Method and apparatus for correcting 3D mask effects

A computer-readable storage medium storing instructions that when executed by a computer cause the computer to perform a method for improving lithography performance by correcting for 3D mask effects, the method comprising:

• receiving a mask layout that contains etched regions, called shifters, that can have a phase shift relative to other regions;
• choosing a shifter in the mask layout;
• correcting for 3D mask effects by, iteratively,
• selecting a region within the shifter,
• adjusting the phase shift of the selected region in a simulation model to account for 3D mask effects, and
• modifying the shape of the shifter based on the difference between a desired pattern and a simulated pattern generated using the simulation model.

An apparatus for improving lithography performance by correcting for 3D mask effects, the apparatus comprising:

• a receiving mechanism configured to receive a mask layout that contains etched regions, called shifters, that can have a phase shift relative to other regions;
• a choosing mechanism configured to choose a shifter in the mask layout;
• a correcting mechanism configured to correct for 3D mask effects by, iteratively,
• selecting a region within the shifter,
• adjusting the phase shift of the selected region in a simulation model to account for 3D mask effects, and
• modifying the shape of the shifter based on the difference between a desired pattern and a simulated pattern generated using the simulation model.