US5011567A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of fabricating solar cells
Assignee: Schott Solar CSP Inc
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Filing: 1990-07-17
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Granted: 1991-04-30
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Expires: 2010-07-17
Abstract
Abstract A method of forming a metallization pattern on a solar cell substrate having an outer layer of a selected dielectric such as silicon nitride, silicon dioxide, or glass, by removing selected portions of the dielectric layer with a laser beam. This laser exposure drives portions of the P/N junction positioned beneath the exposed regions of the substrate more deeply into the substrate. Removal of selected portions of the dielectric layer exposes regions of the silicon substrate on which conductors may be deposited by conventional immersion plating methods. This laser removal of the dielectric layer is effected in an environment substantially free of chemical etching substances. Following removal of the selected portions of the dielectric layer, the substrate is preferably immersed in a buffered oxide etch solution to remove residual silicon dioxide and is then preferably immersed in a high ratio (nitric acid to hydrofluoric acid) etch solution to remove residual silicon nitride. The method of forming a metallization pattern may be incorporated into a comprehensive solar cell fabrication process.
Inventors
- 👤 Ronald C. Gonsiorawski
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 03:05
CPC Classifications
H; H10; H10F; H10F71/00; H10F71/121; H10F77/00; H10F77/20; H10F77/206; H10F77/211; Y; Y02; Y02E; Y02E10/00; Y02E10/50; Y02E10/547; Y02P; Y02P70/00; Y02P70/50
Claims Analysis
Total Claims: 34
Claim 1
Independent Claim
180 words
A method of forming a pattern for metal deposition on a photovoltaic cell substrate comprising in sequence the steps of: (a) providing a silicon substrate having a dielectric layer on one side thereof, said substrate having a P/N junction formed therein adjacent said one side; (b) subjecting said dielectric layer to a laser beam of an intensity and for a duration sufficient to eliminate selected portions of said dielectric layer and thereby expose sections of said silicon substrate without forming apertures in said substrate extending through said P/N junction or otherwise causing degradation of said P/N junction, said selected portions of said dielectric layer being eliminated in an environment that is substantially free of gaseous, liquid or solid chemical etching substances; and (c) immersing said silicon substrate in at least one selected etchant for a predetermined period of time, said etchant and period of time being selected so that said etchant will remove substantially all residual silicon nitride and silicon oxide deposits on the sections of said silicon substrate exposed by elimination of said selected portions of said dielectric layer.
Claim 2
Independent Claim
180 words
A method of forming a pattern for metal deposition on a photovoltaic cell substrate comprising in sequence the steps of: (a) providing a silicon substrate having a dielectric layer on one side thereof, said substrate having a P/N junction formed therein adjacent said one side; (b) subjecting said dielectric layer to a laser beam of an intensity and for a duration sufficient to eliminate selected portions of said dielectric layer and thereby expose sections of said silicon substrate without forming apertures in said substrate extending through said P/N junction or otherwise causing degradation of said P/N junction, said selected portions of said dielectric layer being eliminated in an environment that is substantially free of gaseous, liquid or solid chemical etching substances; and (c) immersing said silicon substrate in at least one selected etchant for a predetermined period of time, said etchant and period of time being selected so that said etchant will remove substantially all residual silicon nitride and silicon oxide deposits on the sections of said silicon substrate exposed by elimination of said selected portions of said dielectric layer.
Claim 3
Dependent Claim
15 words
A method according to claim 1 wherein said dielectric layer is made of silicon nitride.
Claim 4
Dependent Claim
14 words
A method according to claim 1 wherein said dielectric layer is made of glass.
Claim 5
Dependent Claim
16 words
A method according to claim 1 wherein said laser beam is generated by a Nd:YAG laser.
Claim 6
Dependent Claim
57 words
A method according to claim 1 wherein said subjecting step is effected by moving said laser beam relative to said substrate, and further wherein said laser beam is pulsed on and off in sequence with movement of said substrate so as to create a pattern for metallization comprising the image of a conventional solar cell grid electrode.
Claim 7
Dependent Claim
38 words
A method according to claim 1 wherein said intensity and duration of exposure of said laser beam are additionally selected so as drive those portions of said P/N junction positioned below said selected portions deeper into said substrate.
Claim 8
Dependent Claim
18 words
A method according to claim 4 wherein said silicon substrate is polycrystalline silicon produced by the EFG process.
Claim 9
Dependent Claim
24 words
A method according to claim 1 wherein said selected portions of said substrate are eliminated by said laser beam in a substantially inert atmosphere.
Claim 10
Dependent Claim
43 words
A method according to claim 1 wherein said subjecting step includes eliminating a plurality of substantially circular portions of said dielectric layer so as to expose said sections of said silicon substrate, said plurality of substantially circular portions together defining said selected portions.
Claim 11
Dependent Claim
20 words
A method according to claim 9 wherein said plurality of substantially circular portions are aligned in one or more rows.
Claim 12
Dependent Claim
20 words
A method according to claim 9 wherein each of said plurality of circular portions is spaced from adjacent circular portions.
Claim 13
Dependent Claim
18 words
A method according to claim 9 wherein each of said plurality of circular portions overlaps adjacent circular portions.
Claim 14
Dependent Claim
32 words
A method according to claim 11 wherein said circular portions have a diameter ranging from 20 to 250 microns and adjacent circular portions are spaced apart 0 (zero) microns to 15 microns.
Claim 15
Dependent Claim
41 words
A method according to claim 1 wherein said immersing step comprises: immersing said substrate in a buffered oxide etch; and removing said substrate from said buffered oxide etch after said substrate has been immersed therein for a selected period of time.
Claim 16
Dependent Claim
23 words
A method according to claim 14 wherein said buffered oxide etch comprises ammonium fluoride buffering salts, water and 10-12% hydrofluoric acid by weight.
Claim 17
Dependent Claim
32 words
A method according to claim 14 wherein said selected period of time is equal to about 30 seconds when said buffered oxide etch is maintained at a temperature of about 22° C.
Claim 18
Dependent Claim
46 words
A method according to claim 14 wherein said selected period of time is chosen so that said buffered oxide etch removes substantially all of the silicon dioxide present on the sections of said substrate exposed by said elimination of said selected portions of said dielectric layer.
Claim 19
Dependent Claim
28 words
A method according to claim 14 further including the step of rinsing said substrate in de-ionized water after said substrate has been removed from said buffered oxide etch.
Claim 20
Dependent Claim
47 words
A method according to claim 1 wherein said immersing step comprises: immersing said substrate in a high ratio etch comprising nitric acid and hydrofluoric acid; and removing said substrate from said high ratio etch after said substrate has been immersed therein for a selected period of time.
Claim 21
Dependent Claim
25 words
A method according to claim 19 wherein the ratio of nitric acid to hydrofluoric acid in said high ratio etch ranges from 50:1 to 1000:1.
Claim 22
Dependent Claim
23 words
A method according to claim 19 wherein the ratio of nitric acid to hydrofluoric acid in said high ratio etch is about 300:1.
Claim 23
Dependent Claim
32 words
A method according to claim 19 wherein said selected period of time is equal to about 20 seconds when said high ratio etch is maintained at a temperature of about 12° C.
Claim 24
Dependent Claim
46 words
A method according to claim 19 wherein said selected period of time is chosen so that said high ratio etch removes substantially all of the silicon nitride present on the sections of said substrate exposed by said elimination of said selected portions of said dielectric layer.
Claim 25
Dependent Claim
28 words
A method according to claim 19 further including the step of immersing said substrate in de-ionized water after said substrate has been removed from said high ratio etch.
Claim 26
Dependent Claim
56 words
A method according to claim 14 including, following removal of said substrate from said buffered oxide etch, the steps of: immersing said substrate in a high ratio etch comprising nitric acid and hydrofluoric acid; and removing said substrate from said high ratio etch after said substrate has been immersed therein for a selected period of time.
Claim 27
Independent Claim
157 words
A method of forming a metallization pattern on a photovoltaic cell substrate comprising in sequence the steps of: (a) providing a flat silicon substrate having a P/N junction formed therein adjacent one side thereof and a layer of silicon nitride covering said one side; (b) scanning selected portions of said silicon nitride layer of said substrate with a laser beam of an intensity and for a duration sufficient to remove said selected portions and expose selected areas of said one side to which electrodes may be deposited, said selected portions being removed in an environment substantially free of chemical etching substances; (c) immersing said substrate in a buffered oxide etch solution for a period of time sufficient to remove residual silicon dioxide on said selected areas; and (d) immersing said substrate in a high ratio etch comprising nitric acid and hydrofluoric acid for a period of time sufficient to remove residual silicon nitride on said selected areas.
Claim 28
Independent Claim
157 words
A method of forming a metallization pattern on a photovoltaic cell substrate comprising in sequence the steps of: (a) providing a flat silicon substrate having a P/N junction formed therein adjacent one side thereof and a layer of silicon nitride covering said one side; (b) scanning selected portions of said silicon nitride layer of said substrate with a laser beam of an intensity and for a duration sufficient to remove said selected portions and expose selected areas of said one side to which electrodes may be deposited, said selected portions being removed in an environment substantially free of chemical etching substances; (c) immersing said substrate in a buffered oxide etch solution for a period of time sufficient to remove residual silicon dioxide on said selected areas; and (d) immersing said substrate in a high ratio etch comprising nitric acid and hydrofluoric acid for a period of time sufficient to remove residual silicon nitride on said selected areas.
Claim 29
Dependent Claim
40 words
A method according to claim 26 wherein said scanning step includes removing from said dielectric layer a plurality of substantially circular portions arranged so as to form at least one row, said plurality of circular portions defining said selected portions.
Claim 30
Dependent Claim
62 words
A method according to claim 26 further wherein said first immersing step comprises removing said substrate from said buffered oxide etch after said selected period of time and rinsing said substrate with de-ionized water, and said second immersing step comprises removing said substrate from said high ratio etch solution after said selected period of time and rinsing said substrate with de-ionized water.
Claim 31
Independent Claim
201 words
A method of fabricating solar cells comprising in sequence the steps of: (a) providing a silicon substrate having a dielectric layer on one side thereof, said substrate having a P/N junction formed therein adjacent said one side; (b) subjecting said dielectric layer to a laser beam of an intensity and for a duration sufficient to eliminate selected portions of said dielectric layer and expose selected sections of said substrate, said selected portions of said dielectric layer being eliminated in an environment that is substantially free of gaseous, liquid or solid chemical etching substances; (c) applying an aluminum layer to an opposite side of said substrate; (d) immersing said substrate in a buffered oxide etch; (e) removing said substrate from said buffered oxide etch after said substrate has been immersed therein for a selected period of time; (f) immersing said substrate in a high ratio etch comprising nitric acid and hydrofluoric acid; (g) removing said substrate from said high ratio etch after said substrate has been immersed therein for a selected period of time; and (h) plating a nickel layer over (a) sections of said substrate exposed by removal of said selected portions of said dielectric layer and (b) said aluminum layer.
Claim 32
Independent Claim
201 words
A method of fabricating solar cells comprising in sequence the steps of: (a) providing a silicon substrate having a dielectric layer on one side thereof, said substrate having a P/N junction formed therein adjacent said one side; (b) subjecting said dielectric layer to a laser beam of an intensity and for a duration sufficient to eliminate selected portions of said dielectric layer and expose selected sections of said substrate, said selected portions of said dielectric layer being eliminated in an environment that is substantially free of gaseous, liquid or solid chemical etching substances; (c) applying an aluminum layer to an opposite side of said substrate; (d) immersing said substrate in a buffered oxide etch; (e) removing said substrate from said buffered oxide etch after said substrate has been immersed therein for a selected period of time; (f) immersing said substrate in a high ratio etch comprising nitric acid and hydrofluoric acid; (g) removing said substrate from said high ratio etch after said substrate has been immersed therein for a selected period of time; and (h) plating a nickel layer over (a) sections of said substrate exposed by removal of said selected portions of said dielectric layer and (b) said aluminum layer.
Claim 33
Dependent Claim
53 words
A method according to claim 29 wherein said subjecting step includes eliminating a plurality of substantially circular portions of said dielectric layer so as to expose said selected sections of said substrate, said plurality of circular portions (a) being positioned in a row and (b) defining said selected portions of said dielectric layer.
Claim 34
Dependent Claim
26 words
A method according to claim 14 wherein said buffered oxide etch comprises by weight about 40% ammonium fluoride buffering salts, 11% hydrofluoric acid, and 49% water.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-04-29 | 1994-10-29 | 1995-04-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-04-29 | 1998-10-29 | 1999-04-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-04-29 | 2002-10-29 | 2003-04-30 | $7700.00 | Window Closed / Lapsed |