Tool ranking using aberration measurements in a high-volume manufacturing facility

The exposure tool is a critical enabler to continue improving the packing density and transistor speed in the semiconductor industry. In addition to increasing resolution (packing density) a scanner is also expected to provide tight control of the Across Chip Linewidth Variation, ACLV, (transistor speed). An important component of ACLV is lens aberrations. Techniques that measure in-situ the lens aberrations are now available. In a previous paper we reported good agreement between the first 25 Zernike coefficients measured in-situ using one of these techniques ARTEMIS and PMI (Phase Metrology Interferometry) data collected at the lens manufacturer. However questions have arisen as to the practicality of ARTEMIS, especially in view of its heavy reliance on a very large number of SEM images. We have measured the first 25 Zernike coefficients for 13 ASML 500/700 DUV Step & Scan systems in a high-volume wafer fab. In this paper we report on certain enhancements that were made to the best practice of ARTEMIS. We will also present a summary of the measurements taken and our first attempt to cluster the tools according to the aberrations measured.