Fused quartz crucible for producing silicon crystals, and method for producing a fused quartz crucible
AssigneeSiltronic AG
InventorsToni Lehmann, Dirk Zemke
Life of this patent
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Abstract
A fused quartz crucible for pulling a single crystal of silicon by the Czochralski technique, has an inner side with an inner layer of fused quartz that forms a surface, the inner layer being provided with a crystallization promoter which on heating of the fused quartz crucible during use, in crystal pulling, causes crystallization of fused quartz to form b-cristobalite, wherein the concentration C of synthetically obtained SiO2 at a distance d from the surface is greater than the concentration of synthetically obtained SiO2 at a distance d2 from the surface, where d2 is greater than d. Multiple crystals can be grown while maintaining high crystal quality.
Claims19
A fused quartz crucible for pulling a single crystal of silicon according to the Czochralski technique, comprising:
- an inner side on which there is located an inner layer comprising fused natural quartz and synthetically obtained SiO2, forming an inner surface, the inner layer being provided with a crystallization promoter which on heating of the fused quartz crucible during a crystal pulling, brings about crystallization of fused natural quartz and synthetically obtained SiO2 to form ß-cristobalite, wherein the concentration C of synthetically obtained SiO2 at a distance d from the inner surface of the inner layer is greater than the concentration of synthetically obtained SiO2 at a distance d2 from the surface of the inner layer, where d2 is greater than d, and the concentration C of synthetically obtained SiO2 as a function of the distance d within the inner layer is subject to the following relationships:
- C[%]<=100−(d[mm]−0.25)×30 and
- C[%]>=100−(d[mm]+0.25)×80.
A two-layer fused quartz crucible for pulling a single crystal of silicon according to the Czochralski's technique, comprising:
- an outer opaque layer comprising fused natural quartz, and an inner transparent layer comprising synthetic silica, wherein the synthetic silica content in the transparent layer varies with a distance d from an inner surface of the transparent layer such that the concentration C of synthetic silica in the transparent layer as a function of d satisfies the following relationships:
- C[%]<=100−(d[mm]−0.25)×30 and
- C[%]>=100−(d[mm]+0.25)×80,
- and an area near the inner surface of the transparent layer has a higher concentration of synthetic silica than an area closer to an inner surface of the first, outer opaque layer, and wherein the transparent layer further comprises a barium or strontium crystallization promoter within the transparent layer.
Dependencies are inferred from the claim text.