IMPLANTING A SOLAR CELL SUBSTRATE USING A MASK

• US 20100062589A1
• Filed: 09/08/2009
• Published: 03/11/2010
• Est. Priority Date: 09/10/2008
• Status: Active Grant

• Current Assignee: Varian Semiconductor Equipment Associates Incorporated (Applied Materials Incorporated)
• Original Assignee: Varian Semiconductor Equipment Associates Incorporated (Applied Materials Incorporated)
• Inventors: Weaver, William, Anella, Steven
• Granted Patent: US 8,202,789 B2
• Time in Patent Office: Days
• US Class Current: 438/527
• CPC Class Codes: G03F 1/20 Masks or mask blanks for imaging by charged particle beam [CPB] radiation, e.g. by electron beam; Preparation thereof
• CPC Class Codes: H01J 2237/31711 using mask
• CPC Class Codes: H01J 37/3171 for ion implantation
• 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 31/028 including, apart from doping material or other impurities, only elements of Group IV of the Periodic Table
• 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: Y02E 10/547 Monocrystalline silicon PV cells

Abstract

Various masks for use with ion implantation equipment are disclosed. In one embodiment, the masks are formed by assembling a collection of segments and spacers to create a mask having the desired configuration. This collection of parts is held together with a carrier of frame. In another embodiment, a panel is formed by machining open-ended slots into a substrate, so as to form a comb-shaped device. Two such panels may be connected together to form a mask. In other embodiments, the panels may be used sequentially in an ion implantation process to create interdigitated back contacts. In another embodiment, multiple masks are overlaid so as to create implant patterns that cannot be created effectively using a single mask.

Claims

1. A mask, suitable for use in a ion implantation system, comprising:

a plurality of segments, each having a common length, and a width;

a plurality of spacers, each of said spacers have a length less than that of said segments and wherein said spacers are placed between said segments to create openings between said segments through which ions may pass; and

a frame, adapted to hold said plurality of spacers and said plurality of segments in place, wherein one dimension of said mask is defined by said common length and a second dimension of said mask is defined by the sum of the widths of said stacked segments and said spacers.

2. The mask of claim 1, wherein each of said plurality of segments has the same width.

3. The mask of claim 1, wherein said plurality of segments has a plurality of widths.

4. The mask of claim 1, wherein each of said plurality of spacers has the same width.

5. The mask of claim 1, wherein said plurality of spacers has a plurality of widths.

6. The mask of claim 1, wherein said frame comprises a clamp.

7. The mask of claim 1, wherein each of said segments has two opposite ends, and wherein one of said spacers is placed between the first end of a first segment and the first end of a second segment, and a second of said spacers is placed between the second end of said first segment and said second end of said second segment, and wherein said opening is defined as the space between said first and second segments and between said first and second spacers.

8. The mask of claim 7, further comprising a third spacer located between said first and second spacer, thereby dividing said opening into two smaller openings.

9. A mask, suitable for use in an ion implantation system, comprising:

a first panel and a second panel, wherein each of said panels comprises a member and a plurality of strips extending from said member, wherein said plurality of strips defines a plurality of slots between said plurality of strips through which ions may pass; and

a frame adapted to hold said two panels.

10. The mask of claim 9, wherein said panels each form a comb shaped structure and each of said strips comprises a distal end furthest from said member, and wherein said frame is adapted to hold said first panel and said second panel such that the distal end of a strip from said first panel abuts a distal end of a corresponding strip from said second panel.

11. The mask of claim 9, wherein said panels each form a comb shaped structure and said frame is adapted to hold said panels such that a strip from said first panel overlaps a corresponding strip from said second panel.

12. The mask of claim 9, wherein each of said panels comprises a second member opposite said first member, such that said strips form cross members between said members, and wherein said frame is adapted to overlay said first panel and said second panel in orthogonal orientations, so as to create a checkerboard pattern.

13. The mask of claim 9, wherein each of said panels comprises a second member opposite said first member, such that said strips form cross members between said members, and wherein said frame is adapted to overlay said first panel and said second panel in the same orientation, and to move said first panel relative to said second panel so as to reduce a size of an effective opening, wherein said effective opening is defined as the region where ions may pass through both panels.

14. A method of creating an interdigitated implant region in a substrate, comprising:

using a first mask, wherein said first mask comprises a first member and a first plurality of strips extending from said first member so as to form a first comb shaped structure, wherein the spaces between said first plurality of strips define a first plurality of open-ended slots through which ions may pass;

placing said first mask between an ion source and said substrate;

implanting ions into said substrate, where said ions are not implanted in the region covered by said first mask, thereby creating a first comb shaped implant region having a first implanted area and a first plurality of implanted strips extending therefrom, said first plurality of implanted strips corresponding to said first plurality of open-ended slots in said first mask;

using a second mask, wherein said second mask comprises a second member and a second plurality of strips extending from said second member so as to form a second comb shaped structure, wherein the spaces between said second plurality of strips define a second plurality of open-ended slots through which ions may pass;

placing said second mask between an ion source and said substrate, such that said second mask is oriented such that said second plurality of strips of said second mask cover said first plurality of implanted strips in said first comb shaped implant region, said second plurality of open-ended slots in said second mask positioned above said first plurality of open-ended slots in said first comb shaped implant region, and said first implanted area of said first comb shaped implant is covered by said second member of said second mask; and

implanting ions into said substrate, where said ions are not implanted in the region covered by said second mask, thereby creating a second comb shaped implant region, having a second implanted area and a second plurality of implanted strips extending therefrom.