Abstract

The fabrication of microelectronic devices with 0.35-μm and 0.25-μm resolution is widely expected to be accomplished with photolithogaphic techniques employing deep-UV radiation, mainly 248-nm and 193-nm lasers. A major area of concern at these wavelengths is the availability of high-quality, radiation-insensitive refractive optical materials and thin films. In addition to meeting stringent requirements in areas such as index homogeneity, these materials must be transparent at the operating wavelength and must be unchanged by prolonged irradiation, in particular with pulsed lasers. This paper will review the phenomenology of radiation-induced defect formation in fused silica, crystalline fluorides, and multilayer dielectric coatings and will address the effects of material impurities and processing conditions. The useful lifetime of the optical components is determined by an interplay between the optical design, quantitative analysis of radiation- induced effects, photoresist sensitivity, and required wafer throughput. It is shown that with the appropriate choice of materials and design, photolithographic systems can be kept within performance specifications for over 10 years of full-time operation.

© 1992 Optical Society of America