US Patent 7685557 Radiation mask with spatially variable transmissivity

A mask, a method for creating a mask, and a method for irradiating a substrate through use of the mask. Creating the mask establishes the mask by designing the mask, forming the mask, or both designing and forming the mask. Creating the mask includes receiving a specified target transmittance (TS) of the substrate with respect to radiation propagated from a radiation source and transmitted through the mask with spatial selectivity in accordance with a spatially varying transmissivity (TM) of the mask with respect to the radiation. The mask is disposed between the radiation source and the substrate. The mask includes transparent portions and reflective portions distributed within the transparent portions. The first radiation after having passed through the mask is transmitted into the substrate in accordance with a spatially varying reflectance (R) of the substrate such that TM*(1−R) is about equal to TS.