Methods and apparatus for producing coherent or monolithic elements
OwnerMilton Stollinventor
Life of this patent
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Abstract
Methods and apparatus for producing coherent or monolithic elements, such as mono-crystalline semi-conductor rods, preferably by growing or drawing one or more such elements upwardly from an off-center portion of a molten pool in the top of a cake of material while rotating the cake and/or rod or rods, for example, in the same direction and at the same rate; heat balancing the element as it is grown from the pool and maintaining the rod-pool location positioned relative to heating means, as by adding additional materials to the pool as the element is withdrawn; and/or providing relative feeding movement between the cake and rod; and providing a chilled mold beneath the cake.
Claims18
Method of forming crystalline material into large diameter substantially mono-crystalline rods having a minimum of dislocations comprising, at least the steps of, rotating a substantially solid cake of crystalline material within a controlled atmosphere about a generally vertical central axis;
- heating at least a portion of the upper surface of such cake on at least one side of the rotational axis to a temperature just above the melting point of the material so that the heat and rotation provide a pool of molten material encircling the rotational axis supported and contained by the cake;
- slowly withdrawing a substantially mono-crystalline rod upwardly from the surface of said pool so that material from said pool may crystallize at the interface therebetween to elongate the crystal structure of the rod;
- and rotating the rod at substantially the same rotational velocity and in the same direction about a generally vertically disposed axis parallel to and off-center from the rotational axis of the cake so that the relative motion at the pool-rod interface is substantially uniform across the entire face of the rod and thermal asymmetrics are minimized.
In a method of forming crystalline materials into substantially mono-crystalline rods wherein a pool of molten crystalline material is rotated about a generally vertical axis, and a substantially monocrystalline rod is withdrawn upwardly from the surface of the pool so that material from the pool crystallizes at the interface therebetween to elongate the crystal structure of the rod, the improvement comprises:
- providing a controlled temperature zone at the interface between the pool and the rod;
- and
- controlling the temperature of the controlled temperature zone so that as the rod is passed through the controlled temperaure zone, the horizontal cross sectional growing profile across the rod at the rod-pool interface is controlled to maintain a uniform temperature across said horizontal cross sectional growing profile.
In a method of forming crystalline materials into substantially monocrystalline rods wherein said rod is withdrawn from a molten pool so that the material from the pool crystallizes at the interface therebetween to elongate the crystal structure of the rod, the improvement comprises:
- providing a controlled temperature zone at the interface between the pool and the rod;
- and
- controlling the temperature of the controlled temperature zone so that as the rod is passed through the controlled temperature zone at a fixed distance from the pool, the temperature profile horizontally across the cross-section of the rod at the rod-pool interface is uniformly controlled to maintain a uniform temperature across said horizontal cross section of the rod.
Method of forming crystalline material into large diameter substantially mono-crystalline rods having a minimum of dislocations comprising, at least the steps of, rotating a substantially solid cake or crystalline material within a controlled atmosphere about a generally vertical central axis;
- heating such cake to maintain the temperature thereof just below the melting point of the materia;
- heating at least a portion of the upper surface of such cake on at least one side of the rotational axis to a temperature just above the melting point of the material so that the heat and rotation provide a pool of molten material having a generally uniform temperature supported and contained by the cake;
- slowly withdrawing a substantially monocrystalline rod upwardly from the surface of said pool so that material from said pool may crystallize at the interface therebetween to elongate the crystal structure of the rod;
- and providing a uniform and controlled temperature zone to the rod at a fixed distance from the surface of the pool so that a flat and uniform temperaure will exist horizontally across the cross section of the interface.
Dependencies are inferred from the claim text.