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 patten 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 2D 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 2D seam-blending dose-profiles, which are vital to robust CD control with stitching.