Determining calibration parameters for a lithographic process

A computer-program product for use in conjunction with a computer system, the computer-program product comprising a non-transitory computer-readable storage medium and a computer-program mechanism embedded therein for determining a set of calibration parameters for use in a model of a photo-lithographic process, the computer-program mechanism including:

• instructions for receiving images of a test pattern, wherein the test pattern was produced using the photo-lithographic process, wherein the images include a first image at a first focal plane in an optical system, a second image at a second focal plane in the optical system, and a third image at a third focal plane in the optical system, and wherein the first focal plane, the second focal plane and the third focal plane are different;
• instructions for calculating a first set of calibration parameters associated with the first image, a second set of calibration parameters associated with the second image, and a third set of calibration parameters associated with the third image;
• and
• instructions for determining an interpolation function based on the first set of calibration parameters, the second set of calibration parameters, and the third set of calibration parameters, wherein the interpolation function provides the set of calibration parameters corresponding to an arbitrary focal plane in a photo-lithographic system that implements the photo-lithographic process;
• and
• wherein the set of calibration parameters are used in a set of transmission cross coefficients in the model of the photo-lithographic process.

A computer system, comprising:

• a processor;
• a memory;
• and
• a program module for determining a source pattern to illuminate a photo-mask during a photo-lithographic process, the program module stored in the memory and configured to be executed by the processor to determine a set of calibration parameters for use in a model of a photo-lithographic process, the program module including:
• instructions for receiving images of a test pattern, wherein the test pattern was produced using the photo-lithographic process, wherein the images include a first image at a first focal plane in an optical system, a second image at a second focal plane in the optical system, and a third image at a third focal plane in the optical system, and wherein the first focal plane, the second focal plane and the third focal plane are different;
• instructions for calculating a first set of calibration parameters associated with the first image, a second set of calibration parameters associated with the second image, and a third set of calibration parameters associated with the third image;
• and
• instructions for determining an interpolation function based on the first set of calibration parameters, the second set of calibration parameters, and the third set of calibration parameters, wherein the interpolation function provides the set of calibration parameters corresponding to an arbitrary focal plane in a photo-lithographic system that implements the photo-lithographic process;
• and
• wherein the set of calibration parameters are used in a set of transmission cross coefficients in the model of the photo-lithographic process.