Claims
- 1. In a process in which a ribbon of crystal is grown from a body of melt at a growth interface, with string stabilization being employed at the edges of said ribbon, a method for minimizing the introduction of impurities from said melt to said crystal grown therefrom comprising: reducing build-up of impurities in the body of the melt due to impurity segregation at the growth interface during crystal growth by continually replenishing the melt with new raw material, and dumping and completely removing a fraction of molten material from said body of melt continually during the crystal growth process, said fraction being removed at a rate less than the rate of addition of new raw material such that the concentration of impurities in said body of melt and therefore in the growth crystal is reduced during crystal growth, in an open loop process.
- 2. The method of claim 1 wherein said dumping is accomplished by confining the melt to a crucible, providing the crucible with an outlet port from which melt is to flow, and providing an electromagnetically generated force on the melt at the output port which acts to counteract the flow at the outlet port.
- 3. The method of claim 1 wherein the melt is confined to a crucible, wherein the crucible is provided with an outlet port from which melt is to flow, and wherein means are provided to alternately freeze and thaw the material at the outlet port, thereby to control the dumping.
- 4. The method of claim 1 wherein said fraction of molten material dumped and removed from the melt is such that the mass of melt so removed per unit time is less than the mass of growing crystal per unit time.
- 5. A method for minimizing the introduction of impurities into a ribbon of crystalline material formed, with the aid of strings to stabilize the edges of said ribbon, in a crystal-growing process from a melt at a growth interface located at the melt surface, comprising the following steps:
- maintaining a flow of melt in the vicinity of the growth interface, to disperse and remove from the growth interface impurities left at said interface during said crystal growing process;
- dumping and discarding impurity-containing melt material continually from the body of said melt; and
- continually replenishing with fresh melt material the melt material removed from the body of the melt by said dumping step and by said crystal growing process;
- said dumping and replenishing steps serving to continually reduce the concentration of impurities in said melt, reducing impurity build-up in the melt as a result of impurity segregation during crystal growth.
- 6. The method of claim 5 wherein the step of maintaining a flow of melt is accomplished by inducing electromagnetic forces in said melt.
- 7. The method of claim 5 wherein said dumping step is accomplished by confining said melt to a crucible, providing said crucible with an outlet port having its inlet below the level of said melt, and controlling the flow of melt material through said outlet port by inducing electromagnetic forces in the melt to counteract the gravitational force.
- 8. The method of claim 5 wherein said dumping step is accomplished by confining said melt to a crucible, providing said crucible with an outlet port having its inlet below the level of said melt, and controlling the flow of melt material through said outlet port by alternately freezing and thawing the material at the outlet port.
RELATED APPLICATION
This is a continuation of application Ser. No. 214,741, filed Dec. 11, 1980, now abandoned, which is a continuation-in-part of application Ser. No. 109,865 filed Jan. 7, 1980, now abandoned, which application was entitled "String Stabilized Ribbon Growth.
US Referenced Citations (3)
Continuations (1)
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214741 |
Dec 1980 |
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Continuation in Parts (1)
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109865 |
Jan 1980 |
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