Yoshiyuki Kawazu

Fabrication of X-Ray Mask Using W-CVD for Forming Absorber Pattern

Tungsten chemical vapor deposition (W-CVD) using WF6 and H2 as reactants was applied to forming absorbers of X-ray masks for synchrotron radiation (SR) lithography. For this purpose, the properties of deposited W (CVD-W), such as stress, density and thermal stability, were examined. The stress can be minimized reproducibly to less than 1×108 dyn/cm2 by controlling the flow rate of WF6 at various substrate temperatures. This W film was thermally stable up to 200°C, and the density was 18.5 g/cm3. From these results, CVD-W was found to be suitable as an absorber material. For the formation of absorber patterns, filling SiO2 grooves with stress-reduced CVD-W was examined. The 0.2-µm-wide grooves were filled with CVD-W and absorber patterns were formed by etch-back. The X-ray mask was successfully fabricated by this developed process.