Preliminary evaluation of a laser-based proximity x-ray stepper

This paper reports on the initial lithographic evaluation of a commercial 1:1 proximity stepper that uses a laser-based plasma x-ray source. Our preliminary tests have shown that 0.4- and 0.5-mu-m lines and spaces can be printed consistently on Si wafers using a positive resist, which has a sensitivity of 6-10 mJ/cm2. Features smaller than 0.4-mu-m can be obtained, but the overlay accuracy of this system is targeted at 0.5-mu-m design rules. The 3-sigma spread in linewidth is greater than 0.05-mu-m, however, the stepper contribution must be separated from the resist processing issues, reticle critical dimension variations, and scanning electron micrograph measurement precision.