Maskless microfabrication of semiconductor devices by non-linear photopolymerization

Abstract

We propose a method of optical lithography that uses photo-polymerization via non-linear photon absorption of a photoresist to define two-dimensional (2D) structures on a semiconductor substrate. The nonlinear photon absorption is achieved using a focused femtosecond-pulse near-infrared laser to write a predetermined pattern on the wafer without the use of a photo-mask. The patterns are stored in a computer and via electronic control of two galvanometer-mounted scanning mirrors the focused laser beam traces the 2D structures on a photoresist-coated substrate. Hence, direct writing of patterns with a focused laser beam defines the region of the photoresist for etching, rather than being confined by the pattern on an available photo-mask. Arbitrary patterns can be fabricated and offers high potential for optimum design of semiconductor devices. Moreover, non-linear absorption can be exploited to allow for feature sizes beyond the optical diffraction limit.