Fabrication of Continuously Varying Thickness Micro-Cantilever Using Bulk Lithography Process

This paper presents fabrication of varying thickness polymer micro-cantilever using recently developed and characterized, single scan, three-dimensional (3D) micro-fabrication process termed as “bulk lithography”. The process allows fabrication of 3D microstructures that demonstrate continuous variation in the thickness direction as against the discrete variation provided by the normal microstereolithography (layer-by-layer) and other VLSI processes. The required depth variation is obtained during fabrication by allowing unconstrained depth photopolymerization and varying laser exposure while scanning. Towards goal to achieve the control over cured depth and smooth free surface (down facing surface), the process is characterized for cured depth and width under wide range of energy dose at different exposure duration. The depth characterization, represented earlier in a form of an empirical model, is used programmatically to impose any desired spatial intensity variation during scan. Additional width characterization, presented in this paper, is used to optimize the line spacing for achieving smooth unconstrained surface. Specific case of fabrication of tapered micro-cantilever is demonstrated with the proposed technique.