The response of unentangled polymer thin films to aqueous hydroxide solutions is measured as a function of increasing weakly-acidic methacrylic acid comonomer content produced by an in-situ reaction-diffusion process. Quartz crystal microbalance with energy dissipation and Fourier transform infrared spectroscopy measurements are used to identify four regimes: (I) non-swelling, (II) quasi-equilibrium swelling, (III) swelling coupled with partial film dissolution and (IV) film dissolution result from chemical heterogeneity in local composition of the polymer film. The conversion of a hydrophobic protection group to a weakly-acidic one increases the size of hydrophilic parts of the film that lead to film swelling, while decreasing the structure of the hydrophobic matrix that can provide physical cross links and maintain film stability. These observations challenge models of photoresist film dissolution in which onset to swelling and partial film dissolution could shed light on image quality.
Pub Type: Journals
dissolution, line edge roughness, photoresist, reflectivity, swelling