Method for lithography model calibration
First Claim
1. A method for lithography model calibration, comprising:
- selecting a model for a lithography process, the model including an optical model and a resist model, the optical model having initial values of optical model parameters and the resist model having initial values of resist model parameters;
measuring an aerial image using an image sensor array to produce a measured sensor image, the aerial image being produced by a lithography tool from a mask created using circuit design data;
simulating the lithography process using the optical model and the circuit design data to produce a simulated aerial image;
determining differences between the simulated aerial image and the measured sensor image; and
modifying the values of the optical model parameters based on the differences between the simulated aerial image and the measured sensor image to identify optimal values for the optical model parameters, wherein a simulated aerial image produced using the optimal values for the optical model parameters is an optimal simulated aerial image that is a best match for the measured sensor image.
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Accused Products
Abstract
A method for separately calibrating an optical model and a resist model of lithography process using information derived from in-situ aerial image measurements to improve the calibration of both the optical model and the resist model components of the lithography simulation model. Aerial images produced by an exposure tool are measured using an image sensor array loaded into the exposure tool. Multiple embodiments of measuring aerial image information and using the measured aerial image information to calibrate the optical model and the resist model are disclosed. The method of the invention creates more accurate and separable optical and resist models, leading to better predictability of the pattern transfer process from mask to wafer, more accurate verification of circuit patterns and how they will actually print in production, and more accurate model-based process control in the wafer fabrication facility.
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Citations
104 Claims
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1. A method for lithography model calibration, comprising:
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selecting a model for a lithography process, the model including an optical model and a resist model, the optical model having initial values of optical model parameters and the resist model having initial values of resist model parameters; measuring an aerial image using an image sensor array to produce a measured sensor image, the aerial image being produced by a lithography tool from a mask created using circuit design data; simulating the lithography process using the optical model and the circuit design data to produce a simulated aerial image; determining differences between the simulated aerial image and the measured sensor image; and modifying the values of the optical model parameters based on the differences between the simulated aerial image and the measured sensor image to identify optimal values for the optical model parameters, wherein a simulated aerial image produced using the optimal values for the optical model parameters is an optimal simulated aerial image that is a best match for the measured sensor image. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method for calibrating a model of a lithography process, comprising:
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selecting a model for a lithography process, the model including an optical model and a resist model, the optical model having initial values of optical model parameters; selecting a sensor model for an image sensor array, the sensor model having initial values of sensor model parameters; measuring an aerial image using the image sensor array to produce a measured sensor image, the aerial image being produced by a lithography tool from a mask created using circuit design data; simulating behavior of the image sensor array using the optical model, the sensor model, and the circuit design data to produce a simulated sensor image; determining differences between the measured sensor image and the simulated sensor image; and modifying the optical model parameters and the sensor model parameters based on the differences between the measured sensor image and the simulated sensor image to identify optimal values for the optical model parameters and optimal values for the sensor model parameters, wherein a simulated sensor image produced using the optimal values for the optical model parameters and the optimal values for the sensor model parameters is an optimal simulated sensor image that is a best match for the measured sensor image. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34)
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35. A method for calibrating a model of a lithography process, comprising:
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selecting a model for a lithography process, the model including an optical model and a resist model, the optical model having initial values of optical model parameters; selecting a sensor model for an image sensor array, the sensor model having initial values of sensor model parameters; measuring an aerial image using the image sensor array to produce a measured sensor image, the aerial image being produced by a lithography tool from a mask created using circuit design data; simulating the lithography process using the optical model and the circuit design data to produce a simulated aerial image; simulating behavior of the image sensor array using the simulated aerial image and the sensor model to produce a simulated sensor image; determining differences between the measured sensor image and the simulated sensor image; and modifying the optical model parameters and the sensor model parameters based on the differences between the measured sensor image and the simulated sensor image to identify optimal values for the optical model parameters and optimal values for the sensor model parameters, wherein a simulated sensor image produced using the optimal values for the optical model parameters and the optimal values for the sensor model parameters is an optimal simulated sensor image that is a best match for the measured sensor image. - View Dependent Claims (36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54)
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55. A method for calibrating a model of a lithography process, comprising:
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selecting a model for a lithography process, the model including an optical model and a resist model, the optical model having initial values of optical model parameters and the resist model having initial values of resist model parameters; selecting an inverse sensor model for an image sensor array, the inverse sensor model having initial values of inverse sensor model parameters; measuring an aerial image using the image sensor array to produce a measured sensor image, the aerial image being produced by a lithography tool from a mask created using circuit design data; generating a reconstructed aerial image using the measured sensor image and the inverse sensor model; simulating the lithography process using the optical model and the circuit design data to produce a simulated aerial image; determining differences between the simulated aerial image and the reconstructed aerial image; and modifying the optical model parameters and the inverse sensor model parameters based on the differences between the simulated aerial image and the reconstructed aerial image to identify optimal values for the optical model parameters and optimal values for the inverse sensor model parameters, wherein a simulated aerial image produced using the optimal values for the optical model parameters is an optimal simulated aerial image that is a best match for the reconstructed aerial image. - View Dependent Claims (56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71)
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72. A method for calibrating a model of a lithography process, comprising:
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selecting a model for a lithography process, the model including an optical model and a resist model, the optical model having initial values of optical model parameters and the resist model having initial values of resist model parameters; selecting a sensor model for an image sensor array, the sensor model having values of sensor model parameters; measuring an aerial image using the image sensor array to produce a measured sensor image, the aerial image being produced by a lithography tool from a mask created using circuit design data; processing a wafer using the lithography process and the mask to produce printed resist patterns; measuring the printed resist patterns to produce measured resist patterns; simulating behavior of the image sensor array using the optical model, the circuit design data, and the sensor model to produce a simulated sensor image; determining differences between the measured sensor image and the simulated sensor image; simulating the lithography process using the optical model and the circuit design data to produce a simulated aerial image; simulating formation of resist patterns on a wafer using the resist model and the simulated aerial image to produce simulated resist patterns; determining differences between the simulated resist patterns and the measured resist patterns; and modifying the values of the optical model parameters and the resist model parameters based on a total difference between the simulated resist patterns and the measured resist patterns as well as between the measured sensor image and the simulated sensor image to identify optimal values for the optical model parameters and optimal values for the resist model parameters simultaneously, wherein simulated resist patterns produced using the optimal values for the resist model parameters are optimal simulated resist patterns that are a best match for the measured resist patterns, and wherein a simulated sensor image produced using the optimal values for the optical model parameters is an optimal simulated sensor image that is a best match for the measured sensor image. - View Dependent Claims (73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86)
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87. A computer-readable medium containing instructions for calibrating a model of a lithography process by performing:
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storing a model for a lithography process, the model including an optical model and a resist model, the optical model having initial values of optical model parameters, and the resist model having initial values of resist model parameters; storing a sensor model for an image sensor array, the sensor model having initial values of sensor model parameters; receiving a measured sensor image produced by measuring an aerial image using the image sensor array, the aerial image produced by a lithography tool from a mask created using circuit design data; simulating the lithography process using the optical model and the circuit design data to produce a simulated aerial image; simulating behavior of the image sensor array using the simulated aerial image and the sensor model to produce a simulated sensor image; determining differences between the simulated sensor image and the measured sensor image; and modifying the optical model parameters and the sensor model parameters based on the differences between the simulated sensor image and the measured sensor image to identify optimal values for the optical model parameters and optimal values for the sensor model parameters, wherein a simulated sensor image produced using the optimal values for the optical model parameters and the optimal values for the sensor model parameters is an optimal simulated sensor image that is a best match for the measured sensor image. - View Dependent Claims (88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104)
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Specification