Dependence of photoetching rates of polymers at 193 nm on optical absorption depth

Mixtures of poly(methyl methacrylate) and poly(α-methyl styrene) were prepared and their optical absorption coefficients at 193 nm were measured. A study of photoetching rate of these polymeric materials using an ArF excimer laser at 193 nm shows two regions of distinctly different etching characteristics. At relatively high fluences (>300 mJ/cm2) the photoetch rate decreased with increasing absorption in the polymer films, while at lower fluences, an optimum range of absorption coefficients was found to give the maximum photoetching rate.