Simulation Of Contact UV Lithography Process For SU-8 Photoresists

Lithography plays an important role in microfabrication. It is one of the bottleneck in manufacturing semiconductor components. Manufacturers of semiconductor chips need to predict future lithographic capabilities as accurately as possible, as this information influences all the other process changes (ion implantation, oxidation, diffusion, etching, deposition, etc.) that will jointly need to be made.Process technology advances with major overhaul or complete replacement of process equipments. Semiconductor manufacturers require careful planning and checks to ensure that the investment will enable the desired goal to be reached. Simulation is one of the key tools used for making these checks.With rapid growing of information technology, microfabrication and integration are the two main trends of devices. Because high aspect ratio structure can be produced with UV lithography using SU-8 photoresist, it is very fittable for manufacturing high aspect ratio microstructures. SU-8 photoresist is widely used, especially in the area of UV expose like UV-LIGA. The process parameters for SU-8 are currently mainly optimized by repeatedly experiments. The SU-8 profiles after UV lithography is simulated in the work in this paper.This paper reports a set of simulation models of contact UV lithography for SU-8 photoresist and its C/C++ program. The models are based on usual simulation models for chemically amplified photoresist added with swell model and the model for depth- dependent dissolution rate effect. The new set of models are more proper for lithography simulation for thick SU-8 resist. The comparision of simulation results and experiement results shows total error between them is less than 6%.The 2-D simulation of thick SU-8 photoresist profile after UV lithography is presented. The SU-8 photoresist is a chemically amplified, epoxy based negative resist. The simulation in the work is based on the earlier research of chemically amplified photoresist and lithography mechanism and characters of SU-8 resist. The earlier research has been focused on modeling thin chemically amplified photoresist for submicron lithography and little has been made on modeling thick chemically amplified photoresist. Therefore, novel models for thick chemically amplified photoresist which fit well characters of SU-8 resist is set up.To begin with, the earlier work for lithography simulation is introducted, which includes aerial image model, expose model for DNQs and chemically amplified photoresists(CARs), postbake model for CARs, and generic development model. Followed is the description of how the SU-8 is evolved in the processes of exposing, postbaking and developing from physical and chemically reaction point of view. Because of specialty of the application of SU-8 photoresists, two novel models are set up for thick SU-8: swell model and depth-dependent dissolution rate model.The last chapter involves the flow chart of the simulation with detailed explaination of the program in C/C++. At the end of the paper text, the comparion of simulation results and experiment results are done in two ways: comparing graphs and comaparing numeric width values. The errors are calculated for each comparion with the largest error 6μm and the least 2μm for 100μm line-width. It can said that the total error is less than 6%. The appendix is the C/C++ code for the program.