<title>Process latitude for 100-nm dimensions for e-beam lithography in SAL-601</title>

Abstract

This paper focuses on the process latitude for achieving 100-500 nm dimensions in SAL-601 e-beam resist. Si wafers were coated with 140 nm of resist and lithographically exposed with a JEOL JBX-5DII e-beam lithography system, operated at 50 kV and a probe standard deviation, (sigma) , of approximately 10 nm. Post exposure bake (PEB) conditions were 105 degrees C for 1, 3, and 10 min. and 110 degrees C for 1 min. The measured backscatter coefficient was 0.51, in agreement with out Monte Carlo simulation results. Resist thickness measurements showed a factor of 2 variation in sensitivity with PEB conditions but no change in contrast. The measured linespread functions for isolated lines could be fit to single Gaussians with (sigma) of 27-33 nm, depending of the PEB conditions. The measured widths of the linespread functions were more than a factor of 2 larger than predicted by the Monte Carlo simulation. The PEB condition of 105 degrees C for 1 min. showed slightly better dose latitude than the other PEB conditions for fabricating gaps between pads. Still the process latitude became acutely narrow in patterning 100 nm gaps. For 20 micrometers pads the dose latitude was less than 3 percent. There was no single dose that could produce a gap of less than 250 nm in a tower pattern with pad widths of 0.5 to 20 micrometers . The results are compared to calculated dose profiles that incorporate both measured linespread functions and those generated by a Monte Carlo code.