Chemically amplified resist process for 0.25-μm generation photomasks

A chemically amplified (CA) negative electron beam resist process is developed for fabricating 0.25 μm devices 4X magnification reticles. In order to improve a critical dimension (CD) uniformity on reticles, a precise temperature controllability in post exposure baking (PEB) 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 as optical proximity effect correction. Under the optimized process conditions, a CD uniformity of 0.016 μm in 3σ is achieved on reticles. A CD linearity of down to 0.8 μm on the reticles is ensured as well. Actual 0.25 μm device reticle production results show that the CD mean variation is controlled within ± 0.040 μm. It is confirmed that an advanced 4X reticle fabrication process for 0.25 μm device generation is realized.