Pellicle Mount is the process of attaching a thin transparent membrane (pellicle) over the patterned mask surface — the pellicle protects the mask pattern from contamination particles, keeping any particles that land on the pellicle out of the lithographic focal plane so they don't print as defects.

Pellicle Details

• Membrane: Thin polymer (DUV: ~800nm thick) or inorganic (EUV: polysilicon, SiN, CNT) membrane stretched over a frame.
• Frame: Aluminum or stainless steel frame bonded to the mask — defines the standoff distance.
• Standoff: ~6mm gap between pellicle and mask surface — particles on the pellicle are defocused and don't print.
• Transmission: >99% transmission at the exposure wavelength — minimal impact on dose and uniformity.

Why It Matters

• Contamination Protection: Without a pellicle, a single particle on the mask can print on every wafer — catastrophic yield loss.
• EUV Challenge: EUV pellicles must survive 250W+ EUV power — extreme thermal and radiation requirements.
• Lifetime: Pellicles degrade over time (haze, transmission loss) — lifetime limits mask usage.

Pellicle Mount is the mask's protective shield — a transparent membrane that keeps contamination particles from printing as defects on wafers.