Process Optimization of Single-Step Photolithography

Due to the precision and sizing requirements of popular semiconductor devices nowadays, thickness control and uniformity optimization of the photoresist during the photolithography process are thought to be critical issues for process engineers to consider. In this paper, the parameters affecting photoresist thickness are thoroughly analyzed and an economic and novel approach improving uniformity during spin coating is presented. In the Integrated Nanosystems Research Facility at the California Institute for Telecommunications and Information Technology (Calit2), 8 silicon wafers were coated with a positive photoresist named Shipley 1827 for this purpose. At the end of this paper, the author concludes several essential but easily ignored factors that can affect the uniformity and thickness of the photoresist. By following the given rules, high quality single-layer silicon wafer can be coated at ease.