Shin-Etsu produces quartz substrates that demonstrate excellent permeability and low thermal expansibility in the far-ultraviolet range. Shin-Etsu quartz substrates are most commonly used as photomask substrates for optical lithography and other applications that require ultra-high purity and high precision polished substrates. As far as polished substrates are concerned, quartz substrates have an advantage over regular glass substrates because they offer much better light transmission and thermal resistance over their counterparts.