A novel EUV exposure station for nanotechnology studies

The soft X-ray region around 13 nm (Extreme Ultra Violet, EUV) has become very important for applications to nanopatterning. Typically, high-resolution patterning of less than 50 nm pitch lines and spaces requires optical systems that are complex and expensive. An appealing alternative is provided by interferometric patterning, whereby an EUV beam of relatively high degree of coherence is used to create a pattern by interfering two (or more) parts of the wavefront. Briefly, the radiation from a short undulator illuminates two gratings with pitch in the range of 40–100 nm. The first orders overlap, and in this region an interference pattern is generated with pitch half the original. This technique produces very high resolution 20–50 nm pitch patterns. Thus, in a collaborative effort involving CNTech and the SRC we have designed, constructed and tested a new beamline dedicated to nanopatterning using the radiation from a new undulator on the Aladdin storage ring. The beamline provides 210 mW/cm2 average in-band power flux to the endstation. We note that the beamline is designed to provide a relatively large area exposure, with good wavefront quality in intensity and phase. The endstation supports interferometric lithography techniques, with demonstrated patterning capability down to 40 nm pitch lines and spaces. In addition to nanopattering, a branch-line experimental station is designed for studying the photo-desorption from materials during exposure. The outgassing species are captured and transferred to a gas-chromatograph for off-line characterization. This paper describes the undulator source, the beamline, and the exposure stations.