Editing Photomask (section)

==Pellicles==
The term "pellicle" is used to mean "film", "thin film", or "membrane." Beginning in the 1960s, thin film stretched on a metal frame, also known as a "pellicle", was used as a beam splitter for optical instruments. It has been used in a number of instruments to split a beam of light without causing an optical path shift due to its small film thickness. In 1978, Shea et al. at IBM patented a process to use the "pellicle" as a dust cover to protect a photomask or reticle. In the context of this entry, "pellicle" means "thin film dust cover to protect a photomask".

Particle contamination can be a significant problem in semiconductor manufacturing. A photomask is protected from particles by a pellicle{{spaced ndash}}a thin transparent film stretched over a frame that is glued over one side of the photomask.  The pellicle is far enough away from the mask patterns so that moderate-to-small sized particles that land on the pellicle will be too far out of focus to print.  Although they are designed to keep particles away, pellicles become a part of the imaging system and their optical properties need to be taken into account. Pellicles material are nitrocellulose and made for various transmission wavelengths. Current pellicles are made from polysilicon, and companies are exploring other materials for high-NA EUV and future chip making processes.<ref>{{Cite web | title=What Is High-NA EUV? - Breakfast Bytes - Cadence Blogs - Cadence Community | url=https://community.cadence.com/cadence_blogs_8/b/breakfast-bytes/posts/what-is-high-na-euv | access-date=2025-03-26 | website=community.cadence.com}}</ref><ref>{{cite journal|author=Chris A. Mack|date= November 2007|title=Optical behavior of pellicles|journal=Microlithography World|url=http://www.solid-state.com/display_article/311163/28/none/none/Feat/The-Lithography-Expert-Optical-behavior-of-pellicles|access-date=2008-09-13}}</ref>
[[File:Pellicle Mounting Machine MLI.jpg|right|thumb|Pellicle mounting machine MLI]]