A simulation model on photoresist SU-8 thickness after development under partial exposure with reflection effect

The negative photoresist SU-8 is often used to fabricate thick micro structures. It was known that reflection from the interface between SU-8 an the substrate surface would affect the thickness after development and profile of SU-8 structures. However, the model to predict the thickness after development of SU-8 under reflection effect has not been reported yet. Here, a simulation model to predict SU-8 thickness after development under partial exposure with reflection effects is proposed. Two kinds of SU-8 micro structures with different exposure dosages and coated thickness are fabricated on glass substrates to demonstrate the capability of the proposed model. For different exposure dosages or coated SU-8 thickness, the maximum difference between simulated and experimental results is shown to be less than 3.1%, which verifies the accuracy of the proposed model.