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1. (WO1989000341) METHOD OF FABRICATING SOLAR CELLS WITH ANTI-REFLECTION COATING
Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters
-22-

WHAT IS CLAIMED IS:

1. Method of fabricating a solid state semiconductor device comprising:
(a) providing a silicon substrate having first and second opposite surfaces;
(b) forming a P/N junction in said substrate adjacent to said first surface;
(c) subjecting said first surface sequentially to (1) a plasma treatment long enough to produce hydrogen implantation and (2) a combined silane and ammonia plasma treatment long enough to produce additional hydrogen implantation and formation of a polysilazane coating;
(d) etching a predetermined two-dimensional pattern in said polysilazane coating so that selected portions of said first surface are not covered by said
polysilazane coating;
(e) applying a coating of aluminum to said second opposite surface;
(f) heating said silicon substrate to a temperature and for a time sufficient to cause the aluminum
constituent of said aluminum coating to alloy with said silicon substrate;
(g) applying a conductive metal coating to said selected portions of said first surface; and
(h) sintering said conductive metal coating so that the conductive metal and silicon react and bond at their interface.

SUBSTITUTE SHEET -23-

2. Method according to claim 1 wherein said
polysilazane coating has a refractive index of 2.15 after step (f) .

3. Method according to claim 1 wherein said
polysilazane coating has a thickness of between about 840 and 890 Angstroms.

4. Method according to claim 3 wherein said
polysilazane coating has a thickness of about 850
Angstroms.

5. Method according to claim 1 wherein said
polysilazane coating has a thickness of between about 840 and about 890 Angstroms and a refractive index of about 2.15.

6. Method according to claim 1 wherein said solid state semiconductor device is a photovoltaic cell.

7. Method of fabricating a solid state semiconductor device comprising:
(a) providing a silicon substrate having first and second opposite surfaces;
(b) forming a shallow P/N junction in said
substrate adjacent said first surface;
(c) subjecting said first surface to (1) an ammonia plasma so as to produce hydrogen implantation at said surface and (2) a combined silane and ammonia plasma so as to produce additional hydrogen implantation and formation of a polysilazane coating on said first

SUBSTITUTE SHEET -24- surface;
(d) covering said polysilazane coating with an adherent coating of a photoresist material;
(e) exposing said photoresist coating to radiant energy through a mask defining a predetermined
two-dimensional pattern;
(f) chemically developing said photoresist so that selected portions of said resist are removed from said polysilazane coating according to said predetermined pattern;
(g) removing those portions of said polysilazane coating which are not covered by said photoresist so that selected portions of said first surface are exposed to the atmosphere;
(h) applying a coating of aluminum to said second opposite surface;
(i) heating said silicon substrate to a temperature and for a time sufficient (1) to cause the aluminum constituent of said aluminum coating to alloy with said silicon substrate and (2) to drive the hydrogen
implanted in step (c) above substantially fully- through said substrate;
(j) applying a solderable metal coating to said selected portions of said first surface; and
(k) sintering said solderable metal coating so that the solderable metal and silicon react to form a solderable metal silicide at their interface.

8. Method according to claim 7 wherein the substrate is subjected to ammonia plasma at a temperature of between about 320 degrees C and about 500 degrees C for at least about 1.0 minute.

9. Method according to claim 7 wherein said substrate is subjected to ammonia plasma at a temperature of about 360 degrees C.

10. Method according to claim 7 wherein said
polysilazane coating is represented by the formula

Si H N , where x and z each range from about 1.0 to x y z
about 1.3 and y ranges from about .05 to about .30.

11. Method according to claim 7 wherein said substrate is exposed to ammonia plasma for at least about 1.0 minute and is exposed to said ammonia and silane plasma for at least about 2.8 minutes.

12. Method according to claim 7 wherein said
polysilazane coating has a thickness of between about 840 and about 890 Angstroms.

13. Method according to claim 7 wherein said
polysilazane coating has a refractive index of 2.15 after step (i) .

14. Method according to claim 7 wherein the aluminum alloying causes implanted hydrogen to be driven further into the bulk of the substrate.

15. Method of fabricating a solid state semiconductor device comprising:
(a) providing a silicon substrate having first and

SUBSTITUTE SHEET -26- second opposite surfaces;
(b) forming a P/N junction in said substrate adjacent said first surface;
(c) subjecting said first surface sequentially to (1) an ammonia plasma long enough to produce hydrogen implantation in said substrate, and (2) a combined silane and ammonia plasma long enough to produce additional hydrogen implantation and formation of a polysilazane coating;
(d) covering said polysilazane coating with an adherent coating of a photoresist material;
(e) exposing said photoresist coating to radiant energy through a mask defining a predetermined
two-dimensional pattern;
(f) chemically developing said photoresist so that selected portions of said resist are removed from said polysilazane coating according to said predetermined pattern ,- (g) removing those portions of said polysilazane coating which are not covered by said photoresist so that selected portions of said first surface are exposed to the atmosphere;
(h) applying a coating of aluminum to said second opposite surface;
(i) heating said silicon substrate to a temperature and for a time sufficient to (1) cause the aluminum constituent of said aluminum coating to alloy with said silicon substrate, (2) densify the polysilazane coating so that it is more nearly silicon nitride, and (3) drive the implanted hydrogen further into the
substrate;
SUBSTITUTE SHEET (j) applying a coating of a solderable conductive metal to said selected portions of said first surface; and
(k) sintering said conductive metal so that the conductive metal and silicon react to form a conductive metal silicide at their interface.

16. Method according to claim 15 further including the steps of contacting said layer of conductive metal with an etchant to remove unbonded conductive metal, and overcoating said layer of conductive metal with
additional conductive metal.

SUBSTITUTE SHEET AMENDED CLAIMS
[received by the International Bureau
on 7 November 1988 (07.11.88);
new claims 17-19 added; other claims unchanged (1 page)]

(j) applying a coating of a solderable conductive metal to said selected portions of said first surface; and
(k) sintering said conductive metal so that the conductive metal and silicon react to form a conductive metal silicide at their interface.

16. Method according to claim 15 further including the steps of contacting said l'aver of conductive metal with an etchant to remove unbonded conductive metal, and overcoating said layer of conductive metal with
additional conductive metal.

17. Method according to claim 1 wherein said plasma treatment is carried out at a frequency in the range of 35 kilohertz to 450 kilohertz.

18. Method according to claim 7 wherein step (c) is carried out at a frequency in the range of 35 kilohertz to 450 kilohertz.

19. Method according to claim 15 wherein step (c) is carried out at a frequency in the range of 35 kilohertz to 450 kilohertz.