pellicle mount

**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.