APPARATUS FOR PURIFYING METALLURGICAL SILICON FOR SOLAR CELLS

• US 20110198336A1
• Filed: 02/08/2011
• Published: 08/18/2011
• Est. Priority Date: 02/12/2010
• Status: Active Grant

• Current Assignee: Cheng C. Kao, Masahiro Hoshino
• Original Assignee: Cheng C. Kao, Masahiro Hoshino
• Inventors: Hoshino, Masahiro, Kao, Cheng C.
• Granted Patent: US 8,461,487 B2
• Time in Patent Office: Days
• US Class Current: 219/383
• CPC Class Codes: C01B 33/037 Purification by zone-melting C30B13/00
• CPC Class Codes: C30B 11/002 Crucibles or containers for supporting the melt
• CPC Class Codes: C30B 11/003 Heating or cooling of the melt or the crystallised material
• CPC Class Codes: C30B 29/06 Silicon
• CPC Class Codes: F27B 14/06 heated electrically, e.g. induction crucible furnaces with or without any other source of heat F27B14/04 takes precedence
• CPC Class Codes: F27B 14/14 Arrangements of heating devices
• CPC Class Codes: H05B 7/18 Heating by arc discharge
• CPC Class Codes: Y02E 10/546 Polycrystalline silicon PV cells

Abstract

A system for forming high quality silicon material, e.g., polysilicon. In a specific embodiment, the melted material comprises a silicon material and an impurity, e.g., phosphorous species. The system includes a crucible having an interior region. In a specific embodiment, the crucible is made of a suitable material such as a quartz material or others. The quartz material is capable of withstanding a temperature of at least 1400 Degrees Celsius for processing silicon. In a specific embodiment, the crucible is configured in an upright position and has an open region to expose a melted material. In a specific embodiment, the present system has an energy source. Such energy source may be an arc heater or other suitable heating device, including multiple heating devices, which may be the same or different. The arc heater is configured above the open region and spaced by a gap between the exposed melted material and a muzzle region of the arc heater to cause formation of a determined temperature profile within a vicinity of a center region of the exposed melted material while maintaining outer regions of the melted material at a temperature below a melting point of the quartz material of the crucible. In a specific embodiment, the system produces a melted material comprising a resulting phosphorous species of 0.1 ppm and less, which is purified silicon.

Claims

1. A system for forming high quality silicon material for photovoltaic devices, the system comprising:

a crucible having an interior region, the crucible being made of a quartz material, the quartz material being capable of withstanding a temperature of at least 1400 Degrees Celsius, the crucible being configured in an upright position and having an open region to expose a melted material; and

an energy source comprising an arc heater configured above the open region and spaced by a gap between the exposed melted material and a muzzle region of the arc heater to cause formation of a determined temperature profile within a vicinity of a center region of the exposed melted material while maintaining outer regions of the melted material at a temperature below a melting point of the quartz material of the crucible.

2. The system of claim 1 wherein the arc heater is a plasma gun configured to emit an excited argon species to cause thermal transfer to a portion of the melted material, the arc heater being configured with a thermal transfer device to cause cooling of the arc heater.

3. The system of claim 1 wherein the arc heater is capable of being ignited by a source.

4. The system of claim 1 wherein the arc heater comprises a power rating of 20 kWatt and greater and capable of being pulsed according to a duty cycle.

5. The system of claim 1 wherein the muzzle region has a maximum dimension of about 0.5 centimeters to about 2 centimeters.

6. The system of claim 1 wherein the maximum temperature profile is greater than about 3000 Degrees to cause removal of phosphorous entities from the melted material.

7. The system of claim 1 wherein the melted material comprises convective flow caused by a temperature gradient formed by at least the maximum temperature profile.

8. The system of claim 7 wherein the convective flow causes a mixing within the melted material.

16. The system of claim 1 wherein the crucible being subject to a cover gas to maintain the melted material within the crucible.

17. The system of claim 1 wherein the crucible being subject to an argon containing cover gas to maintain the melted material within the crucible, the cover gas being suitable to maintain the melted material free from oxidation.

18. The system of claim 1 further comprising a carrier gas configured to cause a portion of evaporated melted material to return to the melted material.

19. The system of claim 1 further comprising a plurality of surface regions configured to cause a substantial portion of a phosphorus species to be exhausted while returning a substantial portion of silicon species into the melted material.

20. The system of claim 1 further comprising a plurality of fin regions configured to cause a substantial portion of a phosphorus species to be exhausted while returning a substantial portion of silicon species into the melted material;

wherein the melted material comprises a silicon material and a phosphorous species; and

wherein the melted material comprises a resulting phosphorous species of 0.1 ppm and less.

9. A system for forming high quality silicon material for solar cells, the system comprising:

a crucible having an interior region, the crucible being made of a quartz material, the quartz material being capable of withstanding a temperature of at least 1400 Degrees Celsius, the crucible being configured in an upright position and having an open region to expose a melted material;

an energy source comprising an arc heater configured above the open region and spaced by a gap between the exposed melted material and a muzzle region of the arc heater to cause formation of a determined temperature profile within a vicinity of a center region of the exposed melted material while maintaining outer regions of the melted material at a temperature below a melting point of the quartz material of the crucible; and

a nozzle region configured to output argon gas to cause a dimple region within a vicinity of the center region of the melted material.

10. The system of claim 9 wherein the argon gas comprises a flow rate suitable to form the dimple region comprising a plurality of recessed regions each of which is separated by an elevated region.

11. The system of claim 9 wherein the nozzle region is coupled to an argon gas source, the nozzle region comprising a ceramic material.

12. The system of claim 11 wherein the argon gas source is operable independent from the arc tube;

wherein the melted material comprises a viscosity of 0.7 Pascal-second; and

wherein the argon gas source is 99.99% purity and greater.

13. The system of claim 9 wherein the dimple region provides an increased surface region for a plume to interact with the melted material;

wherein the dimple region has a depth of at least one centimeter and greater.

14. The system of claim 13 wherein the increased surface region is at least three times greater than a surface region without the dimple region.

15. The system of claim 13 wherein the increased surface region is at least five times greater than a surface region without the dimple region;

wherein the melted material is characterized by a turbulent flow; and

wherein the arc heater is configured to subject a selected portion of the exposed region of the melted material.