This paper describes process technologies for an x‐ray mask using Ta as the x‐ray absorber and as the x‐ray membrane. can be grown heteroepitaxially in a coldwall LPCVD reactor at 1000°C and 3.5 torr using a gas mixture of , , and . has a stress of and a Young's modulus of . Pure Ta with Ar ions implanted by 150 keV is more stable and dense than Ta alloys and their nitrides. The film density is about 16 g/cm3 and the stress change due to annealing of 200°C is below . The yield of stress control is 68% for . The temperature of the membrane during Ta RIE is controlled by He cooling from the back. It is held between 45° and 100°C at a power density of 0.8 W/cm2. A mixture of and (1:1) is used as the etching gas. The gas pressure is from 0.18 to 0.2 torr. The etch rate of Ta is 1.2 μm/min and the selectivity of Ta to a resist (AMS‐1) is 7. A 0.8 μm thick Ta pattern of 0.15 μm lines and spaces is obtained by using a 0.5 μm thick single‐layer resist. Electron beam lithography on a thin membrane requires a high‐contrast resist (AMS‐1) and a well‐controlled correction of the proximity effect because of the high electron backscattering on Ta. Si etchback is done by spray etcher using a mixture of and (1:3) with a high speed of 8 min per mask. The total fabrication process is designed to minimize mask distortion. The maximum mask distortion due to the absorber stress is 0.11 μm (3σ) including the measurement errors of Nikon 2 I . The mask used for the measurement had a circular membrane of 60 mm diam and a field window. The was 2 μm thick and the Ta was 0.8 μm thick with a stress of .