Diamond membranes are being developed for x-ray lithography masks. Typically these 1-3 im thick membrane films are deposited on Si substrates using microwave driven plasmas. To obtain smooth films with uniform tensile stress spray and electrophoretic deposition of 0. 1 zm diamond seeds were used to control the initial nucleation and growth of the diamond films. The films have a room ternperature tensile stress of 25-125 MPa. The temperature dependence of the stress is due to the tensile growth stress of the diamond film and the thermal stress of the diamond-Si layer structure. The films have a biaxial modulus of 800 GPa. X-ray lithography masks have been made and used to print patterns with x-rays from a synchrotron source. 1 .