Built-in lens mask lithography (challenge for high-definition lens-less lithography)

Abstract

A novel technique of photolithography using a proximity exposure system—named built-in lens mask lithography—is proposed. The built-in lens mask having complex optical transmittance emulates the optical propagation plane in the focusing of an image having an arbitrary pattern. The complex transmittance of the built-in lens mask is computationally obtained for an arbitrarily designed pattern and the transmittance and phase shift are binarized, which is easily achieved using conventional phase mask technology. The performance of built-in lens mask lithography is numerically studied and experimentally confirmed using a conventional proximity exposure system. The results of the numerical study and experiments agree and confirm the enhancement of the critical resolved feature size to 3.0 μm at a focal length of 55 μm using the built-in lens mask.