X-ray lithography for VLSI

In order for any lithography to become the preferred technique for the production of very large scale integrated circuit (VLSI) devices, the technique will have to 1) achieve the required resolution and registration and 2) become more cost effective in this capacity for large volume production than its competitors. The advent of advanced lithographic techniques for LSI production has been postponed by substantial advances in conventional lithography. However, integrated circuits with feature sizes of 1 µm or smaller seem to have significant performance and price advantages over current devices. Such submicron feature sizes press noncontact optical lithography up against the laws of physics. Meanwhile, advances in X-ray lithography have occurred and continue to occur at a promising rate. This paper discusses our experience with X-ray lithography at Intel. Most of our X-ray experience is with the Intel 1-Mbit bubble memory because of the small minimum feature size (1.2 µm) and the defect and alignment tolerance of this device. However, this discussion will be geared toward general VLSI applications of X-ray lithography.