Rule optimization in lithographic imaging based on correlation of functions representing mask and predefined optical conditions

摘要

Methods, computer program products and apparatuses for optimizing design rules for producing a mask are disclosed, while keeping the optical conditions (including but not limited to illumination shape, projection optics numerical aperture (NA) etc.) fixed. A cross-correlation function is created by multiplying the diffraction order functions of the mask patterns with the eigenfunctions from singular value decomposition (SVD) of a TCC matrix. The diffraction order functions are calculated for the original design rule set, i.e., using the unperturbed condition. ILS is calculated at an edge of a calculated image of a critical polygon using the cross-correlation results and using translation properties of a Fourier transform. Once an optimum separation is calculated, it is incorporated into the design rule to optimize the mask layout for improved ILS throughout the mask.

主权项

1. A method implemented by a computer of optimizing an initial design rule into an updated design rule for producing a mask layout to be imaged by a lithographic apparatus, the method comprising:
selecting an initial design rule that specifies a minimum separation between features in the mask layout; selecting an autocorrelation function associated with a predefined optical condition of the lithographic apparatus; selecting respective mask transmittance functions for at least two features separated from each other by a distance in the mask layout; determining, using the computer, a change in illumination intensity at locations of a wafer plane associated with the at least two features as a function of perturbation of the distance between the at least two features, wherein a mathematical function for determining the change in illumination intensity per perturbation of the distance is derived using the mask transmittance functions and the autocorrelation function; and updating the initial design rule to generate the updated design rule specifying a new minimum separation between features by optimizing the change in illumination intensity to identify an optimal perturbation of the distance between the at least two features.