157-nm lithography attracts chip makers

ASM Lithography (ASML; Veldhoven, The Netherlands), which has been prodding the industry toward 157-nm lithography, has announced that nine large semiconductor manufacturers have joined the company's 157-nm program. The new members include Motorola, Philips, Advanced Micro Devices, and Infineon. Using calcium fluoride optics made by Carl Zeiss (Oberkochen, Germany), ASML is spearheading a program to create a scanner capable of producing 70-nm features on 300-mm wafers.

The ASML program consists of two parts. First, an exposure tool will be developed that will be shipped to program members by the end of 2003. Second, a concurrent effort will be made to develop associated technology, including photoresists, reticles and reticle handling, and processes. This work will revolve around a prototype ministepper installed at IMEC (Leuven, Belgium) and will include the application of optical-enhancement techniques such as phase-shift masks and optical-proximity correction.

The push toward 157 nm would not be possible without the development of light sources and optical materials. Cymer Inc. (San Diego, CA) makes a lithographic fluorine excimer laser; the first was just sold to Ultratech. Lambda Physik (Fort Lauderdale, FL), which produces a similar light source, has sold its lasers to SVGL and ASML. High-quality calcium fluoride is being developed by Bicron (Solon, OH), Corning Inc. (Corning, NY), and others.

Much of the initial research on optical materials and coatings for 157-nm lithography has occurred at a test facility at Massachusetts Institute of Technology Lincoln Laboratory (Lexington, MA), where a group has been subjecting optics to 157-nm radiation over long periods of time to determine their lifetimes. It was here that fluorine-doped and OH-reduced fused silica was shown to be a viable material for photomask substrates.—John Wallace, Senior Editor