Enhancement of KRS-XE for 50 keV Advanced Mask Making Applications

KRS-XE, a high performance chemically amplified photoresist designed specifically for e-beam mask making applications, has been enhanced to achieve reduced “footing” on chrome oxide surfaces while still maintaining the original lithographic characteristics that make KRS-XE a promising mask making candidate. These attributes include high resolution, superior bake latitudes, high vacuum stability, coated shelf life of greater than 2 months, and, most notably, the absence of a post exposure bake. In conjunction with the footing reduction the requisite sensitivity requirement of <10uC/cm2 with 50 keV exposure tools has been achieved while retaining the robust process latitude previously reported for this resist. Through a careful study of the photoresist formulation components a route to the ultra-high sensitivity of <2.5uC/cm2 at 50 keV has been elucidated which will further enhance throughput, decrease heating effects, and potentially be a suitable resist for e-beam projection lithography (EPL).