The development of standard extreme ultraviolet (EUV) lithography photoresists with a CO2 compatible salt (CCS) and supercritical carbon dioxide (scCO(2)) solution hat; several advantages over typical trimethylammonium, hydroxide development, including reduced image collapse and line width roughness in the resulting microchip features. The mechanism and characteristics of the CCS/scCO(2) development process are currently being examined. In this paper, the sorption behavior of CO2 and the CCS onto a bare SiO2 surface and into the photoresist was studied using a quartz crystal microbalance (QCM). From the adsorption studies of CO2 and CCS/CO2 onto a bare SiO2 surface, it was found that the CCS begins to adsorb at 8.0 MPa at a temperature of 35 degrees C and at 9.4 MPa at a temperature of 50 degrees C. The adsorption of the CCS was favored and driven by entropy changes. The absorption Of CO2 into the glassy photoresist resin was also measured with QCM and found comparable to CO2 absorption in glassy polystyrene for 35 and 50 degrees C up to a pressure where the photoresist is believed to dewet from the substrate. The diffusion behavior during CO2 absorption was found to be comparable to that of small fluorescent molecule diffusion in a CO2 swollen polystyrene.