Pellicle
Beginner
A thin, clear film held just above a stencil’s pattern. Dust lands on the film, where it is blurry and doesn’t print.
Novice
A transparent film on a frame glued over one side of a photomask (the stencil for one chip layer). Dust that lands on it sits far enough from the pattern to be out of focus, so it doesn’t print onto the wafer.
Expert
Mounted after the mask’s final clean and inspection. An EUV pellicle is much harder to build than a deep-UV one: EUV masks reflect rather than transmit, so the 13.5 nm light crosses the pellicle twice, and the film has to let enough of it through while surviving the heat it absorbs.