Patent ID: 8745551

Claim:
A computer-implemented method comprising: obtaining model coefficients representing optical behavior of a lithographic process for imaging a portion of a design layout onto a substrate using a lithographic projection apparatus comprising an illumination source and projection optics; obtaining model coefficients representing optical behavior of a reference lithographic process separate from the lithographic process to which the lithographic process is to be tuned, wherein tuning comprises matching the optical behavior of the lithographic process to the reference lithographic process; and tuning the lithographic process to the reference lithographic process by: defining a multi-variable cost function of a plurality of design variables that represent adjustable characteristics of the lithographic process, the cost function being defined in terms of a difference between the obtained model coefficients for the lithographic process and the reference lithographic process, wherein at least some of the design variables comprise adjustable characteristics of the projection optics; and reconfiguring, using a computer, the characteristics of the lithographic process by adjusting the design variables until a predefined termination condition associated with the cost function is satisfied.