Measurement and analysis of bake dependencies of resist profiles are used to establish the critical role of diffusion and acid loss in lithographic performance. Imaging experiments carried out with APEX-E with postexposure bake temperatures above and below its glass transition temperature evidence widely dissimilar feature size dependencies attributable to different acid diffusion mechanisms in the glassy and the rubbery polymer, respectively. Examination of the mechanisms determining e-beam exposed resist image stability show that, when an acid loss mechanism is present, the initial amount of acid generated the reaction rate, and the diffusion mechanisms are essential hi predicting feature size dependence on postexposure bake conditions.