Scientists from Corning Inc.(Corning, NY) have rceived a patent for a glass that enables the transmission of wavelengths at 157 nm. 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.
Lisa Moore and Charlene Smith, scientists within the firm'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 157nm, 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 hat 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 157nm. “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 157-nm 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.