Simulation Of MEMS Projection Lithography Based On FDTD

In MEMS manufacturing field,lithography is one of the most important.As the size of devices gradually decreases,the complexity of lithography process increases greatly,and it undoubtedly requires a lot of time and expense to carry out various experiments in the laboratory or on the production line,which makes the lithography process simulation become an increasingly useful method.Using lithography simulation can not only accurately predict the process results under different parameters,but also help scientists and engineers to understand the intrinsic principles of lithography and discover new technologies.In the specific process,exposure can be divided into three ways,contact lithography,proximity lithography and projection lithography.Our research group has studied contact lithography and proximity lithography,but the simulation model of projection lithography is still unknown.At the same time,most of the IC lithography simulation research only focuses on the image simulation,which is not suitable for the simulation of high aspect ratio structure in MEMS.Therefore,this article focuses the projection lithography of thick photoresist,fully considering the effect of light diffraction,mask template graphics,optical material features,light vector characteristics.The derivation is strictly based on Maxwell's electromagnetic field theory and vector imaging.In this paper,a novel two-dimension and three-dimension projection lithography intensity distribution model is first proposed.Combined with the following modules,a computer simulation software which can accurately simulate the whole lithography process is obtained.The theoretical derivation and algorithm flow are given,and the processing methods of excitation source,amplitude and phase extraction,algorithm boundary conditions and the connection between the projection objective lens and other regions are described in detail.Taking SU-8 adhesive as an example,the light intensity contour distribution map and the developed morphology were given.The influence of vertical incidence,oblique incidence,exposure Angle,focal plane position and other factors on the light intensity distribution in the photoresist were considered.According to the graph,the simulation results and experimental results are compared and analyzed to verify the correctness of the proposed algorithm,which has a certain inspiration for future research and software commercialization.