Real Time Monitoring of Exposure Controlled Projection Lithography with Time-Varying Scanning Points

Exposure Controlled Projection Lithography (ECPL) is a stereolithographic process in which photopolymer resin is used to fabricate lens shaped features. During this process, a dynamic mask projects radiation patterns through a transparent substrate onto the photopolymer resin to grow features from the substrate surface. We present a novel method to monitor the photopolymerization process in real-time with higher spatial resolution in a plane perpendicular to the polymerization growth. A Spatial Light Modulator (SLM) was incorporated into our Interferometric Cure Monitoring (ICM) system, which periodically moves the positions of the scanning points onto the curing area to estimate the cured part height. This time-varying scanning strategy avoids interference caused by points too close to one another and enables higher spatial resolution than fixed scan patterns. This time-varying multi-point monitoring approach is experimentally validated to measure the cured part height and the lateral dimensions of the cured part at the substrate level.