Apparatus and methods for detecting overlay errors using scatterometry
First Claim
1. A method for determining overlay between a plurality of first structures in a first layer of a sample and a plurality of second structures in a second layer of the sample, the method comprising:
- providing a plurality of targets that each include a portion of the first and second structures and each is designed to have an offset between its first and second structure portions;
illuminating the targets with electromagnetic radiation to obtain spectra for each target, wherein obtaining the spectra comprises acquiring radiation from the targets at a selected one or more wavelengths using an imaging system with wavelength selection and acquiring an image from each of the targets, wherein the spectra are an averaged or summed one or more intensity value(s) of one or more pixels of the corresponding target image;
selecting a wavelength using the imaging system such that contrast between the spectra is maximized; and
determining any overlay error between the first structures and the second structures using a scatterometry technique based on the obtained spectra for each target.
1 Assignment
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Accused Products
Abstract
Disclosed are techniques, apparatus, and targets for determining overlay error between two layers of a sample. Target A is designed to have an offset Xa between its first and second structures portions; target B is designed to have an offset Xb; target C is designed to have an offset Xc; and target D is designed to have an offset Xd. Each of the offsets Xa, Xb, Xc and Xd is preferably different from zero; Xa is an opposite sign and differ from Xb; and Xc is an opposite sign and differs from Xd. The targets A, B, C and D are illuminated with electromagnetic radiation to obtain spectra SA, SB, SC, and SD from targets A, B, C, and D, respectively. Any overlay error between the first structures and the second structures is then determined using a linear approximation based on the obtained spectra SA, SB, SC, and SD.
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Citations
45 Claims
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1. A method for determining overlay between a plurality of first structures in a first layer of a sample and a plurality of second structures in a second layer of the sample, the method comprising:
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providing a plurality of targets that each include a portion of the first and second structures and each is designed to have an offset between its first and second structure portions; illuminating the targets with electromagnetic radiation to obtain spectra for each target, wherein obtaining the spectra comprises acquiring radiation from the targets at a selected one or more wavelengths using an imaging system with wavelength selection and acquiring an image from each of the targets, wherein the spectra are an averaged or summed one or more intensity value(s) of one or more pixels of the corresponding target image; selecting a wavelength using the imaging system such that contrast between the spectra is maximized; and determining any overlay error between the first structures and the second structures using a scatterometry technique based on the obtained spectra for each target. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A method for determining overlay between a plurality of first structures in a first layer of a sample and a plurality of second structures in a second layer of the sample, the method comprising:
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providing targets A, B, C and D that each include a portion of the first and second structures, wherein the target A is designed to have an offset Xa between its first and second structures portions, wherein the target B is designed to have an offset Xb between its first and second structures portions, wherein the target C is designed to have an offset Xc between its first and second structures portions, wherein the target D is designed to have an offset Xd between its first and second structures portions, wherein each of the offsets Xa, Xb, Xc and Xd is different from zero, Xa is an opposite sign and differ from Xb, and Xc is an opposite sign and differs from Xd; illuminating the targets A, B, C and D with electromagnetic radiation to obtain spectra SA, SB, SC, and SD from targets A, B, C, and D, respectively; and determining any overlay error between the first structures and the second structures using a linear approximation based on the obtained spectra SA, SB, SC, and SD, wherein obtaining the spectra SA, SB, SC, and SD comprises acquiring radiation from the targets A, B, C, and D at a selected one or more wavelengths using an imaging system with wavelength selection, wherein obtaining the spectra SA, SB, SC, and SD comprises acquiring an image from the targets A, B, C, and D and wherein the spectra SA, SB, SC, and SD are an averaged or summed one or more intensity value(s) of one or more pixels of the corresponding target image, the method further comprising selecting a wavelength using the imaging system such that contrast between the SA, SB, SC, and SD is maximized. - View Dependent Claims (23)
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24. A system for determining overlay between a plurality of first structures in a first layer of a sample and a plurality of second structures in a second layer of the sample, comprising:
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a scatterometry module for illuminating a plurality of targets, which each include a portion of the first and second structures and each is designed to have an offset between its first and second structure portions, with electromagnetic radiation to obtain spectra from the targets, wherein the scatterometry module includes wavelength selection; and a processor operable for; with the scatterometry module, illuminating the targets with electromagnetic radiation to obtain spectra for each target, wherein obtaining the spectra comprises acquiring radiation from the targets at a selected one or more wavelengths so as to acquire an image from each of the targets, wherein the spectra are an averaged or summed one or more intensity value(s) of one or more pixels of the corresponding target image, selecting a wavelength using the wavelength selection of the scatterometry module such that contrast between the spectra is maximized, and determining any overlay error between the first structures and the second structures using a scatterometry technique based on the obtained spectra each target. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43)
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44. An imaging system for determining overlay between a plurality of first structures in a first layer of a sample and a plurality of second structures in a second layer of the sample, comprising:
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a scatterometry module for illuminating the targets A, B, C and D with electromagnetic radiation to obtain spectra SA, SB, SC, and SD from targets A, B, C, and D, respectively; and a processor operable for determining any overlay error between the first structures and the second structures using a linear approximation based on the obtained spectra SA, SB, SC, and SD, wherein targets A, B, C and D each include a portion of the first and second structures, wherein the target A is designed to have an offset Xa between its first and second structures portions, wherein the target B is designed to have an offset Xb between its first and second structures portions, wherein the target C is designed to have an offset Xc between its first and second structures portions, wherein the target D is designed to have an offset Xd between its first and second structures portions, and wherein each of the offsets Xa, Xb, Xc and Xd is different from zero, Xa is an opposite sign and differ from Xb, and Xc is an opposite sign and differs from Xd, wherein obtaining the spectra SA, SB, SC, and SD comprises acquiring radiation from the targets A, B, C, and D at a selected one or more wavelengths, wherein obtaining the spectra SA, SB, SC, and SD comprises acquiring an image from the targets A, B, C, and D and wherein the spectra SA, SB, SC, and SD are an averaged or summed one or more intensity value(s) of one or more pixels of the corresponding target image, the method further comprising selecting a wavelength using the imaging system such that contrast between the SA, SB, SC, and SD is maximized. - View Dependent Claims (45)
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Specification