Developing a soft X-ray projection lithography tool

The circuit-integration densities needed for semiconductor devices in the late 1990s will require advanced patterning technologies that can print line widths of 0.2 micrometers or less. Because it uses shorter wavelengths, X-ray lithography is one of the most promising methods for volume production of such circuits. X-ray projection lithography, which uses reflective optics, offers the added advantage of image reduction. AT&T Bell Laboratories has used X-ray projection lithography for diffraction-limited imaging with 140-angstrom radiation from a synchrotron. Now, Sandia National Laboratories and AT&T Bell Laboratories are developing a soft X-ray projection lithography tool that uses a compact source of X-rays: the laser-plasma source. A possible alternative to the expensive, complex synchrotrons, the laser-plasma source could influence the future commercialization of X-ray projection lithography. This paper describes soft X-ray projection lithography and our progress in combining projection optics at 140 angstroms with a laser-plasma source.