AG2TE/AS2S3, A TOP-SURFACE, HIGH-CONTRAST NEGATIVE-TONE RESIST FOR DEEP-ULTRAVIOLET SUBMICRON LITHOGRAPHY

The sensitivity of the Ag2Te/As2S3 system has been measured as a top-surface imaging, negative-tone resist between 632.8 and 193 nm. The sensitivity at g-line (435.8 nm) and i-line (365 nm) is of the order of 5 and 0.5 J/cm2, respectively, and is much too low to take advantage of the significant advantages of this resist. These advantages are high contrast (approximately 10), an edge effect which compensates for the reduction of optical intensity at line edges and latent image formation in a layer whose thickness is significantly less than the depth-of-focus of high resolution stepper optical systems. Measurements at 248 and 193 nm show significantly higher sensitivity of 350 and 80 mJ/cm2, respectively, suggesting that this system may possess practical potential at these wave lengths. Exposures on a GCA XLS-7500 stepper with 0.42 NA at 365 nm have yielded 0.35 mum linewidths.