Chemically Amplified Resist for Micromachining Using X-Ray Lithography

Abstract

New-generation Chemically Amplified Resists (CARs) such as the positive tone commercial UVIII resist offer a substantial gain in sensitivity, resolution, and process efficiency in deep ultraviolet, electron-beam, and x-ray lithographies. These characteristics are useful for the fabrication of structures for MEMS applications. In this work, the UVIII resist is characterised for x-ray lithographic applications by studying the “deprotection” or acid generation-diffusion process of the resist under different conditions of poste-xposure bake temperature and time, and of x-ray exposure time or dose. The x-ray irradiation from an aluminium anode at the wavelength of 0.83 nm was at an intensity of 45 μW/cm² on the resist surface. The deprotection process of the resist during post-exposure bake was monitored by using Fourier Transform Infrared (FTIR) spectroscopy. Results showed that the performance of UVIII could be optimised at the post-bake temperature of 140^oC and time of 2 minutes, and x-ray exposure dose of 18 mJ/cm². The results were confirmed by Scanning Electron Microscopic (SEM) studies on UVIII test structures, which were processed using the optimised condition. Test structure as small as 150 nm was obtained in 7 μm thick UVIII resist layer.