Patent ID: 8537444

Claim:
A method for designing a mask implemented for fabricating a hologram structure in a photosensitive layer of a semiconductor stack and for generating an optimized wavefield for illuminating said hologram structure to achieve a specified image target comprising alternating bright and dark pattern region in a photosensitive material layer of said stack, said method comprising: selecting a preliminary wave field and hologram diffractive properties using a scalar model at an artificially reduced spatial frequency wavelength; implementing wavefront engineering method to generate a physical structure for said hologram in a preliminary solution and a 1 st stage wave field for modulating said hologram; implementing local optimization to provide an optimized design for said hologram and a wavefront at the artificially decreased wavelength; incrementing the wavelength in a small upward increment; refining, at said incremented wavelength, said local optimization to tune in a solution for the current incremented wavelength by adjusting variables of a hologram profile, an index of the hologram features and a film stack beneath the hologram; and, iterating between said wavelength incrementing and refining to arrive at a solution which is valid at an operating wavelength, said solution including a 2 nd stage wave field for modulating said hologram, wherein a spatial frequency modulation in a resulting image includes the same bright and dark regions as the image target; and, generating a pair of lithographic masks suitable to generate 1 st stage and 2 nd stage wave fields at respective first and second sets of spatial frequencies using said wavefront engineering method.