Development of an EUV irradiation tool in hydrogen atmosphere to evaluate EUV mask absorber durability

Abstract In EUV lithography, residual hydrocarbon gas in a vacuum chamber causes carbon contamination of the mask and optics, resulting in a reflectance drop. To mitigate this issue, several pascals of hydrogen gas are introduced into the EUV scanner. In a hydrogen atmosphere, high-power EUV irradiation generates EUV-induced hydrogen plasma, which might destroy the absorber layer or Mo/Si multilayer of the EUV mask. This damage is called a “blister.” To evaluate the damage, a high-power EUV irradiation tool with hydrogen gas was installed at the BL09 beamline of the NewSUBARU synchrotron light facility. The durability of a normal TaBO/TaBN absorber on an EUV mask was evaluated. No blister occurred on this absorber at a high EUV dose of 2600 kJ cm −2 . The hydrogen ion dose was estimated as 1.3 × 10 14 ions s −1 by current and voltage measurements with an EUV intensity of 43 W cm −2 (89 mW) and hydrogen pressure of 70 Pa.