WORKPIECE PATTERNING WITH PLASMA SHEATH MODULATION

• US 20110151610A1
• Filed: 12/23/2009
• Published: 06/23/2011
• Est. Priority Date: 12/23/2009
• Status: Active Grant

• Current Assignee: Varian Semiconductor Equipment Associates Incorporated (Applied Materials Incorporated)
• Original Assignee: Varian Semiconductor Equipment Associates Incorporated (Applied Materials Incorporated)
• Inventors: RAMAPPA, Deepak A., Godet, Ludovic
• Granted Patent: US 8,187,979 B2
• Time in Patent Office: Days
• US Class Current: 438/57
• CPC Class Codes: H01J 37/32366 Localised processing
• CPC Class Codes: H01J 37/32422 Arrangement for selecting ions or species in the plasma
• CPC Class Codes: H01J 37/32623 Mechanical discharge control means
• CPC Class Codes: H01L 21/3065 Plasma etching; Reactive-ion etching
• CPC Class Codes: H01L 31/068 the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar 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

Abstract

Methods to texture or fabricate workpieces are disclosed. The workpiece may be, for example, a solar cell. This texturing may involve etching or localized sputtering using a plasma where a shape of a boundary between the plasma and the plasma sheath is modified with an insulating modifier. The workpiece may be rotated in between etching or sputtering steps to form pyramids. Regions of the workpiece also may be etched or sputtered with ions formed from a plasma adjusted by an insulating modifier and doped. A metal layer may be formed on these doped regions.

Claims

1. A method to process a workpiece comprising:

generating a plasma having a plasma sheath proximate a surface of said workpiece;

controlling a shape of a boundary between said plasma and said plasma sheath whereby a portion of said shape is not parallel to said surface of said workpiece;

removing a first portion of said surface of said workpiece with said plasma, said surface parallel to a plane;

rotating said workpiece in a direction parallel to said plane; and

removing a second portion of said surface of said workpiece with said plasma.

2. The method of claim 1, wherein said workpiece defines a v-shaped groove after said removing said first portion and wherein said workpiece defines a pyramid-shaped groove after said removing said second portion.

3. The method of claim 1, wherein said workpiece is a solar cell.

4. The method of claim 1, wherein said workpiece comprises Si.

5. The method of claim 1, wherein said removing said first portion and said removing said second portion are performed using a species selected from the group consisting of a noble gas, H, N, and F.

6. The method of claim 1, wherein said rotating comprising translating said workpiece 90°

.

7. The method of claim 1, wherein ions formed from said plasma have a focus, said focus being either between said plasma sheath and said surface of said workpiece or below said surface of said workpiece.

8. A method to fabricate a workpiece comprising:

generating a plasma having a plasma sheath proximate a surface of said workpiece;

controlling a shape of a boundary between said plasma and said plasma sheath whereby a portion of said shape is not parallel to said surface of said workpiece;

removing a region of said surface of said workpiece with said plasma; and

doping said region of said workpiece.

9. The method of claim 8, wherein said workpiece is a solar cell.

10. The method of claim 9, wherein said solar cell has an oxide layer and an anti-reflective coating on said surface and said removing etches through or sputters off said oxide layer and said anti-reflective coating over said region of said surface.

11. The method of claim 8, wherein said removing and said doping are at least partially simultaneous.

12. The method of claim 11, wherein said removing and said doping use a first species selected from the group consisting of B and P and a second species selected from the group consisting of He and F.

13. The method of claim 8, wherein said removing is performed using a species selected from the group consisting of a noble gas, H, N, and F.

14. A method to fabricate a solar cell comprising:

texturing at least a first region of a surface of said solar cell;

implanting said surface of said solar cell with a dopant;

removing at least one second region of said surface of said solar cell with a plasma having a plasma sheath by generating said plasma and controlling a shape of a boundary between said plasma and said plasma sheath whereby a portion of said shape is not parallel to said surface of said solar cell;

doping said second region of said solar cell; and

forming a metal layer on said second region.

15. The method of claim 14, wherein said texturing comprises chemical etching, plasma etching, laser texturing, or using a plasma wherein a shape of a boundary between said plasma and a plasma sheath is modified whereby a portion of said shape is not parallel to said surface of said solar cell.

16. The method of claim 14, further comprising depositing an anti-reflective coating and forming an oxide layer on said surface of said solar cell.

17. The method of claim 16, wherein said removing said at least one second region removes said anti-reflective coating and said oxide layer over said at least one second region.

18. The method of claim 14, wherein said implanting forms a first doped region in said solar cell and wherein said removing said at least one second region removes said first doped region in said at least one second region.

19. The method of claim 14, wherein said removing is performed using a species selected from the group consisting of a noble gas, H, N, and F.