At photomask manufacturing, post pellicle inspection suffers from an interference of pellicle size and height dimensions
with the inspection equipment requirements. This pellicle shadow causes nonreliable inspection results. The evolution
of this effect as well as similar potentially upcoming effects during other lithography processes need to be understood in
order to identify potential problems ahead of time and guide the industry accordingly. The study recommends
standardizing pellicle size and height dimensions in order to coordinate the required changes at scanner, mask inspection,
mask metrology and pellicle vendors in the near and long term. Since frequent changes in other pellicle properties are
expected over time to fulfill the requirements for high NA lithography and haze reduction, a standard in pellicle
dimensions will also help controlling the complexity of pellicle variations.
CD uniformity and CD mean to target specifications nowadays can only be accomplished by mask manufacturing process using chrome dry etch. Chrome plasma etch processes tend to show a strong dependency of the chrome etch rate and thus the etch bias on the clearfield percentage of a mask resulting in varying offtarget behavior. There are various possibilities to compensate for this loading effect. In previous work the methods of using exposure dose and development time for offtarget control were investigated. In this study we examined the capability of plasma etch parameters to be used for offtarget control. The effects of oxygen concentration, pressure and overetch percentage on etch bias and CD uniformity were experiment. Two different development processes were investigated. The resulting offtarget control model was then confirmed by running additional masks at three different clearfield percentages. Measurement results showed a high confidence level for the model predicted numbers. SEM images confirmed stable behavior of chromium sidewall angles.