Abstract
The haze nucleation and growth phenomenon on critical photomask surfaces has periodically gained attention as it has
significantly impacted wafer printability for different technology nodes over the years. A number of process solutions
have been promoted in the semiconductor industry which has been shown to suppress or minimize the propensity for
haze formation, but none of these technologies can stop every instance of haze. Fortunately, a novel technology which
uses a dry (no chemical effluents) removal system, laser-based, through pellicle process has been reported recently. The
technology presented here avoids many of the shortcomings of the wet clean process mentioned previously. The dry
clean process extends the life of the photomask; maintains more consistent CD’s, phase, and transmission; avoids
adjustment to the exposure dose to account for photomask changes, reduces the number of required inspections and
otherwise improves the efficiency and predictability of the lithography cell.
We report on the performance of photomask based on a design developed to study the impact of metrology variations on
dry clean process. In a first step we focus on basic characteristics: CD variation, phase, Cr/MoSi transmission, pellicle
transmission, registration variations. In a second step, we evaluate haze removal and prevention performance and wafer
photo margin. Haze removal is studied on the masks for several haze types and various exposure conditions. The results
of this study show that some of metrology variation are likely to be a problem at high technology node, and haze removal
performance is determined whether the component of haze is remained or not after treatment.
