Laser irradiation aluminum doping for monocrystalline silicon substrates

Patent metadata

Field	Value
Publication number	US-9455362-B2
Application number	US-201113340903-A
Country	US
Kind code	B2
Filing date	Dec 30, 2011
Priority date	Oct 6, 2007
Publication date	Sep 27, 2016
Grant date	Sep 27, 2016

Abstract

Methods for laser irradiation aluminum doping for monocrystalline silicon substrates are provided. According to one aspect of the disclosed subject matter, aluminum metal contacts are formed directly on a surface of a monocrystalline silicon substrate. The aluminum metal contact is selectively heated via laser irradiation, thereby causing the aluminum and a portion of the monocrystalline silicon substrate in proximity to the aluminum to reach a temperature sufficient to allow at least a portion of the silicon to dissolve in the aluminum. The aluminum and the portion of the monocrystalline silicon substrate in proximity to the aluminum is allowed to cool, thereby forming an aluminum-rich doped silicon layer on the monocrystalline silicon substrate.

First claim

What is claimed is:

1. A method for making an aluminum doped p-type region in a silicon substrate, said method comprising:
forming an aluminum metal contact directly on a surface of a monocrystalline silicon substrate;
selectively heating said aluminum metal contact via laser irradiation, thereby causing said aluminum and a portion of said monocrystalline silicon substrate in proximity to said aluminum to reach a temperature sufficient to allow at least a portion of said silicon to dissolve in said aluminum; and
allowing said aluminum and said portion of said monocrystalline silicon substrate in proximity to said aluminum to cool, thereby forming an aluminum-rich doped silicon layer on said monocrystalline silicon substrate.

2. The method of claim 1 , wherein said monocrystalline silicon substrate comprises an epitaxial silicon substrate.

3. The method of claim 1 , wherein said temperature comprises at least approximately 577° C. for a eutectic aluminum-silicon melt formation.

4. A method for making a doped p-type selective emitter in a back-contact/back-junction solar cell, said method comprising:
forming an emitter region on a surface of a monocrystalline silicon substrate having n-type base doping, said emitter region having p-type doping;
forming an aluminum metal contact directly on said emitter region;
selectively heating said aluminum metal contact via laser irradiation, thereby causing said aluminum and a portion of said emitter region in proximity to said aluminum to reach a temperature sufficient to allow at least a portion of said silicon to dissolve in said aluminum; and
allowing said aluminum and said portion of said emitter region in proximity to said aluminum to cool, thereby creating a doped selective emitter region.

5. The method of claim 4 , wherein said monocrystalline silicon substrate is an epitaxial silicon substrate.

6. The method of claim 4 , wherein said temperature comprises at least approximately 577° C. for a eutectic aluminum-silicon melt formation.

7. A method for making an aluminum doped region in a front-contact solar cell, said method comprising:
forming an aluminum metal contact directly on a back side of a monocrystalline silicon substrate having a first doping type;
selectively heating said aluminum metal contact via laser irradiation, thereby causing said aluminum and a portion of said silicon in proximity to said aluminum to reach a temperature sufficient to allow at least a portion of said silicon to dissolve in said aluminum; and
allowing said aluminum and said portion of said silicon in proximity to said aluminum to cool, thereby creating an aluminum doped region on said back side of said monocrystalline silicon substrate.

8. The method of claim 7 , wherein said monocrystalline silicon substrate is an epitaxial silicon substrate.

9. The method of claim 7 , wherein said temperature comprises at least approximately 577° C. for a eutectic aluminum-silicon melt formation.

10. The method of claim 7 , wherein:
said first doping type comprises n-type doping; and further wherein
said portion of said silicon in proximity to said aluminum comprises a doped emitter region; and further wherein
said aluminum doped region comprises a selective emitter region.

11. The method of claim 7 , wherein:
said first doping type comprises p-type doping; and further wherein
said aluminum doped region comprises a back-surface field region.

12. The method of claim 1 , wherein said laser comprises either a continuous wave laser or a pulsed laser having pulse length greater than approximately 10 nanoseconds.

13. The method of claim 4 , wherein said laser comprises either a continuous wave laser or a pulsed laser having pulse length greater than approximately 10 nanoseconds.

14. The method of claim 7 , wherein said laser comprises either a continuous wave laser or a pulsed laser having pulse length greater than approximately 10 nanoseconds.

15. The method of claim 1 , wherein said laser has a wavelength of approximately 10.6 micrometers or less.

16. The method of claim 4 , wherein said laser has a wavelength of approximately 10.6 micrometers or less.

17. The method of claim 7 , wherein said laser has a wavelength of approximately 10.6 micrometers or less.

18. The method of claim 5 , wherein said epitaxial thin film solar cell has a thickness in the range of approximately 10 to 100 microns.

19. The method of claim 18 , wherein a front surface of said epitaxial thin film comprises three-dimensional pyramids or prisms formed via a textured template liftoff process.

20. The method of claim 18 , wherein said epitaxial thin film comprises a substantially planar epitaxial film formed via an epitaxial silicon liftoff process.

21. The method of claim 8 , wherein said epitaxial thin film solar cell has a thickness in the range of approximately 10 to 100 microns.

22. The method of claim 21 , wherein a front surface of said epitaxial thin film comprises three-dimensional pyramids or prisms formed via a textured template liftoff process.

23. The method of claim 21 , wherein said epitaxial thin film comprises a substantially planar epitaxial film formed via an epitaxial silicon liftoff process.

Assignees

• Moslehi Mehrdad M
• Rana Virendra V
• Anbalagan Pranav
• Solexel Inc

Inventors

• Moslehi Mehrdad M
• Rana Virendra V
• Anbalagan Pranav

Classifications

• H10P34/42

  with electromagnetic radiation, e.g. laser annealing (laser cutting H10P54/20) · CPC title

• H10P32/1408

  from or through or into an external applied layer, e.g. photoresist or nitride layers · CPC title

• H10P32/171

  being group IV material · CPC title

• H10F77/703

  of the semiconductor bodies, e.g. textured active layers · CPC title

• H10F77/219

  Arrangements for electrodes of back-contact photovoltaic cells · CPC title