Thin tantalum silicon composite film formation and annealing for use as electron projection scatterer

A thin transition-metal based scattering layer of a mask blank for use in EPL systems is formed by providing the thin transition-metal scattering layer directly over membrane layers on a lot of substrates, thereby forming a continuous contact between the single transition metal-based scattering layer and the membrane layer. Preferably, the single transition metal-based scattering layer is a single tantalum-silicon composite scattering layer having a stoichiometry of TaxSi. The deposition parameters for depositing the thin transition-metal based scattering layer are adjusted to provide the scattering layer uniformly over all substrates within the lot. A first substrate from the lot of substrates is then selected, an initial stress measurement of the scattering layer is determined and then the substrate is annealed at a first temperature. The stress of the scattering layer over the first annealed substrate is determined, and subsequently the anneal temperature is adjusted based on a comparison between the pre-anneal, initial stress measurement and the post-annealed stress measurement. A second substrate from the lot of substrates is then selected, annealed at the adjusted temperature, stress measurement of the scattering layer of the second substrate is determined, and the anneal temperature may once again be adjusted. The above process is repeated until a targeted stress level of the thin transition-metal based scattering layer of the mask blank has been obtained. The thin scattering layer is adapted to have final film stress controllable to within ±10% of the targeted stress.