Method and apparatus for determining an accurate photolithography process model
AssigneeSynopsys, Inc.
InventorsJensheng Huang, Chun-Chieh Kuo, Lawrence S. Melvin, III
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Abstract
One embodiment of the present invention provides a system that determines an accurate process model. During operation, the system receives process data. Next, the system receives an optical model which models an optical system of a photolithography process. The system then determines a stack model using the optical model, wherein the stack model models the effects of the photolithography process on the stack layers. Finally, the system determines a process model using the optical model, the stack model, and the process data.
Claims16
A method for determining a process model, the method comprising:
- receiving process data which is obtained by:
- subjecting one or more layouts to a photolithography process to create features on one or more wafers, and
- measuring dimensions of the features;
- receiving an optical model which models the photolithography process's optical system, wherein the optical model is a first weighted sum of a set of orthogonal functions;
- determining an uncalibrated stack model for modeling stack layers, wherein the uncalibrated stack model uses a subset of the set of orthogonal functions;
- based on Zernike polynomials
- determining an uncalibrated process model by combining the optical model and the uncalibrated stack model;
- and
- determining a calibrated process model by fitting the uncalibrated process model to the process data, wherein the calibrated process model is a second weighted sum of the set of orthogonal functions.
A computer-readable storage medium storing instructions that when executed by a computer cause the computer to perform a method for determining a process model, the method comprising:
- receiving process data which is obtained by:
- subjecting one or more layouts to a photolithography process to create features on one or more wafers, and
- measuring dimensions of the features;
- receiving an optical model which models the photolithography process's optical system, wherein the optical model is a first weighted sum of a set of orthogonal functions;
- based on Zernike polynomials
- determining an uncalibrated stack model for modeling stack layers, wherein the uncalibrated stack model uses a subset of the set of orthogonal functions;
- determining an uncalibrated process model by combining the optical model and the uncalibrated stack model;
- and
- determining a calibrated process model by fitting the uncalibrated process model to the process data, wherein the calibrated process model is a second weighted sum of the set of orthogonal functions.
A method for determining a process model, the method comprising:
- receiving an optical model which models an optical system of a photolithography process, wherein the optical model is represented using the expression ΣCiZi, where Ci is the ith optical coefficient and Zi, is the ith Zernike polynomial;
- receiving an uncalibrated stack model for modeling stack layers, wherein the uncalibrated stack model is represented using the expression ΣC′iZi, where C′i is the ith stack coefficient and Zi is the ith Zernike polynomial, wherein the set of Zernike polynomials used in the uncalibrated stack model is a subset of the set of Zernike polynomials used in the optical model;
- receiving process data which is obtained by:
- subjecting one or more layouts to a photolithography process to create features on one or more wafers, and
- measuring dimensions of the features;
- determining an uncalibrated process model by combining the optical model and the uncalibrated stack model;
- and
- determining a calibrated process model by fitting the uncalibrated process model to the process data.
A computer-readable storage medium storing instructions that when executed by a computer cause the computer to perform a method for determining a process model, the method comprising:
- receiving an optical model which models an optical system of a photolithography process, wherein the optical model is represented using the expression ΣCiZi, where Ci is the ith optical coefficient and Zi, is the ith Zernike polynomial;
- receiving an uncalibrated stack model for modeling stack layers, wherein the uncalibrated stack model is represented using the expression ΣC′iZi, where C′i is the ith stack coefficient and Zi, is the ith Zernike polynomial, wherein the set of Zernike polynomials used in the uncalibrated stack model is a subset of the set of Zernike polynomials used in the optical model;
- receiving process data which is obtained by:
- subjecting one or more layouts to a photolithography process to create features on one or more wafers, and
- measuring dimensions of the features;
- determining an uncalibrated process model by combining the optical model and the uncalibrated stack model;
- and
- determining a calibrated process model by fitting the uncalibrated process model to the process data.
Dependencies are inferred from the claim text.