New modified silica glass for 157-nm lithography

Projection photolithography at 157 nm is now under research as a possible extension of current 248 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 2 nm. We also have developed hard pellicle with 300 micrometers thickness. Its transmission is over 92 percent when AR films are coated on both surfaces. This hard pellicle also has a very good durability to F2 laser.