Proximity effect reduction in high voltage electron-beam lithography by bias exposure method

Abstract

The proximity effect reduction was achieved by electron beam (EB) uniform exposure (bias exposure) on the target covered with PMMA resist of 1 μm in addition to conventional high voltage EB writing. At an acceleration voltage of 50 kV and a dosage of 50 μC/cm2, a pattern size error of 0.5 μm pattern due to the proximity effect amounted to 0.25 μm, which was improved to 0.12 μm by bias exposure. When dosage was large, the pattern size error was further improved by bias exposure. For 50 kV and 140 μC/cm2 writing, 0.25 μm pattern including isolated window, line and window, and isolated line was formed with an accuracy of ±0.025 μm. The pattern size error for conventional EB writing was almost independent of dosage. For 20 kV and 20 μC/cm2 writing, the pattern size error was hardly improved by bias exposure.