Vitreous silica crucible and method of manufacturing the same
Provided is a method of manufacturing a vitreous silica crucible for pulling a silicon single crystal which can suppress melt surface vibration of silicon melt filled therein and has a long lifetime. The crucible includes a peripheral wall portion, a curved portion and a bottom portion, and has a plurality of micro recesses on the specific region of the inner surface of the peripheral wall portion.
1. A method of manufacturing a vitreous silica crucible for pulling a silicon single crystal, the crucible comprising a peripheral wall portion, a curved portion and a bottom portion and having an outer layer of a natural fused silica layer and an inner layer of a synthetic fused silica layer, the method comprising the processes of:
forming an outer layer of natural silica powder;
forming an inner layer of synthetic silica powder on an inner surface of the outer layer;
forming a vitreous silica crucible having a peripheral wall portion, a curved portion and a bottom portion by fusing the layers from an inner surface side of the inner layer by arc discharge;
forming a plurality of micro recesses in a specific region by use of physical processing using a carbon dioxide laser or diamond tool after the process of forming the vitreous silica crucible; and
removing processing strain introduced in the process of forming the micro recesses by heat-treating the vitreous silica crucible at a temperature of 1200 to 1400 deg. C. for 5 minutes to one hour;
wherein the thickness of the peripheral wall portion is in the range of 100 μm to 1000 μm;
the specific region is located in a region of 0.60 H to 0.90 H from the bottom portion, where H is a height of the vitreous silica crucible;
the specific region is divided into ring-shaped inner portions each having a width of 0.2 mm to 4.0 mm and the specific region has at least one micro recess in each of the ring-shaped inner portions;
the average diameter of the micro recesses is in the range of 10 μm to 300 μm;
the average depth of the micro recesses is in the range of 0.10% to 30% of the thickness of the crucible in the peripheral wall portion; and
the ratio of the average diameter to the average depth, of the micro recesses, is less than 0.7.
2. A method of manufacturing a vitreous silica crucible for pulling a silicon single crystal, the crucible comprising a peripheral wall portion, a curved portion and a bottom portion and having an outer layer of a natural fused silica layer and an inner layer of a synthetic fused silica layer, the method comprising the processes of:
forming an outer layer of natural silica powder;
forming an inner layer of synthetic silica powder on an inner surface of the outer layer;
forming a vitreous silica crucible having a peripheral wall portion, a curved portion and a bottom portion by fusing the layers from an inner surface side of the inner layer by arc discharge;
forming a plurality of micro recesses in a specific region by use of physical processing using a carbon dioxide laser or diamond tool after the process of forming the vitreous silica crucible; and
removing processing strain introduced in the process of forming the micro recesses by acid-treating the vitreous silica crucible one to ten times with an aqueous solution of hydrofluoric acid having a hydrogen fluoride concentration of 20% to 30%;
wherein the thickness of the peripheral wall portion is in the range of 100 μm to 1000 μm;
the specific region is located in a region of 0.60 H to 0.90 H from the bottom portion, where H is a height of the vitreous silica crucible;
the specific region is divided into ring-shaped inner portions each having a width of 0.2 mm to 4.0 mm and the specific region has at least one micro recess in each of the ring-shaped inner portions;
the average diameter of the micro recesses is in the range of 10 μm to 300 μm;
the average depth of the micro recesses is in the range of 0.10% to 30% of the thickness of the crucible in the peripheral wall portion; and
the ratio of the average diameter to the average depth, of the micro recesses, is less than 0.7.