Accurate determination of 3D PSF and resist effects in grayscale laser lithography

Abstract

Accurate calibration of the optical and resist parameters is invaluable for the computation of the dose distribution needed to fabricate a desired non-binary photoresist topography. This paper presents a method for precisely evaluating the 3D point spread function (PSF) and model parameters for the resist processes in laser grayscale lithography. The 3D PSF and resist model parameters were determined by fitting a detailed model of the grayscale process to experimental measurements of an array of test patterns. Measuring the entire 3D profile provides more data for process calibration, and therefore a more accurate model. The derived model parameters were applied to correctly predict the topography of sawtooth patterns.