Schott Researchers Develop New Phase-Shift Material

Anne L. Fischer

A research and development team in Meiningen, Germany, has developed an advanced phase-shift material for Schott Lithotec AG of Jena, Germany. The material is suitable for 157-, 193- and 248-nm lithography, such as for use in DRAM memory and logic applications.

Mask blanks offer the ability to independently adjust phase and transmission for specific applications in 157-, 193- and 248-nm lithography.

As feature sizes on semiconductor integrated circuits have shrunk, the wavelength used in the lithographic patterning of those features has become increasingly important. Schott's material features tantalum and silicon-dioxide layers rather than molybdenum silicide. The thickness of two layers can be fine-tuned for the desired lithography wavelength and transmission value, which defines the resolution and the minimum feature size that can be printed on a wafer.

Günter Hess, R&D manager at Schott Lithotec, said that the material makes the wafer fabrication process more productive and that it yields more reliable devices because it is designed for specific applications. For example, if a 10-nm-thick tantalum layer is needed to act as a reliable etch stop, a maximum transmission of 28 percent for 157- and 193-nm and 30 percent for 248-nm wavelengths can now be achieved.