Writing-strategy for a high-throughput SCALPEL system

Successful deployment of SCALPEL for several post-optical production lithography generations requires a unique optimum writing-strategy, Since the electron optics sub-field and the strutted mask pattern segment are both smaller than the final device image area, SCALPEL utilizes a stitching approach to image-formation. A dynamic sub-field placement scheme, or "writing-strategy" must; provide precise two-dimensional stitching at high speed, and eliminate mask strut images on the wafer. It should also provide the extended dynamic lens field necessary for good throughput, while minimizing all non-exposure times per wafer and maintaining the time-averaged current near the instantaneous space-charge limit. The preferred writing-strategy replaces mechanical stage acceleration events with beam deflection wherever possible. The unique writing-strategy presented here also generates the required two-dimensional seam-blending dose-profiles, which are vital to robust CD control with stitching.