Critical dimension control at stitched subfield boundaries in a high-throughput SCALPEL® system

Scattering with angular limitation projection electron-beam Lithography (SCALPEL(R)) is a stitching Lithography system, using a segmented mask pattern which is assembled on the wafer by dynamic imaging. Critical objects may lie on the original pattern segment boundaries (seams), but their stitched images must adhere to conservatively interpreted +/-10% critical dimension (CD) control requirements. Stitching with butted (touching) spatial image parts requires an aggressive placement-error allocation of approximately +/-CD/20, along with allowed values for dose control, mask, resist, and process in the CD control budget. Further analysis has shown that a seam-blending scheme increases the stitching-error tolerance by as much as five times, and allows redistribution of all values in the CD error budget. The seam-blending approach provides overlapped image portions in a small area common to neighboring segments which receive complementary illumination dose portions. (C) 1998 American Vacuum Society. [S0734-211X(98)15706-2].