# US 2014/0195993 A1 · Three-dimensional mask model for photolithography simulation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0195993 A1 - Document ID: US20140195993A1 - Status: Published application - Kind: A1 - Application number: 14/081,386 - Filed: 2013-11-15 - Published: 2014-07-10 - Earliest claimed: 2013-01-08 - Assignees: ASML Netherlands B.V. - Applicants: Asml Netherlands B.V. - Inventors: Peng LIU; Yu Cao; Luoqi Chen; Jun Ye - Web page: https://patentgrep.com/patent/US20140195993A1 ## CPC - G06F 30/398: Design verification or optimisation, e.g. using design rule check [DRC], layout versus schematics [LVS] or finite element methods [FEM] (optical proximity correction [OPC] design processes G03F1/36) - G03F 1/36: Masks having proximity correction features; Preparation thereof, e.g. optical proximity correction [OPC] design processes - G03F 1/70: Adapting basic layout or design of masks to lithographic process requirements, e.g., second iteration correction of mask patterns for imaging - G03F 7/70441: {Optical proximity correction [OPC]} - G03F 7/705: {Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions} - G06F 30/20: Design optimisation, verification or simulation (optimisation, verification or simulation of circuit designs G06F30/30) - G06F 30/33: Design verification, e.g. functional simulation or model checking - G03F 1/50: Mask blanks not covered by G03F1/20 - G03F1/34; Preparation thereof - G03F 1/76: Patterning of masks by imaging - G06F 30/30: Circuit design - G06F 30/337: Design optimisation - G06F 30/39: Circuit design at the physical level (physical level design for reconfigurable circuits G06F30/347) - G06F 2111/10: Numerical modelling - G06F 2119/18: Manufacturability analysis or optimisation for manufacturability - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) - G03F: PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR; (phototypographic composing devices B41B; photosensitive materials or processes for photographic purposes G03C; electrophotography, sensitive layers or processes therefor G03G) ## 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. ## Claims ### Claim 1 A method implemented by a computer for creating a three-dimensional mask model, the method comprising: simulating the effect of light passing through a mask using three-dimensional mask topography information to produce a theoretical image; determining initial filtering kernels for a 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 predetermined 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. ### Claim 2 (depends on 1) The method of claim 1, wherein the mask transmission functions include one or more of a standard thin-mask transmission function and derivatives of the standard thin-mask transmission function. ### Claim 3 (depends on 1) The method of claim 1, wherein the final filtering kernels are independent of the layout of any particular mask if the mask has certain characteristics for which the three-dimensional mask model is created. ### Claim 4 (depends on 1) The method of claim 1, wherein the final filtering kernels include a linear filtering kernel and at least one bilinear filtering kernel. ### Claim 5 (depends on 1) The method of claim 1, wherein the three-dimensional mask topography information was produced by inspecting a manufactured calibration mask. ### Claim 6 (depends on 1) The method of claim 1, wherein simulating the effect of light passing through a mask includes simulating a plane wave of light and oblique waves of light passing through the mask. ### Claim 7 A method implemented by a computer for creating a three-dimensional mask model, the method comprising: simulating the effect of light passing through a mask using three-dimensional mask topography information to produce a theoretical image; determining initial correction factors for a 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. ### Claim 8 (depends on 7) The method of claim 7, wherein the final correction factors are independent of the layout of any particular mask if the mask has certain characteristics for which the three-dimensional mask model is created. ### Claim 9 (depends on 7) The method of claim 7, wherein the three-dimensional mask topography information was produced by inspecting a manufactured calibration mask. ### Claim 10 (depends on 7) The method of claim 7, wherein simulating the effect of light passing through a mask includes simulating a plane wave of light and oblique waves of light passing through the mask, and one or more of the final correction factors models oblique incidence effects.