Silica glass crucible for pulling up silicon single crystal, method for manufacturing thereof and method for manufacturing silicon single crystal
A silica glass crucible for pulling up a silicon single crystal including a wall part and a bottom part is provided with a natural silica glass layer which forms at least one part of a an inner surface of the bottom part, and a synthetic silica glass layer which forms at least an inner surface of the wall part, wherein a concentration of Ca included in the natural silica glass layer is 0.5 ppm or less.
1. A silica glass crucible for pulling up a silicon single crystal including a wall part and a bottom part comprising:
a first natural silica glass layer which forms at an outer layer in the wall part and the bottom part;
a synthetic silica glass layer which forms an inner layer in the wall part and the bottom part, and which is exposed in at least the wall part; and
a second natural silica glass layer which covers a region which includes the center of the bottom part among the inner surfaces of the synthetic silica glass layer; wherein
a concentration of Ca included in the second natural silica glass layer is 0.5 ppm or less, and a thickness of the second natural silica glass layer is 30 μm or more and 200 μm or less.
2. The silica glass crucible as claimed in claim 1 , wherein a flat region of the second natural silica glass layer includes a projection plane of the silicon single crystal.
3. The silica glass crucible as claimed in claim 2 , wherein a diameter of the flat region of the second natural silica glass layer is 0.3R 0 or more and 0.6R 0 or less with respect to a diameter R 1 of an opening of the crucible.
4. The silica glass crucible as claimed in claim 1 , wherein a concentration of Ca included in the second natural silica glass layer is 0.4 ppm or less.
5. The silica glass crucible as claimed in claim 1 , wherein a thickness of the second natural silica glass layer is 30 μm or more and 100 μm or less.