SBIR Phase II: A Simple and Practical Solid-State 157nm and 193nm Coherent Light Source for Applications in Lithography Development

This SBIR Phase II project will develop a new generation of fully-coherent, solid-state, vacuum-Ultraviolet (UV) light sources at 157nm and 193nm, to support the next generation of semiconductor fabrication and metrology, as well as for applications in basic research. Currently available UV excimer sources have limitations such as poor spatial coherence, making them unsuitable for metrology. Therefore, the most promising route to generate fully-spatially-coherent VUV sources is to up convert light from the visible-infrared region of the spectrum, where coherent laser sources already exist. However, a significant technical obstacle towards this goal is the lack of reliable solid-state nonlinear-optical crystals that work in the deep-UV. Unavoidable residual absorption at wavelengths <200nm can lead to long-term damage of nonlinear optical crystals, requiring constant replacement. Furthermore, for frequencies <193nm, no suitable nonlinear optical crystal currently exists. Therefore, gaseous nonlinear-optical media are an attractive alternative to crystals for generating light at wavelengths <200nm. This SBIR Phase II project will use four-wave mixing in gas filled hollow waveguides to develop a tabletop VUV laser capable of generating 10's of mW, and possibly 100's of mW of light at 157nm and at 193nm, in a fully coherent beam, at the very high (10kHz) repetition rates necessary for applications in metrology. This project has the potential to have a very broad impact on the semiconductor and electronics industries, as well as in basic science. Progress in both the complexity and the speed of microprocessors, DRAM memory, and other integrated electronics has been driven by the ability to make increasingly dense IC's, with ever-smaller feature sizes. This has been enabled by the development of higher-resolution lithographic "steppers" and the use of ever-shorter wavelengths of light for lithography. Because no bright, tabletop, sources currently exist, most short-wavelength materials, nano- and chemical science must take place at synchrotron sources, where access is limited and the sources are not optimized. Therefore, significant gains in productivity could occur with the availability of such a source.