Abstract
In ASET, in cooperation with NTT, we have developed key systems for X-ray lithography (XRL) such as X-ray steppers and a 100-kV electron-beam (EB) lithography system for x-ray mask fabrication. Mask-to-mask overlay accuracy within 20nm (3σ) between the gate- and contact-hole-layers for 1-Gb DRAM has been achieved. Critical dimension (CD) control of ±14nm for the gate and ±10nm for the contact-hole-patterns have also been realized. The advantages of XRL over advanced optical lithography, in terms of both resolution and process latitude, were demonstrated through computer simulation. The outcomes of several experiments have convinced us that XRL is a particularly promising technology for mass-producing 0.1-μm or smaller devices.
