A process for the fabrication of an X-ray absorbing mask includes providing a silicon substrate (10) having a front surface (16) and a back surface (18). A membrane layer (12) is formed on the front surface (16). In one embodiment of the invention, an etch stop layer (14) and an X-ray absorbing layer (20) are sequentially formed over the membrane layer (12). In a preferred embodiment, the X-ray absorbing layer (20) is tantalum silicon nitride deposited by RF sputter deposition directly onto the layers overlying the silicon substrate (10). The structure is then annealed at a temperature sufficient to reduce the internal stress in the X-ray absorbing layer (20). Finally, the X-ray absorbing layer is patterned to form a masking pattern (30, 36) on the membrane layer (12).