System and method for calibrating a lithography model
First Claim
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1. A method for calibrating a model of a photolithography process, comprising:
- providing a computational model of a photolithography process, the computational model having an adjustable parameter;
printing a first pattern with the photolithography process as a printed pattern;
measuring an aspect of the printed pattern;
using the computational model to calculate an image intensity at a location determined according to the measured aspect;
minimizing a first cost function that comprises a first difference between the calculated image intensity and an intensity threshold;
calculating a second cost function comprising a second difference between a measured critical dimension of the printed pattern and a critical dimension simulated by the computational model;
minimizing the first cost function with respect to a model parameter;
determining if the computational model predicts that a portion of a first pattern will not print;
removing from a definition of the second cost function, the critical dimension of the portion of the first pattern that will not print; and
minimizing the second cost function with respect to the model parameter.
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Abstract
The present invention provides a method for calibrating a computational model of a lithography process by calculating a demerit function using an intensity measurement at a location of a wafer; and calibrating the lithography model or a mask making model by determining values of parameters of the computational model using the calculated demerit function. The method may also use a second demerit function that is defined by the sum of squares of differences between a simulated and measured critical dimensions of a feature on the wafer.
38 Citations
15 Claims
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1. A method for calibrating a model of a photolithography process, comprising:
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providing a computational model of a photolithography process, the computational model having an adjustable parameter; printing a first pattern with the photolithography process as a printed pattern; measuring an aspect of the printed pattern; using the computational model to calculate an image intensity at a location determined according to the measured aspect; minimizing a first cost function that comprises a first difference between the calculated image intensity and an intensity threshold; calculating a second cost function comprising a second difference between a measured critical dimension of the printed pattern and a critical dimension simulated by the computational model; minimizing the first cost function with respect to a model parameter; determining if the computational model predicts that a portion of a first pattern will not print; removing from a definition of the second cost function, the critical dimension of the portion of the first pattern that will not print; and minimizing the second cost function with respect to the model parameter. - View Dependent Claims (2, 3, 4, 5)
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6. A computer program product having instructions embedded in a non-transitory computer useable medium, the instructions configured to cause a processor to perform the operations of:
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providing a computational model of a photolithography process, the computational model having an adjustable parameter; printing a first pattern with the photolithography process as a printed pattern; measuring an aspect of the printed pattern; using the computational model to calculate an image intensity at a location determined according to the measured aspect; minimizing a first cost function that comprises a first difference between the calculated image intensity and an intensity threshold; calculating a second cost function comprising a second difference between a measured critical dimension of the printed pattern and a critical dimension simulated by the computational model; minimizing the first cost function with respect to a model parameter; determining if the computational model predicts that a portion of a first pattern will not print; removing from a definition of the second cost function, the critical dimension of the portion of the first pattern that will not print; and minimizing the second cost function with respect to the model parameter. - View Dependent Claims (7, 8, 9, 10)
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11. A computer-aided design tool configured to calibrate a model of photolithography process, comprising:
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a processor; a memory connected to the processor; and a non-transitory computer readable medium having instructions embedded therein, the instructions configured to cause the processor to perform the operations of; providing a computational model of a photolithography process, the computational model having an adjustable parameter; printing a first pattern with the photolithography process as a printed pattern; measuring an aspect of the printed pattern; using the computational model to calculate an image intensity at a location determined according to the measured aspect; minimizing a first cost function that comprises a first difference between the calculated image intensity and an intensity threshold; calculating a second cost function comprising a second difference between a measured critical dimension of the printed pattern and a critical dimension simulated by the computational model; minimizing the first cost function with respect to a model parameter; determining if the computational model predicts that a portion of a first pattern will not print; removing from a definition of the second cost function, the critical dimension of the portion of the first pattern that will not print; and minimizing the second cost function with respect to the model parameter. - View Dependent Claims (12, 13, 14, 15)
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Specification