A Vertical X-ray Stepper for SOR Lithography

Abstract

A vertical x-ray stepper for SOR lithography has been developed. The stepper exposes wafers in a normal atmosphere to vertically-scanned SOR with continuous alignment control during exposure. The key devices of the stepper are a vertical X-Y stage and an opticalheterodyne alignment system. The X-Y stage uses airlubricated components, including air bearing lead screws, linear sliders and radial/thrust bearings. The optical-heterodyne alignment system detects the displacement between the mask and wafer gratings with precision of 8.3nm. Several exposure experiments proved that the alignment capability is better than ±0.1μm for a 3σ-value.

Overcoat Processing Technique for a Highly-sensitive Chemically Amplified Positive X-ray Resist.

“…X-ray exposure was carried out in air using an SR lithography system including the Super-ALTS SR source and the SS-2 aligner. [10,11] The resist was then post-exposure baked at 85oC for 120 seconds, followed by the strip of overcoats using the same solvent as that used for the initial coating. Finally, the resist was developed in a 0.23 N tetramethyl ammonium hydroxide aqueous solution.…”