Experimental measurement of photoresist modulation curves

Abstract

An approach to measurement of resist CD response to image modulation and dose is presented. An empirical model with just three terms is used to describe this response, allowing for direct calculation of photoresist modulation curves. A thresholded latent image response model has been tested to describe CD response for both 90 nm and 45 nm geometry. An assumption of a linear optical image to photoresist latent image correlation is shown as adequate for the 90 nm case, while the 45 nm case demonstrates significant non-linear behavior. This failure indicates the inadequacy of a "resist blur" as a complete descriptive function and uncovers the need for an additional spread function in OPE-style resist models.

True process variation aware optical proximity correction with variational lithography modeling and model calibration

“…Having this assumption, the line width (or CD) can be expressed as polynomials of exposure dose and focus error. Based on this idea, various polynomial fitting functions have been proposed [43,59,60]. In VLIM, we have diffusion length parameter d. We assume CD can also be expressed as a polynomial of d. By taking the z ↔ −z symmetry, we have only even order terms of z.…”