The impact of diffraction effect on the dimensional precision of UV-lithography based on SU-8 photoresist was investigated. An improved UV exposure model based on Fresnel diffraction theory was proposed to use in predicting the dimensions of photoresist microchannels and their variations with changes in the lithographic parameters. In four different experiments

the characteristic width of photo masks were 50 μm

100 μm

200 μm and 400 μm

respectively

and the exposure dose on the surface of SU-8 photoresist was 400 mJ/cm

2

. In the experiments

the silicon was chosen as substrate. The top width

bottom width and thickness of SU-8 photoresist of cross section of microchannel in four different experiments were measured with SEM. The distribution of exposure dose in the SU-8 photoresist was simulated numerically with MATLAB. Comparing the simulative results with experimental results

a good agreement between them is acquired. The simulation results can be used to instruct the further experiments.