Optical scatterometry-based metrology is now widely used in wafer fabs for lithography, etch, and CMP
applications. This acceptance of a new metrology method occurred despite the abundance of wellestablished
CD-SEM and AFM methods. It was driven by the desire to make measurements faster and with
a lower cost of ownership. Over the last year, scatterometry has also been introduced in advanced mask
shops for mask measurements. Binary and phase shift masks have been successfully measured at all desired
points during photomask production before the pellicle is mounted. There is a significant benefit to
measuring masks with the pellicle in place. From the wafer fab's perspective, through-pellicle metrology
would verify mask effects on the same features that are characterized on wafer. On-site mask verification
would enable quality control and trouble-shooting without returning the mask to a mask house. Another
potential application is monitoring changes to mask films once the mask has been delivered to the fab (haze,
oxide growth, etc.). Similar opportunities apply to the mask metrologist receiving line returns from a wafer
fab. The ability to make line-return measurements without risking defect introduction is clearly attractive.
This paper will evaluate the feasibility of collecting scatterometry data on pelliclized masks. We explore
the effects of several different pellicle types on scatterometry measurements made with broadband light in
the range of 320-780 nm. The complexity introduced by the pellicles' optical behavior will be studied.