Abstract

In the last fifteen years, the density of integrated circuits has increased at a steady rate. The lithography needed to do this has mainly relied on the development of optical systems with increasingly larger numerical apertures (N.A.) rather than on a reduction of wavelength. However, at the presently used wavelengths, this method of increasing the N.A. cannot be extended beyond critical dimensions (C.D.) of about 0.7 μm. Consequently, if the trend towards higher density is to continue, microlithography systems using shorter wavelengths will be needed. Indeed, work is now being done using the mercury I line (365 nm) and with excimer lasers at even shorter wavelengths (248 nm and 193 nm) as sources. These sources could allow lithography with C.D.'s somewhat below 0.5 μm.

© 1988 Optical Society of America