The dimension of patterns written with the scanning probe in resist is determined by the exposure dose and can be accurately controlled down to about 25 nm linewidths in 50-100 nm thick resist. Since we use thin resists for scanning probe lithography, we must take some care to transfer the resist patterns into the underlying film or substrate. We have achieved sucessful pattern transfer of features down to 25 nm in width using direct plasma etching and lift-off techniques.
Cross-sectional SEM images of etched silicon features patterned by scanning probe lithography. (a) 50-nm-wide line written in SAL601 and etched 300 nm into the silicon using an HBr+O2 high density plasma (6:1 aspect ratio). (b) 26-nm-wide line written in PMMA and transferred through lift-off and anisotropic etching (NF3) into the silicon substrate. The etch depth is 260 nm, giving the line an aspect ratio of 10:1.
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image formation
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