Research On Optical Lithography Of Thick Film Resists

Optical lithography of thick film resists is an important approach with easy for fabrication, low cost and compatible with integrated circuit(IC) process, while used for fabrication of microstructure with large depth in the field of micro-optics as well as micro-fluidic and micro-electromechanical system(MEMS). With the requirement of increasing applications in recent years, modeling and processing of thick film resists become an important field. When compared with thin film lithography, however, thick film lithography is a much more complicated process, which involves quite a few nonlinear factors. Motivated by fabrication of high-fidelity microstructure, the thick film lithography is studied not only theoretically but also experimentally in this dissertation.Firstly, we have developed a scalar model for lithography of thick film photoresist by using the angular spectrum theory, in which the thick film photoresist is divided into many homogeneous layers, and the diffractive optical imaging distribution in photoresist is regarded as superposition of different spectrum plane waves. The fast Fourier transform (FFT) has been converted into a convolution calculation to keep the computation accurate and reduce computation cost. Moreover, a vector model is established in which Fourier modal method, mostly applied to study the diffractive properties of grating, is adopted to analyze the diffractive image field in thick film resists. Both of the models have advantages with low computation cost and high computation precision.Secondly, The software package for optical lithography simulation of the whole process is programmed, in which diffractive field, distribution of PAC and surface profile after development can be simulated. It is very useful to not only understand the mechanism of lithography process, but also provide a way for process optimization. In addition, the effects of illumination wavelength, gap distance and absorption coefficient on the profile quality after development are simulated and...