High-purity vitreous silica crucible used for pulling large-diameter single-crystal silicon ingot
A high-purity vitreous silica crucible which has high strength and is used for pulling a large-diameter single-crystal silicon ingot, includes a double laminated structure constituted by an outer layer composed of amorphous silica glass with a bubble content of 1 to 10% and a purity of 99.99% or higher and an inner layer composed of amorphous silica glass with a bubble content of 0.6% or less and a purity of 99.99% or higher, and in the portion between the upper opening end of the high-purity vitreous silica crucible and the ingot-pulling start line of a silicon melt surface in the step of pulling a single-crystal silicon ingot, a portion corresponding to 40 to 100 volume % from the upper opening end of the crucible is in a crystalline structure free from the crystallization promoter.
1. A high-purity vitreous silica crucible having an inner diameter of 610 to 810 mm and used for pulling a single-crystal silicon ingot with a diameter of 200 to 300 mm, the crucible comprising:
a double laminated structure constituted by an outer layer composed of amorphous vitreous silica with a bubble content of 1 to 10% and a purity of 99.99% or higher and an inner layer composed of amorphous silica glass with a bubble content of 0.6% or less and a purity of 99.99% or higher, wherein:
40 to 100 volume % of the inner layer of the crucible from the upper opening end of the crucible to 40 or 50 mm below the upper opening end is in a crystalline structure free from a crystallization promoter, the volume % of the crystalline being observed using an optical microscope,
the remainder of the inner layer of the crucible is in the amorphous silica glass structure free from the crystallization promoter,
thickness of the inner layer is 2 mm, and
the volume % of the entire portion from the upper opening end of the crucible to 40 or 50 mm below the upper opening end is established as 100 volume %, and the volume % of the crystalline structure with respect to the 100 volume % is represented as the crystallization rate.