Silicon block, method for producing the same, crucible of transparent or opaque fused silica suited for performing the method, and method for the production thereof

Patent metadata

Field	Value
Publication number	US-9828691-B2
Application number	US-201514817839-A
Country	US
Kind code	B2
Filing date	Aug 4, 2015
Priority date	Aug 4, 2014
Publication date	Nov 28, 2017
Grant date	Nov 28, 2017

Abstract

A method for producing a solar crucible includes providing a crucible base body of transparent or opaque fused silica having an inner wall, providing a dispersion containing amorphous SiO 2 particles, applying a SiO 2 -containing slip layer to at least a part of the inner wall by using the dispersion, drying the slip layer to form a SiO 2 -containing grain layer and thermally densifying the SiO 2 -containing grain layer to form a diffusion barrier layer. The dispersion contains a dispersion liquid and amorphous SiO 2 particles that form a coarse fraction and a fine fraction with SiO 2 nanoparticles. The weight percentage of the SiO 2 nanoparticles based on the solids content of the dispersion is in the range between 2 and 15% by weight. The SiO 2 -containing grain layer is thermally densified into the diffusion barrier layer through the heating up of the silicon in the crystal growing process.

First claim

The invention claimed is:

1. A method for producing a solar crucible with a rectangular shape for use in a crystal growing process for silicon, the method comprising:
providing a crucible base body of transparent or opaque fused silica comprising an inner wall;
providing a dispersion containing amorphous SiO 2 particles;
applying a SiO 2 -containing slip layer with a layer thickness of at least 0.1 mm to at least a part of the inner wall by using the dispersion;
drying the slip layer so as to form a SiO 2 -containing grain layer having a casting skin; and
thermally densifying the SiO 2 -containing grain layer so as to form a diffusion barrier layer,
wherein the dispersion contains a dispersion liquid and the amorphous SiO 2 particles that form a coarse fraction with particle sizes in the range between 1 μm and 50 μm and a fine fraction with SiO 2 nanoparticles with particle sizes of less than 100 nm, the fine fraction with the SiO 2 nanoparticles with particle sizes of less than 100 nm accounting for a volume proportion of the casting skin of more than 70%,
wherein a weight percentage of the SiO 2 nanoparticles based on a solids content of the dispersion is in the range between 2 and 15% by wt., and
wherein the SiO 2 -containing grain layer is thermally densified into the diffusion barrier layer through heating up of the silicon in the crystal growing process.

2. The method according to claim 1 , wherein the solids content of the dispersion is less than 80% by wt.

3. The method according to claim 1 , wherein the dispersion is free of binders, wherein the SiO 2 content of the amorphous SiO 2 particles is at least 99.99% by wt., and wherein a total content of metallic impurities of transition elements is less than 5 wt. ppm.

4. The method according to claim 1 , wherein the slip layer is applied by casting the dispersion onto the inner wall.

5. The method according to claim 1 , wherein the inner wall is moistened prior to the application of the slip layer, and wherein the inner wall of the crucible base body is a porous inner wall.

6. The method according to claim 1 , wherein a green layer obtained after drying of the slip layer has a layer thickness in the range of 0.1-1.5 mm.

7. A method for producing a silicon block in a crystal growing process comprising:
providing a solar crucible with a crucible base body of transparent or opaque fused silica comprising an inner wall, of which at least a part is covered by a SiO 2 -containing grain layer having a casting skin; and
filling the solar crucible with silicon, the silicon being heated so as to form a silicon melt, the silicon melt being cooled down with crystallization and formation of the silicon block,
wherein the SiO 2 -containing grain layer contains amorphous SiO 2 particles that form a coarse fraction with particle sizes in the range between 1 μm and 50 μm and a fine fraction of SiO 2 nanoparticles with particle sizes of less than 100 nm, the fine fraction of SiO 2 nanoparticles with particle sizes of less than 100 nm accounting for a volume proportion of the casting skin of more than 70%,
wherein the weight percentage of the SiO 2 nanoparticles of the SiO 2 -containing grain layer is in the range between 2 and 15% by wt., and
wherein the SiO 2 -containing grain layer is thermally densified during heating up of the silicon.

8. The method according to claim 7 , wherein before the formation of the silicon melt, the SiO 2 -containing grain layer has reached a density of more than 90% of its theoretical density.

Assignees

• Heraeus Quarzglas
• Heraes Quarzglas Gmbh & Co Kg

Inventors

• Schenk Christian
• Scheich Gerrit
• Nielsen Nils-Christian
• Lehmann Walter
• Freudenberg Bernhard
• Dadzis Kaspars
• Nadolny Sandra
• Wolny Franziska
• Fischer Gerd

Classifications

• C30B35/002

  Crucibles or containers · CPC title

• C30B29/06

  Silicon · CPC title

• C03B19/09

  by fusing powdered glass in a shaping mould · CPC title

• C03B2201/03

  Impurity concentration specified · CPC title

• C30B11/002 Primary

  Crucibles or containers for supporting the melt · CPC title