Chrome and resist thickness are limiting factors for final resolution on mask. The trend in mask manufacturing is consequently moving towards thinner chrome and resist films. The Sigma7300 is a 248nm DUV laser pattern generator with optical resolution approaching 100nm. The earlier standard mask blank for the mask writer had 1030Angstrom thick AR8 chrome together with 4000Angstrom FEP-171 resist. To fully benefit from the resolution capability of the mask writer, this study aimed to investigate the 730Angstrom thick NTAR7 chrome together with thinner FEP-171 resist. The dry etch characteristics of thin chrome and thin resist were also studied. As a first step, a set of plates with varying resist thickness was exposed to extract the swing curve. The resist thickness ranged from 3050Angstrom - 3600Angstrom in steps of 50Angstrom. The fitted curve based on the dose required to break through the resist (dose-to-clear) for different thicknesses showed a maximum at approximately 3200Angstrom. A resolution improvement of about 10nm was achieved in this resist thickness compared to the earlier 4000Angstrom film. Design of Experiments (DoE) was used to perform a screening of the dry etch process on NTAR7 and the 3200Angstrom resist. All plates were exposed using the Sigma7300. Etching was performed on a UNAXIS Gen III Mask Etcher with standard CI2/O-2/He gas mixture. The dry etch process developed from the DoE responses was used to characterize the lithographic performance on mask from the Sigma,7300 together with the new optimized blanks. CD linearity <10nm (range) was demonstrated both for clear and dark isolated lines down to 180nm line width. Global CD uniformity <6nm (3sigma) was achieved and very well defined chrome profiles for 150nm isolated clear lines and 130 nm isolated dark lines were demonstrated.
