X-Ray Lithography for Integrated Circuit Development and Manufacturing

X-ray lithography is a technology which has been waiting for a problem to solve that is tougher than its own problems. Development of X-ray lithography dates from the early 1970's [1]--[3] and since that time, improvements in resolution of optical and near UV projection aligners and step-and-repeat systems have kept pace with processing ability for fabrication of smaller components in silicon integrated circuits (IC's). However, 1 µm or smaller features are now a design requirement for semiconductor integrated circuits (SIC's) which will have a significant performance advantage over current manufacture [4], [5]. In addition practical means for fabricating high quality X-ray masks have been found [6] along with sensitive resists and resist systems which are designed for reactive ion etching (RIE) processes [7], [8]. Reliable, economical, and long-lived X-ray sources have also been developed, [9], thus enabling us to design and build X-ray exposure tools for SIC and other fabrication. In this paper the X-ray lithography system developed at Bell Laboratories will be described along with evaluation of its use in a laboratory SIC fabrication facility. Projections for future developments in X-ray lithography will be given.