<title>Chemically amplified resist process for 0.25-um-generation photomasks</title>

A chemically amplified negative electron beam resist process is developed for fabricating 0.25 micrometers devices 4X magnification reticles. In order to improve a critical dimension (CD) uniformity on reticles, a precise temperature controllability in post exposure baking is realized. Dry etching for Cr is also adopted for getting an appropriate pattern fidelity down to submicron on reticles to meet requirements for such an optical proximity effect correction. Under the optimized process conditions, a CD uniformity of 16 nm in 3 (sigma) is achieved on reticles. A CD linearity of down to 0.8 micrometers on the reticles is ensured as well. Actual 0.25 micrometers device reticle production results show that the CD mean variation is controlled within +/- 43 nm. It is confirmed that an advanced 4X reticle fabrication process for 0.25 micrometers device generation is realized.