Implanting a solar cell substrate using a mask

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.