Polycrystalline diamond films for X-ray lithography mask

Uniform, good quality, low surface roughness and large-area polycrystalline diamond films were successfully synthesized with reasonable deposition rates using a microwave-plasma chemical-vapor-deposition system. Polycrystalline diamond membrane masks, fabricated for X-ray lithography membranes on 4″-diameter silicon wafers using an alternative fabrication process, have been evaluated for their stability exposed to a 60 mW cm−2 X-ray irradiation. In this study, it was found that methane concentration would affect quality, stress and surface roughness of polycrystalline diamond films. These properties will also influence the optical transmittance of diamond membranes. The optical transmittance of the polycrystalline diamond membrane was up to 60% at the wavelength of 633 nm and up to 70% at the wavelength of 800 nm. After X-ray irradiation, the quality of the polycrystalline diamond membrane was improved, and the optical transmittance of the polycrystalline diamond membrane increased by approximately 3%. From the Raman spectra analysis, it was suggested that a part of the non-diamond carbon have been transformed into diamond after the X-ray irradiation.