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, 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 C 1 to C 10 alcohol.
4. A composition for coating the inner surface of a crucible to improve an ingot-release characteristic of the crucible, the composition comprising a medium comprising isopropyl alcohol, silicon nitride, binder, and a sintering agent.
5. A composition as set forth in claim 1 wherein the binder is polyvinyl butyral.
6. 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.
7. 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.
8. 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.
9. 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.
10. A composition as set forth in claim 1 wherein the coating composition comprises at least about 5% by weight silicon nitride.
11. A composition as set forth in claim 1 wherein the coating composition comprises at least about 15% by weight silicon nitride.
12. A composition as set forth in claim 1 wherein the coating composition comprises at least about 30% by weight silicon nitride.
13. A composition as set forth in claim 1 wherein the coating composition comprises at least about 30% by weight medium.
14. A composition as set forth in claim 1 wherein the coating composition comprises at least about 0.5% by weight binder.
15. A composition as set forth in claim 1 wherein the coating composition comprises at least about 5% by weight binder.
16. A composition as set forth in claim 1 wherein the coating composition includes at least about 0.5% by weight dispersant.
17. A composition as set forth in claim 1 wherein the coating composition includes at least about 1% by weight dispersant.
18. A composition as set forth in claim 1 wherein the coating composition comprises at least about 0.5% by weight plasticizer.
19. 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, and more than one sintering agent selected from the group consisting of silica, alumina, and yttria.
20. A composition as set forth in claim 19 wherein the coating composition comprises at least about 0.1% by weight silica and at least about 0.1% by weight alumina as the sintering agent.
21. A composition as set forth in claim 19 wherein the coating composition comprises at least about 0.1% by weight silica and at least about 0.1% by weight yttria as the sintering agent.
22. A composition as set forth in claim 19 wherein the coating composition comprises at least about 0.1% by weight alumina and at least about 0.1% by weight yttria as the sintering agent.