A Generalized Dill Exposure Model for Negative Thick Photoresist

In this paper, Dill's classical exposure model for positive photoresist is generalized to fit negative photoresist. Based on Dill's model, the differences between positive and negative photoresist is analyzed and then the equations of chemical kinetics inside the SU-8 negative photoresist are established. To consider the scattering and refraction of light in thick photoresist, angular spectrum theory is used to calculate the diffractive field inside thick photoresist. A new exposure model is established for negative thick photoresist.