Fabricating 0.10-μm line patterns using attenuated phase shift masks

We studied the optical proximity effect, the depth of focus (DOF) and the mask-error-enhancement factor of ArF attenuated phase shift masks (att. PSMs) for application to 0.1-mum logic gate patterns. We made an ArF att. PSM with 6% transmittance and exposed it with an ArF scanner, NA = 0.60, using a 0.4-mum-thick chemically amplified positive resist. We evaluated the performance under these conditions, We obtained the best result with annular illumination. The critical dimension variation range for the target was 23 nm from semi-dense to isolated line patterns. That was large but we could suppress it with bias optical proximity correction. The common DOF for both semi-dense and isolated line patterns was 0.3-mum, which is large enough to print 0.1-mum logic gate patterns. We confirmed good performance for fabricating 0.1-mum-logic gates with the ArF att. PSM and annular illumination.