Methods for printing an ink on a textured wafer surface

• US 8,247,312 B2
• Filed: 04/24/2008
• Issued: 08/21/2012
• Est. Priority Date: 04/24/2008
• Status: Expired due to Fees

• Current Assignee: Innovalight, Inc. (Corteva, Inc.)
• Original Assignee: Innovalight, Inc. (Corteva, Inc.)
• Inventors: Abbott, Malcolm, Kelman, Maxim, Vanheusden, Karel
• Primary Examiner(s): TRINH, MICHAEL MANH
• Application Number:
  US12/108,888
• Publication Number:
  US 20090325336A1
• Time in Patent Office: 1,580 Days
• Field of Search: 438/497, 438/498, 438/478, 438/479, 438/584, 257/E21.586
• US Class Current: 438/478
• CPC Class Codes: H01L 21/0243 Surface structure
• CPC Class Codes: H01L 21/02532 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/02601 Nanoparticles fullerenes H10K85/211
• CPC Class Codes: H01L 21/02628 using solutions
• CPC Class Codes: H01L 21/228 using diffusion into or out of a solid from or into a liquid phase, e.g. alloy diffusion processes H01L21/221 - H01L21/222 take precedence
• CPC Class Codes: H01L 29/34 the imperfections being on the surface
• CPC Class Codes: H01L 31/02168 the coatings being antireflective or having enhancing optical properties for the solar cells
• CPC Class Codes: H01L 31/02363 of the semiconductor body itself, e.g. textured active layers
• 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

Abstract

A method of printing an ink on a wafer surface configured with a set of non-rounded peaks and a set of non-rounded valleys is disclosed. The method includes exposing the wafer including at least some non-rounded peaks and at least some of the non-rounded valleys in a region to an etchant. The method further includes depositing the ink on the region, wherein a set of rounded peaks and a set of rounded valleys are formed.

Claims

1. A method of coating a silicon wafer with an ink, the silicon wafer including a surface with a set of non-rounded peaks and a set of non-rounded valleys, wherein each non-rounded peak of the set of non-rounded peaks includes a first apex surface area, wherein each non-rounded valley of the set of non-rounded valleys is defined between two proximally located non-rounded peaks, and wherein each non-rounded valley further includes a first valley surface area, comprising,

adding an etch mask to the surface of the silicon wafer with the set of non-rounded peaks and the set of non-rounded valleys,

exposing the silicon wafer including at least some of the non-rounded peaks and at least some of the non-rounded valleys in a region to an etchant while the non-rounded peaks and the non-rounded valleys outside the region is not exposed to the etchant, wherein a set of rounded peaks and a set of rounded valleys are formed in the region, each rounded peak of the set of rounded peaks having a second apex surface area smaller than the first apex surface area, each rounded valley of the set of the rounded valleys having a second valley surface area smaller than the first valley surface area, thereby obtaining the silicon wafer including the rounded peaks and the rounded valleys in the region and the non-rounded peaks and the non-rounded valleys outside the region;

and,

depositing the ink on the region.

2. The method of claim 1, wherein the non-rounded peaks have a pyramid shape.

3. The method of claim 1, wherein the etch mask is one of a hot melt wax or a UV curable polymer.

4. The method of claim 1, where the ink is a nanoparticle ink, the nanoparticle ink including a set of Group IV semiconductor particles and a solvent.

5. The method of claim 4, wherein after the step of depositing the ink on the region, further including the steps of:

heating the nanoparticle ink to a first temperature and for a first time period to form a non-densified thin film;

heating the non-densified thin film to a second temperature and for a second time period to form a densified thin film.

6. The method of claim 5, wherein the first temperature is from about 30°

C. to about 300°

C., and the first time period is from about 1 minute to about 60 minutes.

7. The method of claim 6, wherein the second temperature is from about 100°

C. to about 1000°

C., and the second time period is from about 5 seconds to about 10 hours.

8. The method of claim 1, wherein the etchant includes an HNO₃ etchant and a HF etchant.

9. The method of claim 8, wherein a ratio of the HNO₃ etchant to the HF etchant is about 1 to about 19.

10. The method of claim 9, wherein the etchant is applied for about 2 minutes.

11. The method of claim 1, wherein the silicon wafer is a crystalline silicon wafer for a solar cell.

12. The method of claim 1, wherein said depositing deposits the ink on the region uniformly.