US 5,394,830 A · Apparatus and method for growing long single crystals in a liquid encapsulated Czochralski process

Abstract

Apparatus and method are provided for growing improved quality long and large single crystals in a liquid encapsulated Czochralski (LEC) process, in which a separate cooling circuit is provided for the upper portion of a vessel which cools that portion independently of any cooling means for the lower portion of the vessel, and in which the gas flow pattern can desirably be controlled such that the gas flow is predominantly downward adjacent the vessel wall, and predominantly upward near the center of the vessel, where the crystal is being pulled from the melt. The apparatus is also provided with a thermal shielding device having an inner and an outer shield tube, connected in fixed positions to a flange member which extends radially from the inner shield tube to a point immediately adjacent the vessel side wall, with the inner shield being disposed to prevent direct radiative heat transfer from the wall of a crucible holding a melt of the material to be pulled into the crystal, to the crystal being pulled from the melt in the crucible. The outer shield tube, the flange member, a lower barrier, and the vessel wall define the boundaries of a convective cell which desirably regulates, to make uniform, the thermal environment to which the crucible is exposed when raised from the region in which it is surrounded by a heater.

Claims26

Dependent claims

An apparatus for growing long single crystals in a liquid encapsulated Czochralski process, comprising:

vessel means defining a generally enclosed axially extending volume;
means for containing a melt of material to be grown into a crystal, said melt containing means being disposed in a lower portion of said enclosed volume of said vessel means;
heater means for maintaining said melt of material in said melt-containing means in a desired bulk thermal condition, said heater means also being disposed in a lower portion of said enclosed volume of said vessel means;
and
first means for cooling an upper portion of a side wall of said vessel means independently of a lower portion of said side wall of said vessel means, said first cooling means further having means for maintaining an axial temperature gradient in said upper portion of said side wall in which an uppermost extent of said upper portion is maintained at a lower temperature than a lowermost extend of said upper portion.

2 more elements

An apparatus for growing long single crystals in a liquid encapsulated Czochralski process, comprising:

vessel means defining a generally enclosed axially extending volume, said enclosed volume being bounded on its sides by a vessel side wall;
means for containing a melt of material to be grown into a crystal, said melt containing means being disposed in a lower portion of said enclosed volume of said vessel means;
means for pulling a crystal from said melt of material at an approximately central region of said melt containing means;
and
shielding means comprising a first shield tube for thermally shielding said crystal being pulled from an inner surface of an upwardly extending side wall of said melt containing means, to substantially prevent direct radiative exchange between said crystal being pulled and said upwardly extending sidewall, said shielding means extending downwardly into said melt containing means to a height at which said crystal being pulled emerges from a melt encapsulant covering said melt.

2 more elements

An apparatus for growing long single crystals in a liquid encapsulated Czochralski process, comprising:

vessel means defining a generally enclosed axially extending volume, said enclosed volume being bounded on its sides by a vessel side wall;
means for containing a melt of material to be grown into a crystal, said melt containing means being disposed in a lower portion of said enclosed volume of said vessel means;
means for pulling a crystal from said melt of material at an approximately central region of said melt containing means;
and
a convective cell disposed radially outwardly and axially immediately above an initial height of said melt containing means, a radial inner boundary of said convective cell comprising an outer shield tube having a diameter large enough to surround an outer surface of said melt containing means without making contact therewith, a radial outer boundary of said convective cell comprising said vessel side wall, said convective cell further having upper and lower barrier means spanning nearly an entire distance between said inner and outer boundaries of said convective cell.

2 more elements

Dependencies are inferred from the claim text.

Apparatus and method for growing long single crystals in a liquid encapsulated Czochralski process

Life of this patent

Apparatus and method for growing long single crystals in a liquid encapsulated Czochralski process

Life of this patent

Abstract

Claims26