System and method for creating a focus-exposure model of a lithography process
First Claim
1. A computer-implemented method for creating a model of a lithography process having a process window, comprising:
- defining a set of model parameters and a set of fitting parameters having variable values for the model, the set of model parameters defining a parameter space;
obtaining a calibrated model by analyzing, using the computer, the model parameters and fitting parameters at a plurality of sampling locations within the process window, the plurality of sampling locations being a discrete subset of all possible process conditions within the process window, the calibrated model including values of the set of fitting parameters;
identifying a selected location in the process window that is different from any of the sampling locations; and
generating the model for the selected location using the calibrated model by varying the model parameters in accordance with the selected location while keeping the fitting parameters constant.
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Abstract
A system and a method for creating a focus-exposure model of a lithography process are disclosed. The system and the method utilize calibration data along multiple dimensions of parameter variations, in particular within an exposure-defocus process window space. The system and the method provide a unified set of model parameter values that result in better accuracy and robustness of simulations at nominal process conditions, as well as the ability to predict lithographic performance at any point continuously throughout a complete process window area without a need for recalibration at different settings. With a smaller number of measurements required than the prior-art multiple-model calibration, the focus-exposure model provides more predictive and more robust model parameter values that can be used at any location in the process window.
42 Citations
21 Claims
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1. A computer-implemented method for creating a model of a lithography process having a process window, comprising:
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defining a set of model parameters and a set of fitting parameters having variable values for the model, the set of model parameters defining a parameter space; obtaining a calibrated model by analyzing, using the computer, the model parameters and fitting parameters at a plurality of sampling locations within the process window, the plurality of sampling locations being a discrete subset of all possible process conditions within the process window, the calibrated model including values of the set of fitting parameters; identifying a selected location in the process window that is different from any of the sampling locations; and generating the model for the selected location using the calibrated model by varying the model parameters in accordance with the selected location while keeping the fitting parameters constant. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A computer-implemented method for generating a model of a lithography process capable of simulating the lithography process over a process window, the model having a set of model parameters that define a parameter space, the method comprising:
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identifying a set of test patterns; analyzing the set of test patterns to determine amount of coverage of the parameter space; obtaining characteristics of a set of test structures corresponding to the set of test patterns printed on a wafer using the lithography process at each of a set of process conditions, the set of process conditions being a subset of all possible process conditions within the process window; simulating, using the computer, the lithography process at each of the set of process conditions using a set of parameters corresponding to the model of the lithography process to produce simulated results, the set of parameters including the model parameters and a set of fitting parameters having variable values; determining values of the fitting parameters that produce simulated results that are a best fit with the characteristics of the set of test structures at all of the set of process conditions; and defining the model having the values of the fitting parameters. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21)
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Specification