Vitreous silica crucible having transparent layer, bubble-containing layer, and semi-transparent layer in its wall, method of manufacturing the same, and method of manufacturing silicon ingot
Provided is a vitreous silica crucible which can suppress inward sagging and buckling of the sidewall effectively even when time for pulling silicon ingots is extremely long. According to the present invention, provided is a vitreous silica crucible for pulling a silicon single crystal, wherein the crucible has a wall comprising, from an inner surface toward an outer surface of the crucible, a transparent vitreous silica layer having a bubble content rate of less than 0.5%, a bubble-containing vitreous silica layer having a bubble content rate of 1% or more and less than 50%, a semi-transparent vitreous silica layer having a bubble content rate of 0.5% or more and less than 1.0% and having an OH group concentration of 35 ppm or more and less than 300 ppm.
1. A vitreous silica crucible for pulling a silicon single crystal, wherein the crucible has a wall comprising, from an inner surface toward an outer surface of the crucible,
a transparent vitreous silica layer having a bubble content rate of less than 0.5% and having an OH group concentration of 30 ppm or less,
a first bubble-containing vitreous silica layer having a bubble content rate of 1% or more and less than 50%,
a semi-transparent vitreous silica layer having a bubble content rate of 0.5% or more and less than 1.0% and having an OH group concentration of 35 ppm or more and less than 300 ppm, and
a second bubble-containing vitreous silica layer having a bubble content rate of 1% or more and less than 50%;
wherein the first bubble-containing vitreous silica layer comprises an impurity-containing vitreous silica layer to which impurities are added acting as nuclei when turning the vitreous silica into crystalline silica in a high temperature environment, wherein a concentration of impurities in the impurity-containing vitreous silica layer is 20 ppm or higher and is higher than that in the neighboring layers, and
wherein the total thickness of the first and second bubble-containing vitreous silica layers is 50% or less of the thickness of the wall.
2. The crucible of claim 1 , wherein the thickness of the semi-transparent vitreous silica layer is 10% to 60% of the thickness of the wall of the crucible.
3. The crucible of claim 1 , wherein the second bubble-containing vitreous silica layer on the outer side of the semi-transparent vitreous silica layer comprises an impurity-containing vitreous silica layer to which are added acting as nuclei when turning the vitreous silica into crystalline silica in a high temperature environment.
4. The crucible of claim 1 , wherein the impurity-containing vitreous silica layer contains the impurities in an amount of 20 ppm to 500 ppm.
5. The crucible of claim 1 , wherein the impurity-containing vitreous silica layer has a thickness which is 50% to 90% of a thickness of the bubble-containing vitreous silica layer.