Process optimization and proximity effect correction for gray scale e-beam lithography

Three-dimensional microstructures find applications in diffractive optical elements, photonic elements, etc., and can be efficiently fabricated by e-beam lithography. Good process control and efficient proximity effect correction are important for achieving the desired structures. With polymethylmethacrylate as the resist, a process optimization of different develop conditions is carried out to identify a process that is most conductive to gray scale features. A novel proximity effect correction scheme called effective dose-depth (EDD) method is proposed. Using the EDD method for grating design and the optimized process, blazed gratings have been fabricated with excellent uniformity and low surface roughness. (c) 2006 American Vacuum Society.