Corning Incorporated announces two of its scientists received a patent for a glass that enables the transmission of wavelengths at 157nm. The silica glass will be used to create photomasks for microlithography applications. A photomask is a transparent optic used in microlithography that contains the information written on integrated circuits.

Dr. Lisa Moore and Dr. Charlene Smith, both scientists within Corning's Semiconductor Materials Division, modified the composition of silica by removing the water and adding fluorine ions. The resulting glass enables the transmission of wavelengths in the vacuum ultraviolet, particularly 157 nm, a wavelength the semiconductor industry thought was impossible to achieve with silica glass material.

"Before we announced our work a couple of years ago, the industry had almost written off 157 nm lithography because there wasn't a photomask to support it," said Smith. "We were able to prove to the industry and to our customers that silica can be transmissive enough to be used for next generation microlithography applications."

The challenge Moore and Smith faced was finding a material with the appropriate transmission and other desirable properties, such as low thermal expansion, necessary to withstand exposure to vacuum ultraviolet light at 157 nm.
"We recognized that the component in silica that limits transmission at very short wavelengths is the OH, or water content," said Moore. "By removing the water and adding fluorine to the material, we were able to create a glass that is transmissive at the shorter wavelengths, which is necessary to move forward with 157nm microlithography."

Corning's push to develop this new silica glass is in response to the semiconductor industry's trend toward the miniaturization of electronic devices. When used in 157 nm microlithography applications, this material will enable smaller features to be printed on integrated circuits.