A Strategic Optical Lithography for Below 0.25 Micron Design Rules.

Abstract

Semiconductor device fabrication costs are dramatically escalating each year. Almost lithographers suffer from a paradox; Which lithography will best meet the technical and economic needs of VLSI manufacturing in the drive toward below 0.25 micron design rules?. This paper gives an outline of the possibility and strategy of optical lithography with productivity and cost efficiency for the development and production of 0.25micron design rule devices and beyond on the basis of our recent development results.To control costs, lithography will continue to push the extension of optical lithography as far as it can go. In the lithography for 256MbDRAMs production, a capability of 0.20micron lithography resolution is required. We have developed a new chemically amplified positive resist with high stability and an excimer laser based stepper with high alignment accuracy and off-axis illumination for KrF excimer laser lithography as a state-of-the art on shorter wavelength. The solution of 256MbDRAMs lithography is a complementary strategy employing both i-line for non-critical layers and KrF excimer laser for critical layers in order to achieve the lowest manufacturing cost.Sub-quarter micron feature size is required to lithography for the development of 1Gbit DRAMS. In order to break-through below 0.20micron barrier of optical lithography, ArF excimer laser lithography, which is a super state-of-the-art, has been challenged and developed. The challenges are constructed of the projection system installing a refractive achromatic aspherical 4X lens and a suitable resist material with high transparency. It is expected not only as the next significant technology but also as the final optical lithography to produce next generation VLSI. The strategy of optical lithography will be a endless development for semiconductor industries.