Compositions and methods for texturing polycrystalline silicon wafers
View Patent ↗Compositions and methods for chemical texturing a surface of a polycrystalline silicon wafer to be used in the manufacture of solar cells provide increased efficiency in the manufacture and operation of solar cells. The compositions and methods disclosed herein include first and second components, wherein the first component is a UKON etch composition, including a hydrofluoric acid/nitric acid mixture and water, while the second component includes a silicon wafer texturing enhancer (SWTE).
1. A silicon wafer texturing enhancer (SWTE) for use in a UKON etch process, comprising a multi-component process window enhancer in an aqueous system in an amount sufficient to optimize the processing window in a UKON etch process.
2. The silicon wafer texturing enhancer (SWTE) according to claim 1 further comprising an etch defect passivator.
3. The silicon wafer texturing enhancer (SWTE) according to claim 1 wherein said UKON etch process includes a UKON etch composition comprising a hydrofluoric acid/nitric acid mixture and water.
4. The silicon wafer texturing enhancer (SWTE) according to claim 1 wherein said UKON etch process composition has a ratio of hydrofluoric acid/nitric acid of from about 0.250 to about 0.550.
5. The silicon wafer texturing enhancer (SWTE) according to claim 1 wherein said multi-component process window enhancer comprises sulfuric acid and at least one of phosphoric acid or DTPMP.
6. The silicon wafer texturing enhancer (SWTE) according to claim 5 wherein said multi-component process window enhancer comprises sulfuric acid and phosphoric acid.
7. The silicon wafer texturing enhancer (SWTE) according to claim 5 wherein said multi-component process window enhancer comprises sulfuric acid and DTPMP.
8. The silicon wafer texturing enhancer (SWTE) according to claim 2 further comprising citric acid.
9. The silicon wafer texturing enhancer (SWTE) according to claim 1 comprising water, sulfuric acid, citric acid, and phosphoric acid.
10. The silicon wafer texturing enhancer (SWTE) according to claim 9 wherein sulfuric acid comprises from about 3.00% to about 11.00% by weight of the SWTE, citric acid comprises from about 4.00% to about 12.00% by weight of the SWTE, phosphoric acid comprises from about 35.00% to about 45.00% by weight of the SWTE, and water comprises from about 40.00% to about 50.00% by weight of the SWTE.
11. The silicon wafer texturing enhancer (SWTE) according to claim 9 additionally comprising boric acid.
12. The silicon wafer texturing enhancer (SWTE) according to claim 11 wherein sulfuric acid comprises from about 1.00% to about 3.25% by weight of the SWTE, citric acid comprises from about 1.50% to about 3.75% by weight of the SWTE, phosphoric acid comprises from about 8.00% to about 18.00% by weight of the SWTE, boric acid comprises from about 1.50% to about 3.75% by weight of the SWTE, and water comprises from about 74.00% to about 84.00% by weight of the SWTE.
13. The silicon wafer texturing enhancer (SWTE) according to claim 1 comprising water, sulfuric acid, and DTPMP.
14. The silicon wafer texturing enhancer (SWTE) according to claim 13 wherein sulfuric acid comprises from about 3.00% to about 11.00% by weight of the SWTE, DTPMP comprises from about 40.00% to about 54.00% by weight of the SWTE, and water comprises from about 39.00% to about 51.00% by weight of the SWTE.
15. The silicon wafer texturing enhancer (SWTE) according to claim 13 additionally comprising boric acid.
16. The silicon wafer texturing enhancer (SWTE) according to claim 15 wherein sulfuric acid comprises from about 1.25% to about 3.25% by weight of the SWTE, DTPMP comprises from about 11.00% to about 19.00% by weight of the SWTE, boric acid comprises from about 1.50% to about 3.75% by weight of the SWTE, and water comprises from about 70.00% to about 88.00% by weight of the SWTE.
17. The silicon wafer texturing enhancer (SWTE) according to claim 1 comprising water, sulfuric acid, citric acid, DTPMP, and phosphoric acid.
18. The silicon wafer texturing enhancer (SWTE) according to claim 17 wherein sulfuric acid comprises from about 2.00% to about 6.00% by weight of the SWTE, citric acid comprises from about 2.25% to about 6.50% by weight of the SWTE, phosphoric acid comprises from about 19.00% to about 29.00% by weight of the SWTE, DTPMP comprises from about 22.00% to about 32.00% by weight of the SWTE, and water comprises from about 35.00% to about 45.00% by weight of the SWTE.
19. The silicon wafer texturing enhancer (SWTE) according to claim 17 additionally comprises boric acid.
20. The silicon wafer texturing enhancer (SWTE) according to claim 19 wherein sulfuric acid comprises from about 1.25% to about 2.75% by weight of the SWTE, citric acid comprises from about 1.50% to about 3.25% by weight of the SWTE, phosphoric acid comprises from about 6.00% to about 16.50% by weight of the SWTE, DTPMP comprises from about 8.00% to about 18.00% by weight of the SWTE, boric acid comprises from about 1.50% to about 2.25% by weight of the SWTE, and water comprises from about 58.00% to about 78.00% by weight of the SWTE.
21. A method of chemically texturing a surface of a polycrystalline silicon wafer, said method comprising contacting said surface of said polycrystalline silicon wafer with a composition for a time and at a temperature sufficient to texturize said wafer surface, said composition comprising first and second components, wherein said first component comprises a hydrofluoric acid/nitric acid mixture and water, and said second component comprises a silicon wafer texturing enhancer (SWTE).
22. The method according to claim 21 wherein the surface of the wafer is contacted with said composition at a temperature of about 2° C. to about 30° C. for a period of time of about 20 seconds to about 90 seconds.
23. The method according to claim 21 wherein the surface of the wafer is contacted with said composition at a temperature of about 12° C. to about 16° C. for a period of time of about 30 seconds to about 60 seconds.
24. A composition for chemical texturing a surface of a polycrystalline silicon wafer, said composition comprising first and second components, wherein said first component comprises a hydrofluoric acid/nitric acid mixture and water, and said second component comprises a silicon wafer texturing enhancer (SWTE).