The process of record for mask fabrication on CORE pattern generators has been OCG-895i positive resist. This process has demonstrated excellent performance in a production environment, however it is recognized that having both negative and positive resist process capability would significantly improve the flexibility of most mask fabricators. The CORE exposure wavelength of 363.8 nm is close enough to i-line (365 nm) to provide the opportunity to use many of the i-line resists developed for wafer lithography. Negative acting resists sensitive at i-line are now becoming available. The most popular chemistry for this application has been acid catalyzed chemical amplification. These formulations typically contain a novolak resin, an acid generator, and a melamine crosslinking agent. The chemistry of such formulations has been previously described. An evaluation of OCG LMB-7011, an acid catalyzed chemically amplified negative i-line resist, has been conducted with the CORE-2564. This resist can be processed similarly to OCG-895i in standard mask process equipment, except that a post exposure bake is required to crosslink the exposed resist. With wet chrome etching, this resist exhibits exposure latitude similar or better than OCG-895i, benefiting from the fact that over-exposure is required to compensate for etch undercut when using a negative resist. Sub-micron resolution has been achieved with good linearity. CD control is marginal, due to a strong CD sensitivity to PEB temperature. A modified PEB process demonstrates improved CD control.