Patent ID: 6957414

Claim:
A method for determining an ability to project images of integrated semiconductor circuits onto alternating dark-field phase masks and for determining possible phase conflicts, to project images of electrical circuit elements such as interconnects and similar items into transparent regions of a phase mask, which comprises the steps of: determining critical regions, a critical region being identified for each case in which a distance between two adjacent transparent regions provided for the phase mask falls below a specific predetermined minimum distance; determining overlap regions between straight sections of the critical regions and determining end regions of the straight sections of the critical regions, the end regions of the straight sections ending in a midst of the transparent regions; determining degenerate critical regions by subtracting the overlap regions from the critical regions; determining contiguous regions lying outside the transparent regions and the critical regions; determining outer boundaries for each of the contiguous regions, for each of the overlap regions and for each of the end regions; determining a number of stretches of contact with the degenerate critical regions for each of the outer boundaries determined for each of the contiguous regions, for each of the overlap regions and for each of the end regions; and determining a presence of a phase conflict if the number of stretches is an odd number for any of the outer boundaries.