Patent ID: 7378195

Claim:
A method of designing an alternating phase shifting mask for projecting an image of an integrated circuit design comprising: providing coloring rules for assigning phases to phase shifting shapes of an alternating phase shifting mask; providing a first cell comprising at least one phase shifting shape assignable to a first phase and at least one phase shifting shape assignable to a second phase opposite to the first phase, at least one of the phase shifting shapes being adjacent to an edge of the first cell, wherein all phase shifting shapes within said first cell are binary colorable according to said coloring rules; providing a second cell comprising at least one phase shifting shape assignable to a first phase and at least one phase shifting shape assignable to a second phase opposite to the first phase, at least one of the phase shifting shapes being adjacent to an edge of the second cell, wherein all phase shifting shapes within said second cell are binary colorable according to said coloring rules; assigning phases to the phase shifting shapes of the first and second cells; juxtaposing an edge of the first cell along an edge of the second cell such that the phase shifting shapes adjacent the respective first and second cell edges are adjacent each other; after juxtaposing the edge of the first cell along the edge of the second cell, determining any spacing between the adjacent phase shifting shapes in the first and second cells; determining any difference in phase between the adjacent phase shifting shapes in the first and second cells; if the adjacent phase shifting shapes in the first and second cells lie less than a predetermined minimum spacing required for system resolution, and if such adjacent phase shifting shapes are of opposite phase, reversing the phase of the phase shifting shapes in one of the first and second cells such that the adjacent phase shifting shapes are of the same phase; if the adjacent phase shifting shapes in the first and second cells are greater than the predetermined minimum spacing but less than a spacing whereby there is no interaction of transmitted light between phase shapes, inserting a dummy space between the phase shifting shapes; and creating a cell array comprising the first and second cells arranged so that said array is colorable in accordance with said coloring rules while preserving the binary colorability of said first and second cell.