The dissolution of polymer thin films plays an important role in microelectronics fabrication. One example can be found in the processing of photoresists, thin polymer films that are used to produce the circuit patterns for semiconductor devices. In the last step in the lithographic process the exposed and processed polymer film is immersed in a liquid developer to selectively dissolve either the exposed or the unexposed regions to give, respectively, a positive or negative tone replica of the mask.

A classical model for polymer dissolution is depicted below. Upon immersion of the polymer film into the liquid, the solvent permeates the film to form a swollen gel layer. Increased mobility in the swollen layer promotes polymer chain disentanglement and dissolution. This model describes physical dissolution of a polymer, for example by an organic solvent.

Most modern chemically amplified (CA) photoresists are based on reactive dissolution where the liquid developer, an aqueous solution of hydroxide ion, ionizes acidic pendant groups producing water-soluble polyionic polymer chains. The central role of this acid-base reaction leads to a more complex dissolution process. The imaging chemistry modulates the number of ionizable groups and therebv the rate of dissolution. The polymer structures that typify those found in CA resists are shown below.

The functional properties of a photoresist derive in part from its dissolution properties. For example, a nonlinear change in dissolution rate with extent of deprotection in a CA resist can act to sharpen the acuity of the final relief image compared to its latent image prior to development.