CD uniformity control via real-time control of photoresist properties

Abstract

Critical dimension (CD) or linewidth is one the most critical variable in the lithography process with the most direct impact on the device speed and performance of integrated circuits. Photoresist thickness is one of the photoresist properties that can have an impact on the CD uniformity. Due to thin film interference, CD varies with photoresist thickness. In this paper, we present an innovative approach to control photoresist thickness in real-time during thermal processing steps in the lithography sequence to control CD. As opposed to run-to-run control where information from the previous wafer or batch is used for control of the current wafer or batch, the approach here is real-time and make use of the current wafer information for control of the current wafer CD. The experiments demonstrated that such an approach can reduce CD non-uniformity from wafer-to-wafer and within-wafer.