Projection photolithography at 157 nm is now under research as a possible extension of current 248 nm and planned 193 nm technologies. We have succeeded in the development of the modified fused silica glass 'AQF' for 157 nm lithography. In this paper, we present the performance of the newest material; AQF/Ver. 2.1. Transmission and its uniformity at 157 nm is better than 78 +/- 1.5 percent, and birefringence is within 2nm. The surface flatness is less than 0.5 micrometers , and surface defects over 0.4 micrometers in size are free.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.