any of the figures, containing a substrate wafer 16. The cover 12 is maintained in gas tight sealed alignment with the base by any suitable means, such as by screw fitting the cover to the base or by exerting steady even pressure, as by a pneumatic press. The base may use either the parallel pair of gas slits or the pair of lines of holes parallel with each other, or a gas porous media as described herein above.

Oxygen gas is introduced into the chamber over the surface of the substrate. It is important that the oxygen be a pure oxygen source uncontaminated by impurities normally found in air, such as nitrogen, sulfur, or their oxides. In order to assist the cleaning effect of the ozone, the introduced oxygen may be enriched with up to 10% ozone. The ultraviolet lamp is activated to irradiate through the UV transparent window onto the substrate surface. The ultraviolet light contains both 185 nm and 254 nm frequency wavelengths. The 185 nm frequency ultraviolet light generates the oxygen into ozone to react with and vaporize organic contaminants on the substrate surface. The 254 nm frequency ultraviolet light then degenerates the ozone to oxygen, and the gases and reaction products are removed from the chamber through the exit means. Operation of the chamber with oxygen/ozone processing gas can be at temperatures of about 40° to 70° C. Slightly elevated temperatures have been found to maximize UV output, with 185 nm radiation maximizing at about 70°C and 254 nm radiation maximizing at about 40°-50°C. Providing a separate chamber for the UV lamp allows precise control of the UV lamp operating temperature to maximize the desired output frequency and also prolongs the life of the lamp by separating it from the process gas environment. In - li ¬

the apparatus of the Vig article referred to above and of U.S. Pat. No. 4,028,155, no separate lamp chamber is described or suggested. The time required for adequate cleaning of organic surface contaminants on the substrate wafer may vary from 10 sec. to about 5 min., depending on the identity and quantity of the contaminants. Thus, removal of photoresists of thicknesses of about 500 Angstroms or more would require the longer times, while minor surface atom contaminants could be removed in a few seconds. A heating element may be provided under the wafer support bed to heat the wafer to elevated temperatures as high as 250° C or even 600° to 700° C to increase the processing and decrease the time to a few seconds.

The UV light containing apparatus may also be used with other reactive gas processing mixtures, such as those containing ammonia or nitric acid.

When the inventive gas processing chamber of the present invention is to be used in processing wafer substrates with reactive processing gases which do not require UV light, the method of the present invention is described as follows. The alternate cover 74, as described herein above with reference to Figures 4 and 5, is interfitted with either of the bases 14 or 86, as described herein above with reference to any of the Figures, containing a substrate wafer in the substrate bed. Again, the cover 74 is maintained in gas tight sealed alignment with the base by any suitable means, as described herein above.

Reactive processing gas is introduced into the chamber to flow over the exposed surface of the substrate. The reactive processing gas may be anhydrous hydrogen fluoride in the presence of water vapor, according to the process described in U. S. Patent No. 4,749,440, which is hereby specifically incorporated by reference to describe the various necessary reaction parameters. Any other processing gas procedures as described therein or any other reactive gas processing procedures commonly used in processing wafer substrates to be used in the manufacture of IC chips may also be carried out in this chamber.

Claims

What Is Claimed Is:

1. A processing apparatus for applying reactive processing gas to a surface of a substrate, comprising: a gas-tight substrate chamber for supporting a substrate with the substrate surface exposed to reactive processing gas, said chamber dimensioned for minimal non-contact with the substrate; means for introducing gas into the chamber interior from below and on one edge of the substrate to flow uniformly across the substrate surface to a gas exit means positioned below the substrate on an edge opposite the introducing- means.

2. A processing apparatus according to claim 1, wherein the gas introducing and gas exit means are each provided with a gas manifold baffle to enhance uniform gas flow across the substrate surface.

3. A processing apparatus according to claim 1, wherein the substrate is a wafer to be used in the manufacture of integrated circuit chips.

4. A processing apparatus according to claim 1, wherein the substrate supporting means maintains the substrate surface inclined toward the gas introducing means.

5. A processing apparatus according to claim 1, wherein the substrate supporting means maintains the substrate surface inclined toward the gas exit means.

6. A processing apparatus according to claim 1, wherein the gas introducing means and the gas exit means are each slits parallel with and having a length equal to the substrate diameter, said slits being positioned below the substrate surface and at opposite edges of the substrate diameter.

7. A processing apparatus according to claim 1, wherein the gas introducing means and the gas exit means are each a line of holes, said line of holes each having a length essentially equal to the substrate diameter, each line of holes being positioned below the substrate surface and at opposite edges of the substrate diameter.

8. A processing apparatus according to claim 1, wherein the chamber comprises a base for supporting the substrate with its surface exposed to reactive gas and a cover for enclosing the substrate within the base in gas-tight sealing relationship and for maintaining the reactive gas flow in close proximity to the substrate surface, said-cover and base together dimensioned for minimal non-contact with the substrate surface.

9. A processing apparatus according to claim 8, wherein the cover is provided with a UV transparent window, said window and said cover together defining a separate gas-tight UV light source chamber supporting a UV light source for directing UV light through the window to the substrate surface.

10. A processing apparatus according to claim 9, wherein the ultraviolet light source generates both 185 nm and 254 nm wavelengths, the introduced gas is oxygen, the 185 nm wavelength UV light generates the oxygen into ozone to react with the substrate surface, the 254 nm wavelength ultraviolet light degenerates the ozone to oxygen, and gases and reaction products are removed from the chamber through the gas exit means.

11. A processing apparatus according to claim 10, wherein the window is quartz or sapphire.

12. A processing apparatus according to claim 10, wherein the oxygen is pure oxygen, optionally enriched with up to 10% ozone.

13. A processing apparatus according to claim 8, wherein the cover is a minimum clearance from the substrate surface of about 0.050 inch.

14. A method for reactive gas processing of a substrate comprising: supporting a substrate in a gas-tight substrate chamber with the substrate surface exposed to reactive processing gas, said chamber dimensioned for minimal non-contact with the substrate; introducing gas into the chamber interior through a gas introducing means positioned below and on one edge of the substrate to flow uniformly across the substrate surface to a gas exit means positioned below the substrate on an edge opposite the introducing means.

15. A reactive gas processing method according to claim 14, wherein the gas introducing and exit means are each provided with a gas manifold baffle to enhance uniform gas flow across the substrate surface.

16. A reactive gas processing method according to claim 14, wherein the substrate is a wafer to be used in the manufacture of integrated circuit chips.

17. A reactive gas processing method according to claim 14, wherein the substrate supporting means maintains the substrate surface inclined toward the gas introducing means.

18. A reactive gas processing method according to claim 14, wherein the substrate supporting means maintains the substrate surface inclined toward the gas exit means.

19. A reactive gas processing method according to claim 14, wherein the gas introducing means and the gas exit means are each slits parallel with and having a length equal to the substrate diameter, said slits being positioned below the substrate surface and at- opposite edges of the substrate diameter.

20. A reactive gas processing method according to claim 14, wherein the gas introducing means and the gas exit means are each a line of holes parallel with and having a length equal to the substrate diameter, said lines of holes being positioned below the substrate surface and at opposite edges of the substrate diameter.

21. A reactive gas processing method according to claim 14, wherein the chamber comprises a base for supporting the substrate with its surface exposed to reactive gas and a cover for enclosing the substrate within the base in gas-tight sealing relationship and for maintaining the reactive gas flow in close proximity to the substrate surface, said cover and base together dimensioned for minimal non-contact with the substrate surface.

22. A reactive gas processing method according to claim 21, wherein the cover is provided with a UV transparent window, said window and said cover - together defining a separate gas-tight UV light source chamber supporting a UV light source for directing UV light through the window to the substrate surface.

23. A reactive gas processing method according to claim 22, wherein the ultraviolet light source generates both 185 nm and 254 nm wavelengths, the introduced gas is oxygen, the 185 nm wavelength UV light generates the oxygen into ozone to react with the substrate surface, the 254 nm wavelength ultraviolet light degenerates the ozone to oxygen, and gases and reaction products are removed from the chamber through the gas exit means.

24. A reactive gas processing method according to claim 23, wherein the window is quartz or sapphire

25. A reactive gas processing method according to claim 23, wherein the oxygen is pure oxygen, optionally enriched with up to 10% ozone.

26. A reactive gas processing method according to claim 21, wherein the cover is a minimum clearance from the substrate surface of about 0.050 inch.

27. A processing apparatus according to claim 2, wherein the gas introducing and gas exit means are provided with a gas porous membrane to further enhance the uniformity of gas flow across the substrate surface.