Laser lithography – exposure of structure and modelling of Gaussian beam.

Abstract

Various types of micro-structures can be prepared using direct writing laser lithography. The majority of these structures are optical diffractive components, which are in high demand. However, implementation of the desired structure size and shape may be problematic due to the different non-linear responses of different types of photoresists to the exposure dose. Optimization of lithographic parameters and an understanding of photoresist chemistry is needed to solve these issues. To characterise the exposure process, the lithographic laser beam is approximated by the mathematical model of the Gaussian beam. Subsequently, the model is used to make a simulation of the real lithographic exposure with photoresist optical constants. By comparing the simulation with the measured data, the optical properties of the photoresist (such as beam divergence and absorption) can be described, and optimization of required parameters can be performed.