# US 2019/0355601 A1 · Phase filter for enhanced defect detection in multilayer structure > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0355601 A1 - Document ID: US20190355601A1 - Status: Published application - Kind: A1 - Application number: 16/100,818 - Filed: 2018-08-10 - Published: 2019-11-21 - Earliest claimed: 2018-05-18 - Assignees: KLA-Tencor Corporation - Applicants: KLA-Tencor Corporation - Inventors: Robert M. Danen; Dmitri G. Starodub - Web page: https://patentgrep.com/patent/US20190355601A1 ## CPC - G01N 21/95623: {using a spatial filtering method (per se G02B)} - H10P 72/0616: {Monitoring of warpages, curvatures, damages, defects or the like} - G01N 21/8806: {Specially adapted optical and illumination features} - G01N 21/95: characterised by the material or shape of the object to be examined (G01N21/89 - G01N21/91, G01N21/94 take precedence) - G01N 21/9505: {Wafer internal defects, e.g. microcracks} - G02B 27/0012: {Optical design, e.g. procedures, algorithms, optimisation routines} - G06F 30/23: using finite element methods [FEM] or finite difference methods [FDM] - H10P 74/203: {Structural properties, e.g. testing or measuring thicknesses, line widths, warpage, bond strengths or physical defects} - G01N 2021/8883: {involving the calculation of gauges, generating models} - G01N 2201/0675: SLM - G06F 2111/10: Numerical modelling - H10B 41/27: the channels comprising vertical portions, e.g. U-shaped channels - H10B 43/27: the channels comprising vertical portions, e.g. U-shaped channels - H10P 14/27: {using selective deposition, e.g. simultaneous growth of monocrystalline and non-monocrystalline semiconductor materials} - H10P 14/3411: {Silicon, silicon germanium or germanium} - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10 - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) - H10B: ELECTRONIC MEMORY DEVICES ## Abstract Disclosed are methods and apparatus for facilitating defect detection in a multilayer stack. The method includes selection of a set of structure parameters for modeling a particular multilayer stack and a particular defect contained within such particular multilayer stack and a set of operating parameters for an optical inspection system. Based on the set of structure and operating parameters, an electromagnetic simulation is performed of waves scattered from the particular multilayer stack and defect and arriving at a collection pupil of the optical inspection system. Based on the simulated waves at the collection pupil, a design of a phase filter having a plurality of positions for changing a plurality of phases within a plurality of corresponding positions of the collection pupil of the optical inspection tool is determined so as to compensate for an adverse effect of the particular multilayer stack on obtaining a defect signal for the defect within such particular multilayer stack and/or to enhance such defect signal. The design of the phase filter is then provided for fabrication or configuration of a phase filter inserted within the optical inspection system for detection of defects in multilayer stacks with the same structure parameters as the particular multilayer stack. Methods and systems for inspecting a multilayer stack for defects are also disclosed. ## Claims ### Claim 1 A method of facilitating defect detection in a multilayer stack, comprising: selecting a set of structure parameters for modeling a particular multilayer stack and a particular defect contained within such particular multilayer stack and a set of operating parameters for an optical inspection system; based on the set of structure and operating parameters, performing an electromagnetic simulation of waves scattered from the particular multilayer stack and defect and arriving at a collection pupil of the optical inspection system; based on the simulated waves at the collection pupil, determining a design of a phase filter having a plurality of positions for changing a plurality of phases at a plurality of corresponding positions within the collection pupil of the optical inspection tool so as to compensate for an adverse effect of the particular multilayer stack on obtaining a defect signal for the defect within such particular multilayer stack and/or to enhance such defect signal; and providing the design of the phase filter for fabrication or configuration of a phase filter inserted within the optical inspection system for detection of defects in multilayer stacks with the same structure parameters as the particular multilayer stack. ### Claim 2 (depends on 1) The method of claim 1, wherein the electromagnetic simulation is performed using a Rigorous Couple Wave Analysis (RCWA) technique, a Finite Difference Time Domain (FDTD) technique, or a Finite Element Method (FEM) technique. ### Claim 3 (depends on 1) The method of claim 1, wherein the structure parameters include one or more of the following multilayer stack parameters for each layer: thickness, shape, patterns, refractive index, line edge roughness (LER), or relative placement with respect to other layers, the structure parameters include one or more of the following defect parameters: defect position with respect to the multilayer stack, defect type, defect composition, defect size, or defect shape, and the operating parameters include one or more of the following parameters: one or more illumination polarizations, one or more scattered waves polarizations, one or more spectral bands, one or more incident angles, one or more collection angles, one or more optical attenuation filters, one or more focus settings, or one or more light exposure settings. ### Claim 4 (depends on 1) The method of claim 1, wherein: performing the electromagnetic simulation of waves scattered from the particular multilayer stack and defect comprises simulating a plurality of phase values at the collection pupil, via simulation of a scattering matrix, for the particular multilayer stack being both present and absent, and the design of the phase filter is based on a difference between the simulated phase values for the particular multilayer stack being present and the simulated phase values for the particular multilayer stack being absent. ### Claim 5 (depends on 4) The method of claim 4, wherein simulating the phase values includes averaging simulated phase values across a plurality of different incident angles, different collection angles, and different combinations of illumination polarizations and collection polarizations. ### Claim 6 (depends on 4) The method of claim 4, wherein determining a design of the phase filter further comprises interpolating the phase values on a finer grid than the grid used for simulating such phase values. ### Claim 7 (depends on 1) The method of claim 1, wherein determining a design of the phase filter further comprises combining such design with a focus shifting filter so as to minimize large changes in phase values across such phase filter. ### Claim 8 (depends on 1) The method of claim 1, wherein: performing an electromagnetic simulation of waves scattered from the particular multilayer stack and defect comprises performing an optimization process for applying a simulated phase filter, which has a plurality of positions for changing phase values, at the collection pupil to simulated scattered waves in order to find an optimized simulated phase filter, and the design of the phase filter is based on the optimized simulated phase filter. ### Claim 9 (depends on 8) The method of claim 8, wherein the optimization process includes maximizing a difference between a simulated image, at an image plane, of the particular multilayer stack with and without the particular defect. ### Claim 10 (depends on 8) The method of claim 8, wherein the optimization process includes minimizing deviation from an optimum system response in three dimensions, constrained by a wave propagation equation. ### Claim 11 (depends on 1) The method of claim 1, wherein the particular multilayer stack is a 3D NAND, FinFET, or DRAM structure on a semiconductor wafer. ### Claim 12 A method of inspecting a multilayer stack in an optical inspection tool, comprising: in the inspection tool, providing a phase filter having a plurality of positions for changing a plurality of phases at a plurality of positions of a collection pupil of the inspection tool, wherein the phase filter was designed to compensate for an adverse effect of a particular multilayer stack on obtaining a defect signal for a defect, if any, within such particular multilayer stack and/or to enhance such defect signal; generating an image based on light scattered from the particular multilayer stack in response to an incident beam directed towards such particular multilayer stack; and determining whether the particular multilayer stack has a defect based on the image. ### Claim 13 (depends on 12) The method of claim 12, further comprising determining a depth of such defect, if present, based on the image or a plurality of images generated at a plurality of depths of the particular multilayer stack. ### Claim 14 (depends on 12) The method of claim 12, wherein the phase filter was designed by: selecting a set of structure parameters for modeling the particular multilayer stack and a particular defect contained within such particular multilayer stack and a set of operating parameters for the optical inspection system; based on the set of structure and operating parameters, performing an electromagnetic simulation of waves scattered from the particular multilayer stack and defect and arriving at a collection pupil of the optical inspection system; and based on the simulated waves at the collection pupil, determining a design of the phase filter having a plurality of positions for changing a plurality of phases at a plurality of corresponding positions of the collection pupil of the optical inspection tool so as to compensate for an adverse effect of the particular multilayer stack on obtaining a defect signal for the defect within such particular multilayer stack and/or to enhance such defect signal. ### Claim 15 (depends on 12) The method of claim 12, wherein the phase filter has a fixed design. ### Claim 16 (depends on 12) The method of claim 12, wherein the phase filter is an adjustable phase/amplitude spatial light modulator, and the method further comprises adjusting the phase filter to optimize the defect signal in an image. ### Claim 17 An inspection system for detecting defects in a multilayer stack, the system comprising: a light source for generating an illumination beam; an illumination lens system for directing the illumination beam towards a multilayer stack; a collection lens system for directing towards a detector scattered light from a multilayer stack in response to the illumination beam, wherein the collection lens system includes a phase filter having a plurality of positions for changing a plurality of phases at a plurality of positions within a collection pupil of the system, wherein the phase filter was designed to compensate for an adverse effect of a particular multilayer stack on obtaining a defect signal for a defect, if any, within such particular multilayer stack and/or to enhance such defect signal; the detector for receiving the scattered light from a multilayer stack; and a controller operable to perform the following operations: generating an image based on light scattered from the particular multilayer stack in response to an incident beam directed towards the particular multilayer stack; and determining whether the particular multilayer stack has a defect based on the image. ### Claim 18 (depends on 17) The system of claim 17, wherein the phase filter was designed by: selecting a set of structure parameters for modeling the particular multilayer stack and a particular defect contained within such particular multilayer stack and a set of operating parameters for the inspection system; based on the set of structure and operating parameters, performing an electromagnetic simulation of waves scattered from the particular multilayer stack and defect and arriving at a collection pupil of the inspection system; and based on the simulated waves at the collection pupil, determining a design of the phase filter having a plurality of positions for changing a plurality of phases at a plurality of corresponding positions of the collection pupil of the inspection tool so as to compensate for an adverse effect of the particular multilayer stack on obtaining a defect signal for the defect within such particular multilayer stack and/or to enhance such defect signal. ### Claim 19 (depends on 17) The system of claim 17, wherein the phase filter has a fixed design. ### Claim 20 (depends on 17) The system of claim 17, wherein the phase filter is an adjustable phase/amplitude spatial light modulator, wherein the controller is further operable to adjust the phase filter to optimize the defect signal in an image.