A method of generating a mask is provided that optimizes the placement and
shape of optical proximity correction (OPC) features such as scattering
bars. According to some aspects, the method includes model-based
techniques for determining where to place assist features within the
design, thereby eliminating the need for experienced mask designers to
perform OPC, and also substantially reducing the time required to
determine an acceptable OPC solution. According to further aspects, the
method provides an OPC assist feature placement technique that enhances
the resulting depth of focus even when imaging features have dimensions
on the order of a quarter of the wavelength of the imaging system.