Method of making thin silicon sheets for solar cells

• US 7,169,669 B2
• Filed: 12/04/2002
• Issued: 01/30/2007
• Est. Priority Date: 12/04/2001
• Status: Expired due to Fees

• Current Assignee: Australian National University
• Original Assignee: Origin Energy SA Pty Limited (Origin Energy Limited)
• Inventors: Blakers, Andrew William, Weber, Klaus Johannes
• Primary Examiner(s): Dang; Phuc T.
• Application Number:
  US10/497,369
• Publication Number:
  US 20050070059A1
• Time in Patent Office: 1,518 Days
• Field of Search: 438/258, 438/696, 438/704, 438/705, 438/706
• US Class Current: 438/258
• CPC Class Codes: C30B 29/06 Silicon
• CPC Class Codes: C30B 33/00 After-treatment of single crystals or homogeneous polycrystalline material with defined structure C30B31/00 takes precedence
• CPC Class Codes: H01L 21/30608 Anisotropic liquid etching H01L21/3063 takes precedence
• CPC Class Codes: H01L 31/022425 for solar cells
• CPC Class Codes: H01L 31/022441 Electrode arrangements specially adapted for back-contact solar cells
• CPC Class Codes: H01L 31/0516 specially adapted for interconnection of back-contact solar cells
• CPC Class Codes: H01L 31/0682 back-junction, i.e. rearside emitter, solar cells, e.g. interdigitated base-emitter regions back-junction cells
• CPC Class Codes: H01L 31/1804 comprising only elements of Group IV of the Periodic Table
• CPC Class Codes: Y02E 10/547 Monocrystalline silicon PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y10T 428/2457 Parallel ribs and/or grooves

Abstract

A thin layer of single-crystal silicon is produced by forming first trenches in a silicon substrate having (111) orientation; forming narrower second trenches at the bases of the trenches; anisotropically etching lateral channels (4) from the second trenches, until adjacent etch fronts (16) substantially meet; and detaching said layer from the substrate. The trenches may be arranged so that the resultant layer has rows of slots, whit the slots in adjacent rows being mutually offset. Solar cells may be formed on strips (5) between the trenches, having lengths of more than 50 mm, widths of up to 5 mm, and thicknesses of less than 100 microns, and having two electrical contacts on the same face (6) of each strip (5).

Claims

1. A process for producing a layer of single-crystal silicon, said process comprising the steps of forming parallel, first trenches in a silicon substrate of substantially (111) orientation;

applying an etch-resistant layer to the surface of said first trenches;

forming a series of narrower second trenches inside said first trenches;

contacting said second trenches with an etchant to which {111} planes of silicon are substantially resistant, and etching lateral channels from said second trenches until adjacent and opposing etch fronts at least substantially meet, thereby defining said layer of single-crystal silicon; and

detaching said layer from said substrate.

2. A process according to claim 1 wherein said first and second trenches extend continuously from one edge of said silicon substrate to an opposite edge of said silicon substrate.

3. A process according to claim 1 wherein said first and second trenches do not extend as far as at least one edge of said silicon substrate.

4. A process according to claim 3 where said first and second trenches do not extend to any edge of said silicon substrate.

5. A process according to claim 1 wherein said adjacent and opposing etch fronts meet.

6. A process according to claim 1 wherein said layer of single-crystal silicon comprises a plurality of strips of silicon.

7. A process according to claim 6 where said strips are attached to said layer at least at one end of said strips, said process further comprising the step of separating said strips from said layer of silicon.

8. A process according to claim 6 or claim 7 further comprising the steps of forming a plurality of solar cells from said plurality of strips before or after said strips are separated.

9. A solar cell prepared by the process of claim 8.