Low molecular weight negative tone chemically amplified resist has been exposed with 100 kV electron beam writer with a postexposure bake temperature varying between 85 and 100 degrees C. Isolated lines, with feature size ranging from 20 up to 100 nm, have been characterized with scanning electron microscopy and critical dimension atomic force microscopy. A simple kinetic reaction law and lateral acid diffusion into the resist layer were taken into account for the cross-linking reaction simulation. Top view and full three-dimensional measurements of resist feature have been fitted with an analytical expression. A cost function was introduced to extract the reaction order (m) and the acid diffusion coefficient (D) of the second Fick's law. Whatever the process temperature used, a constant value for m (m = 2.6) was found, and D was found to vary from 2 to 45 nm(2)/S for a postexposure bake temperature of 85 and 100 degrees C, respectively. Depending on the metrology technology used for resist characterization resist parameter extraction may be significantly impacted, especially for very narrow resist line simulation. (c) 2005 American Vacuum Society.