The work presents a unique investigation of the role of postexposure bake (PEB) on resist insolubility, FEB reaction kinetics, and the high resolution behavior of Microposit(TM) SAL-601. Patterns of 20-100 mu m rectangles and single pass isolated lines were written on a JEOL JBX-5DII e-beam lithography system operated at 50 kV. The effects of FEB temperatures of 90-110 degrees C for periods of 1-11 min on resist insolubility and linewidth were examined. The samples were developed in MF-322 or acetone. The range of patterns allowed measurement of both the resist exposure curves and the line spread for each FEB condition. Insolubility in MF-322 can result from protection reactions and/or crosslinking reactions. Acetone insolubility, a characteristic of crosslinked resist, was observed at FEB temperatures of 100 degrees C and above. At 90 degrees C,: acetone insolubility (crosslinking) was observed only after a FEB of 11 min. From the resist exposure curves for a sequence of FEB times, reaction orders for the FEB processes that led to resist insolubility were determined. At temperatures of 100-110 degrees C, reaction orders of 2.4 and 2.1 were obtained for reactions that led to insolubility in MF-322 and acetone, respectively. At 90 degrees C the order of reaction leading to MF-322 insolubility was 1.8. PEBs at 90 degrees C for 3 and 6 min produced the finest lines, with linewidths less than or equal to 50 nm over an order of magnitude range in dose. An acid diffusion mth order reaction model, which allows for H+ loss to the surface, was introduced to analyze the linewidth measurements. In the 105-110 degrees C temperature range, the model best fit the data with diffusion coefficients-of 4-8 nm(2)/s and acid loss rates of 0.003-0.005%/s.