METHOD OF DYNAMIC TEMPERATURE CONTROL DURING MICROCRYSTALLINE SI GROWTH

• US 20090105873A1
• Filed: 10/22/2007
• Published: 04/23/2009
• Est. Priority Date: 10/22/2007
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: CHAE, YONG KEE, CHOI, SOO YOUNG
• Granted Patent: US 7,687,300 B2
• Time in Patent Office: Days
• US Class Current: 700/207
• CPC Class Codes: C23C 16/24 Deposition of silicon only
• CPC Class Codes: C23C 16/46 characterised by the method used for heating the substrate C23C16/48, C23C16/50 take precedence
• CPC Class Codes: H01L 31/1824 Special manufacturing methods for microcrystalline Si, uc-Si
• CPC Class Codes: Y02E 10/545 Microcrystalline silicon PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

The present invention generally comprises a method for dynamically controlling the temperature of a solar cell substrate during microcrystalline silicon deposition. In amorphous silicon/microcrystalline tandem solar cells, microcrystalline silicon may be deposited using a higher power density and to a greater thickness than amorphous silicon. The higher the power density applied, the faster the deposition may occur, but the temperature of the deposition may also increase. At high temperatures, the likelihood of dopant diffusing into the intrinsic layer of the solar cell and damaging the cell is greater. By dynamically controlling the temperature of the susceptor, the substrate and hence, the dopant can be maintained at a substantially constant temperature below the value at which the dopant may diffuse into the intrinsic layer. The dynamic temperature control permits the microcrystalline silicon to be deposited at a high power density without damaging the solar cell.

Claims

1. A solar cell formation method, comprising:

maintaining a substrate at a substantially constant temperature while dynamically controlling the temperature of a susceptor upon which the substrate is disposed, the dynamically controlling sequentially consisting essentially of;

heating the susceptor for a first period of time;

simultaneously heating the susceptor and cooling the susceptor for a second period of time; and

cooling the susceptor for a third period of time.

2. The method of claim 1, wherein the dynamically controlling the temperature occurs during deposition of a microcrystalline silicon layer.

3. The method of claim 1, wherein the third period of time is greater than the first period of time.

4. The method of claim 1, wherein the simultaneously heating the susceptor and cooling the susceptor comprises:

reducing a heating output to the susceptor; and

increasing a cooling output to the susceptor.

5. The method of claim 1, wherein the substantially constant temperature of the substrate is between about 160 degrees Celsius and about 220 degrees Celsius.

6. The method of claim 1, further comprising:

providing real time substrate temperature measurements to a controller; and

dynamically controlling the temperature of the susceptor in response to the measurements.

7. The method of claim 1, further comprising:

forming a top p-i-n junction comprising a first p-doped layer, an amorphous silicon layer, and a first n-doped layer; and

forming a bottom p-i-n junction comprising a second p-doped layer, a microcrystalline silicon layer, and a second n-doped layer, wherein the maintaining and the dynamically controlling occur during the forming of the microcrystalline silicon layer.

8. A solar cell formation method, comprising:

depositing a silicon layer over a substrate disposed on a susceptor while maintaining the substrate at a substantially constant temperature and varying the temperature of the susceptor.

9. The method of claim 8, further comprising:

forming a top p-i-n junction comprising;

depositing a first p-doped layer over the substrate;

depositing an amorphous silicon layer over the first p-doped layer to a first thickness at a first power density; and

depositing a first n-doped layer over the amorphous silicon layer; and

forming a bottom p-i-n junction comprising;

depositing a second p-doped layer over the first n-doped layer;

depositing a microcrystalline silicon layer over the second p-doped layer to a second thickness at a second power density while maintaining the substrate at a substantially constant temperature and varying the temperature of the susceptor; and

depositing a second n-doped layer over the microcrystalline silicon layer.

10. The method of claim 9, wherein a ratio of the second power density to the first power density is about 10:

1.

11. The method of claim 8, wherein varying the temperature of the susceptor sequentially consists essentially of:

heating the susceptor for a first period of time;

simultaneously heating the susceptor and cooling the susceptor for a second period of time; and

cooling the susceptor for a third period of time.

12. The method of claim 11, wherein the simultaneous heating and cooling comprises:

reducing a heating output to the susceptor; and

increasing a cooling output to the susceptor.

13. The method of claim 11, wherein the third period of time is greater than the first period of time and the first period of time is greater than the second period of time.

14. The method of claim 8, further comprising:

providing real time substrate temperature measurements to a controller; and

varying the temperature of the susceptor based upon the measurements.

15. The method of claim 8, wherein the substantially constant temperature of the substrate is between about 180 degrees Celsius and about 220 degrees Celsius.

16. A solar cell formation method, comprising:

heating a susceptor to a first temperature by providing a heat output to the susceptor;

reducing the heat output to the susceptor to lower the temperature of the susceptor to a second temperature;

reducing the heat output to the susceptor while increasing a cooling output to the susceptor to lower the temperature of the susceptor to a third temperature; and

providing a substantially constant cooling output to the susceptor to substantially maintain the susceptor at the third temperature.

17. The method of claim 16, wherein the cooling output is substantially zero during the reducing to the second temperature.

18. The method of claim 16, wherein the heating output is substantially zero during the providing a substantially constant cooling output.

19. The method of claim 16, wherein a substrate disposed on the susceptor maintains a substantially constant temperature during the heating, reducing, and providing substantially constant cooling.

20. The method of claim 16, further comprising:

depositing a microcrystalline silicon layer over a substrate disposed on the susceptor.

21. The method of claim 20, wherein the microcrystalline silicon layer is deposited over an amorphous silicon layer deposited over the substrate.