There is a simple algorithm to translate the dense contacts of a regular design into a well assigned two phases in this paper. Some of its basic variant applications and a procedure to detect the phase assignment errors for the whole chip layer to insure the whole chip phase assignment success are also included. The variant applications include to add the assist features and assign the phases between the main features and the assist features and the post rule bias consideration. This executable environment makes the alternating PSM easy to be applied in the bright field of the dense contact.
"Phase assignment for bright field of dense contact", Proc. SPIE 4754, Photomask and Next-Generation Lithography Mask Technology IX, (1 August 2002); doi: 10.1117/12.476940; https://doi.org/10.1117/12.476940