Apparatus and method for photomask design
AssigneeCadence Design Systems, Inc.
InventorsAbdurrahman Sezginer, Roy Prasad, Chi-Song Horng, Hsu-Ting Huang
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Abstract
An apparatus and method of synthesizing a photolithographic data set includes using a first computational model to calculate a first figure-of-merit for the photolithographic data set; changing a first part of the photolithographic data set to increase the first figure-of-merit; and then using a second computational model to calculate a second figure-of-merit of the photolithographic data set; and changing a second part of the photolithographic data set to increase the second figure-of-merit. The second computational model enables figure-of-merit calculations to be executed at a significantly faster execution rate than the first computational model.
Claims33
A method operating on a computer of synthesizing a photolithographic data set comprising:
- partitioning by using the computer the photolithographic data set into a first part and second part based on criticality, wherein the photolithographic data set provides a target pattern that produces a wafer pattern, the wafer pattern is calculated at a given dose and defocus condition, and the first part is more critical than the second part;
- using a first computational model to calculate a first figure-of-merit of the first part, wherein the first figure-of-merit is a measure of a first difference between sections of the target pattern and the wafer pattern that correspond to the first part;
- changing the first part of the photolithographic data set to increase said first figure-of-merit;
- using a second computational model to calculate a second figure-of-merit of the second part, wherein the second computational model executes faster than said first computational model, and the second figure-of-merit is a measure of a second difference between sections of the target pattern and the wafer pattern that correspond to the second part;
- and
- changing the second part of the photolithographic data set to increase the second figure-of-merit;
- wherein the photolithographic data set corresponds to position-dependent variations in an optical refractive index n(x, y, z) of at least a part of a photomask;
- and
- wherein said operation of using a first computational model to calculate a first figure-of-merit of the photolithographic data set includes:
- using said first computational model to calculate a scattering of illuminating electromagnetic waves using a coupled wave analysis, a boundary integral equation, a finite-elements method, a finite-difference method, or a thin-film interference method.
A method operating on a computer of synthesizing a photolithographic data set, comprising:
- partitioning by using the computer the photolithographic data set into a first part and second part based on criticality, wherein the photolithographic data set provides a target pattern that produces a wafer pattern, the wafer pattern is calculated at a given dose and defocus condition, and the first part is less critical than the second part;
- using a first computational model to calculate a first figure-of-merit of the first part, wherein the first figure-of-merit is a measure of a first difference between sections of the target pattern and the wafer pattern that correspond to the first part;
- changing the first part of the photolithographic data set to increase said first figure-of-merit;
- using second computational model to calculate a second figure-of-merit of the second part, wherein the second figure-of-merit is a measure of a second difference between sections of the target pattern and the wafer pattern that correspond to the second part;
- changing a second part of the photolithographic data set to increase the second figure-of-merit;
- wherein the photolithographic data set corresponds to position-dependent variations in an optical refractive index n(x, y, z) of at least a part of a photomask;
- and
- wherein said operation of using a second computational model to calculate a second figure-of-merit of the photolithographic data set includes:
- using said second computational model to calculate a scattering of electromagnetic fields using a coupled wave analysis, a boundary integral equation, a finite-elements method, a finite-difference method, or a thin-film interference method.
Dependencies are inferred from the claim text.