Absorption coefficient and sensitivity of positive and negative resists in the vacuum ultraviolet region

Absorption coefficients for the resist materials (polymethyl methacrylate (PMMA) and partially chloromethylated polystyrene (CMS-DU)) were obtained in the vacuum ultraviolet (VUV) region. Negative and positive resist characteristics were investigated using a coherent VUV radiation source (λ=110-150 nm) generated by two-photon resonant four-wave mixing in Cd vapor. A very low exposure energy of approximately 1 mJ/cm 2 was realized by employing a very thin resist film and using VUV light from the high-absorption region of the resist materials.