USE OF ION BEAM TAILS TO MANUFACTURE A WORKPIECE

• US 20130008494A1
• Filed: 07/07/2011
• Published: 01/10/2013
• Est. Priority Date: 07/07/2011
• Status: Active Grant

• Current Assignee: Varian Semiconductor Equipment Associates Incorporated (Applied Materials Incorporated)
• Original Assignee: Varian Semiconductor Equipment Associates Incorporated (Applied Materials Incorporated)
• Inventors: Bateman, Nicholas P.T., Riordon, Benjamin B., Graff, John W., Kurunczi, Peter L.
• Granted Patent: US 8,697,559 B2
• Time in Patent Office: Days
• US Class Current: 136/255
• CPC Class Codes: H01J 2237/31711 using mask
• CPC Class Codes: H01L 21/26513 of electrically active species
• CPC Class Codes: H01L 21/26586 characterised by the angle between the ion beam and the crystal planes or the main crystal surface
• CPC Class Codes: H01L 21/266 using masks H01L21/26586 takes precedence
• CPC Class Codes: H01L 31/022441 Electrode arrangements specially adapted for 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 31/0687 Multiple junction or tandem solar cells
• CPC Class Codes: H01L 31/18 Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
• CPC Class Codes: H01L 31/1804 comprising only elements of Group IV of the Periodic Table
• CPC Class Codes: Y02E 10/544 Solar cells from Group III-V materials
• 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

One method of implanting a workpiece involves implanting the workiece with an n-type dopant in a first region with center and a periphery. The workpiece also is implanted with a p-type dopant in a second region complementary to the first region. This second region also has a center and a periphery. The periphery of the first region and the periphery of the second region at least partially overlap. A dose at the periphery of the first region or second region is less than a dose at the center of the first region or second region. The region of overlap may function as a junction where charge carriers cannot pass.

Claims

1. A method of implanting a workpiece comprising:

implanting said workiece with an n-type dopant in a first region, said first region having a center and a periphery; and

implanting said workpiece with a p-type dopant in a second region complementary to said first region, said second region having a center and a periphery, wherein said periphery of said first region and said periphery of said second region at least partially overlap and wherein a dose at said periphery of said first region is less than a dose at said center of said first region and a dose at said periphery of said second region is less than a dose at said center of said second region.

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

3. The method of claim 1, wherein said implanting said n-type dopant and said p-type dopant each comprises implanting through a mask disposed a distance from said workpiece, said mask defining at least one aperture.

4. The method of claim 3, further comprising determining a desired dose at said periphery of said first region and said periphery of said second region, and further comprising adjusting a distance between said mask and said workpiece to implant said desired dose at said periphery of said first region and said periphery of said second region.

5. The method of claim 1, wherein at least one of said implanting said n-type dopant and said p-type dopant comprises focusing said n-type dopant and said p-type dopant during said implanting.

6. The method of claim 1, wherein at least one of said implanting with said p-type dopant and said implanting with said n-type dopant is performed at an angle with respect to a surface of said workpiece.

7. The method of claim 1, further comprising adjusting an angle distribution of at least one of said n-type dopant and said p-type dopant, said adjusting configured to change a lateral dose profile for said first region or said second region.

8. The method of claim 1, further comprising implanting said workpiece with either an n-type dopant or a p-type dopant to form a third region, said third region encompassing said first region and said second region, said first region and said second region extending to a depth deeper than said third region.

9. A method of implanting a workpiece comprising:

implanting an entire surface of said workpiece with a first dopant; and

implanting said workpiece with a second dopant in a second region that is a fraction of said surface, said second region having a center and a periphery, wherein said second region has a larger dose at said center than at said periphery.

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

11. The method of claim 9, wherein one of said first dopant and said second dopant is a p-type dopant and the other is an n-type dopant.

12. The method of claim 9, further comprising implanting said surface of said workpiece with said first dopant in a first region that is a fraction of said surface, said first region having a center and a periphery, wherein said first region has a larger dose at said center than at said periphery, and wherein said periphery of said first region and said periphery of said second region at least partially overlap.

13. The method of claim 12, wherein said first region and said second region extend to a depth deeper than a region formed by said implanting said entire surface of said workpiece with said first dopant,

14. A solar cell comprising:

a workpiece having a first surface;

a plurality of n-type regions in said first surface, each of said n-type regions having a center and a periphery, said center of said n-type region having a dose larger than in said periphery of said n-type region; and

a plurality of p-type regions in said first surface complementary to said plurality of said n-type regions, each of said p-type regions having a center and a periphery, said center of said p-type region having a dose larger than in said periphery of said p-type region,

wherein said periphery of said p-type region and said periphery of said n-type region at least partially overlap.

15. The solar cell of claim 14, further comprising a junction at a location where said dose in said periphery of said n-type region and said dose in said periphery of said p-type region are equal.

16. A solar cell comprising:

a workpiece having a first surface, said first surface being doped to a first conductivity and to a first depth;

a plurality of second regions in said first surface, each of said second regions being doped to a second conductivity opposite said first conductivity, each of said second regions having a center and a periphery, said center of said second region having a dose larger than in said periphery of said second region; and

a space charge region between said plurality of said second regions.

17. The solar cell of claim 16, wherein an entirety of said first surface is doped evenly to said first conductivity and to said first depth.

18. The solar cell of claim 16, wherein said first conductivity and said second conductivity are selected from the group consisting of n-type and-p-type.

19. The solar cell of claim 16, wherein a dopant profile of said periphery is configured to prevent shunting across said space charge region.

20. The solar cell of claim 16, further comprising a plurality of first regions in said first surface, each of said first regions being doped to