Three-dimensional mask model for photolithography simulation
First Claim
1. A method implemented by a computer for creating a three-dimensional mask model, the method comprising:
- identifying features to include in a mask for which the three-dimensional mask model is to be created;
simulating the effect of light passing through the mask having the identified features using three-dimensional mask topography information to produce a theoretical image;
determining initial filtering kernels for the three-dimensional mask model using the theoretical image; and
modifying the initial filtering kernels until a total difference between the theoretical image and a simulated image is minimized or below a threshold to produce final filtering kernels,wherein the final filtering kernels are configured to be convolved with one or more mask transmission functions to produce a near-field image, and wherein the simulating, determining and modifying steps are implemented using the computer.
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Abstract
A three-dimensional mask model of the invention provides a more realistic approximation of the three-dimensional effects of a photolithography mask with sub-wavelength features than a thin-mask model. In one embodiment, the three-dimensional mask model includes a set of filtering kernels in the spatial domain that are configured to be convolved with thin-mask transmission functions to produce a near-field image. In another embodiment, the three-dimensional mask model includes a set of correction factors in the frequency domain that are configured to be multiplied by the Fourier transform of thin-mask transmission functions to produce a near-field image.
25 Citations
16 Claims
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1. A method implemented by a computer for creating a three-dimensional mask model, the method comprising:
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identifying features to include in a mask for which the three-dimensional mask model is to be created; simulating the effect of light passing through the mask having the identified features using three-dimensional mask topography information to produce a theoretical image; determining initial filtering kernels for the three-dimensional mask model using the theoretical image; and modifying the initial filtering kernels until a total difference between the theoretical image and a simulated image is minimized or below a threshold to produce final filtering kernels, wherein the final filtering kernels are configured to be convolved with one or more mask transmission functions to produce a near-field image, and wherein the simulating, determining and modifying steps are implemented using the computer. - View Dependent Claims (2, 3, 4, 5)
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6. A method implemented by a computer for creating a three-dimensional mask model, the method comprising:
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identifying features to include in a mask for which the three-dimensional mask model is to be created; simulating the effect of light passing through the mask having the identified features using three-dimensional mask topography information to produce a theoretical image; determining initial correction factors for the three-dimensional mask model using the theoretical image; and modifying the initial correction factors until a total difference between the theoretical image and a simulated image is minimized to produce final correction factors, wherein the final correction factors are configured to be multiplied by a Fourier transform of one or more mask transmission functions to produce a near-field image, and wherein the simulating, determining and modifying steps are implemented using the computer. - View Dependent Claims (7, 8)
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9. A photolithography simulation system implemented by a computer, the system comprising:
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a three-dimensional mask model of a type of photolithography mask, the three-dimensional mask model comprising one or more of; a correction factor configured to modify a mathematical transform of a mask transmission function of a mask; a correction factor configured to modify a mathematical transform of a first mask-edge function corresponding to a first angle of orientation associated with the mask; a correction factor configured to modify a mathematical transform of a second mask-edge function corresponding to a second angle of orientation associated with the mask; and a correction factor configured to modify a mathematical transform of a mask-corner function of the mask, wherein the correction factors represent one or more effects of the topography of the type of photolithography mask on light passing through a mask of that type; and a software tool executed by the computer using the three-dimensional mask model to simulate a near-field image expected to be produced by a photolithographic tool using the type of photolithography mask. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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Specification