Coating compositions
View Patent ↗Silicon nitride coated crucibles for holding melted semiconductor material and for use in preparing multicrystalline silicon ingots by a directional solidification process; methods for coating crucibles; methods for preparing silicon ingots and wafers; compositions for coating crucibles and silicon ingots and wafers with a low oxygen content.
1. A composition for coating the inner surface of a crucible to improve an ingot-release characteristic of the crucible, the composition comprising a medium, silicon nitride, binder, a methyloxirane polymer dispersant and a sintering agent.
2. A composition as set forth in claim 1 wherein the silicon nitride and sintering agent are particulates that are suspended in the medium.
3. A composition as set forth in claim 1 wherein the medium is a C1 to C10 alcohol.
4. A composition as set forth in claim 1 wherein the medium is isopropyl alcohol.
5. A composition as set forth in claim 1 wherein the binder is polyvinyl butyral.
6. A composition as set forth in claim 1 comprising polyethylene glycol plasticizer.
7. A composition as set forth in claim 1 wherein the coating composition comprises at least about 0.1% by weight yttria as a sintering agent.
8. A composition as set forth in claim 1 wherein the mass ratio of sintering agent to silicon nitride in the coating composition is at least about 1:20.
9. A composition as set forth in claim 1 wherein the coating composition comprises at least about 0.1% by weight silica as a sintering agent.
10. A composition as set forth in claim 1 wherein the coating composition comprises at least about 0.1% by weight alumina as a sintering agent.
11. A composition as set forth in claim 1 wherein the coating composition comprises at least about 5% by weight silicon nitride.
12. A composition as set forth in claim 1 wherein the coating composition comprises at least about 30% by weight medium.
13. A composition for coating the inner surface of a crucible to improve an ingot-release characteristic of the crucible, the composition comprising a medium, silicon nitride, dispersant and a binder to enhance adhesion of the coating to the crucible.
14. A composition as set forth in claim 13 wherein the silicon nitride is a particulate that is suspended in the medium.
15. A composition as set forth in claim 13 wherein the medium is a C1 to C10 alcohol.
16. A composition as set forth in claim 13 wherein the binder is polyvinyl butyral.
17. A composition as set forth in claim 13 wherein the dispersant is a methyloxirane polymer.
18. A composition as set forth in claim 13 wherein the composition comprises a plasticizer.
19. A composition as set forth in claim 18 wherein the plasticizer is polyethylene glycol.
20. A composition as set forth in claim 13 wherein the coating composition comprises at least about 5% by weight silicon nitride.
21. A composition as set forth in claim 13 wherein the coating composition comprises at least about 30% by weight medium.
22. A composition as set forth in claim 1 wherein the coating composition includes at least about 0.05% by weight dispersant.
23. A composition as set forth in claim 1 wherein the coating composition includes at least about 0.5% by weight dispersant.
24. A composition as set forth in claim 1 wherein the coating composition includes at least about 1% by weight dispersant.
25. A composition for coating the inner surface of a crucible to improve an ingot-release characteristic of the crucible, the composition comprising a medium, silicon nitride, binder, polyethylene glycol plasticizer and a sintering agent.
26. A composition as set forth in claim 25 wherein the silicon nitride and sintering agent are particulates that are suspended in the medium.
27. A composition as set forth in claim 25 wherein the medium is a C1 to C10 alcohol.
28. A composition as set forth in claim 25 wherein the medium is isopropyl alcohol.
29. A composition as set forth in claim 25 wherein the binder is polyvinyl butyral.
30. A composition as set forth in claim 25 wherein the coating composition comprises at least about 0.1% by weight yttria as a sintering agent.
31. A composition as set forth in claim 25 wherein the mass ratio of sintering agent to silicon nitride in the coating composition is at least about 1:20.
32. A composition as set forth in claim 25 wherein the coating composition comprises at least about 0.1% by weight silica as a sintering agent.
33. A composition as set forth in claim 25 wherein the coating composition comprises at least about 0.1% by weight alumina as a sintering agent.
34. A composition as set forth in claim 25 wherein the coating composition comprises at least about 5% by weight silicon nitride.
35. A composition as set forth in claim 25 wherein the coating composition comprises at least about 30% by weight medium.
36. A composition as set forth in claim 25 wherein the coating composition comprises at least about 0.5% by weight plasticizer.
37. A composition as set forth in claim 25 wherein the coating composition comprises at least about 2% by weight plasticizer.
38. A composition as set forth in claim 25 wherein the coating composition comprises at least about 5% by weight plasticizer.