Low-dopant polycrystalline silicon chunk
The invention provides a polycrystalline silicon chunk having a concentration of 1-50 ppta of boron and 1-50 ppta of phosphorus at the surface.
1. A polycrystalline silicon chunk having a concentration of 1-50 ppta of boron and a concentration of 1-50 ppta of phosphorus at a surface of the polycrystalline silicon chunk.
2. The polycrystalline silicon chunk as claimed in claim 1 , wherein the concentration of boron at the surface is 1-30 ppta.
3. The polycrystalline silicon chunk as claimed in claim 1 , wherein the concentration of phosphorus at the surface is 1-25 ppta.
4. The polycrystalline silicon chunk as claimed in claim 1 , having a concentration of arsenic of 0.01-10 ppta at the surface.
5. The polycrystalline silicon chunk as claimed in claim 1 , having a concentration of aluminum of 0.01-10 ppta at the surface.
6. The polycrystalline silicon chunk as claimed in claim 1 , having a concentration of metals at the surface of 10-200 pptw.
7. The polycrystalline silicon chunk as claimed in claim 1 , having the following metal concentrations at the surface:
Fe: 1-40 pptw;
Cr: 0.1-5 pptw;
Cu: 0.1-5 pptw;
Na: 1-30 pptw;
Ni: 0.1-5 pptw;
Ca: 0.1-10 pptw;
Ti: 0.1-10 pptw;
W: 0.1-10 pptw; and
Zn: 0.1-10 pptw.
8. The polycrystalline silicon chunk as claimed in claim 7 , wherein the concentration of Fe at the surface is 1-20 pptw.
9. The polycrystalline silicon chunk as claimed in claim 1 , wherein dopants are present in a bulk in the following concentrations: phosphorus 1-20 ppta, boron 1-10 ppta and arsenic 1-10 ppta.
10. The polycrystalline silicon chunk as claimed in claim 9 , wherein the dopants are present in the bulk in the following concentrations: phosphorus 1-10 ppta, boron 1-5 ppta and arsenic 1-5 ppta.
11. The polycrystalline silicon chunk as claimed in claim 2 , wherein the concentration of phosphorus at the surface is 1-25 ppta.
12. The polycrystalline silicon chunk as claimed in claim 11 , having a concentration of arsenic of 0.01-10 ppta at the surface.
13. The polycrystalline silicon chunk as claimed in claim 12 , having a concentration of aluminum of 0.01-10 ppta at the surface.
14. The polycrystalline silicon chunk as claimed in claim 13 , having a concentration of metals at the surface of 10-200 pptw.
15. The polycrystalline silicon chunk as claimed in claim 14 , having the following metal concentrations at the surface:
Fe: 1-40 pptw;
Cr: 0.1-5 pptw;
Cu: 0.1-5 pptw;
Na: 1-30 pptw;
Ni: 0.1-5 pptw;
Ca: 0.1-10 pptw;
Ti: 0.1-10 pptw;
W: 0.1-10 pptw; and
Zn: 0.1-10 pptw.
16. The polycrystalline silicon chunk as claimed in claim 15 , wherein the concentration of Fe at the surface is 1-20 pptw.
17. The polycrystalline silicon chunk as claimed in claim 16 , wherein dopants are present in a bulk in the following concentrations: phosphorus 1-20 ppta, boron 1-10 ppta and arsenic 1-10 ppta.
18. The polycrystalline silicon chunk as claimed in claim 17 , wherein the dopants are present in the bulk in the following concentrations: phosphorus 1-10 ppta, boron 1-5 ppta and arsenic 1-5 ppta.