Apparatus and methods for detecting overlay errors using scatterometry
First Claim
1. A method of determining an overlay error between two layers of a multiple layer sample, the method comprising:
- for a plurality of periodic targets that each have a first structure formed from a first layer and a second structure formed from a second layer of the sample, employing an interferometer to modulate substantially a plurality of wavelengths of a broadband source and then acquiring one or more images of the periodic targets, wherein there are predefined offsets between the first and second structures; and
determining and storing an overlay error between the first and second structures by analyzing the one or more acquired images from the periodic targets using a scatterometry overlay technique based on the predefined offsets.
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Abstract
Disclosed is a method of determining an overlay error between two layers of a multiple layer sample. For a plurality of periodic targets that each have a first structure formed from a first layer and a second structure formed from a second layer of the sample, an interferometer is employed to modulate substantially a plurality of wavelengths of a broadband source and then acquiring one or more images of the periodic targets. There are predefined offsets between the first and second structures. An overlay error between the first and second structures is then determined by analyzing the one or more acquired images from the periodic targets using a scatterometry overlay technique based on the predefined offsets.
138 Citations
33 Claims
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1. A method of determining an overlay error between two layers of a multiple layer sample, the method comprising:
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for a plurality of periodic targets that each have a first structure formed from a first layer and a second structure formed from a second layer of the sample, employing an interferometer to modulate substantially a plurality of wavelengths of a broadband source and then acquiring one or more images of the periodic targets, wherein there are predefined offsets between the first and second structures; and determining and storing an overlay error between the first and second structures by analyzing the one or more acquired images from the periodic targets using a scatterometry overlay technique based on the predefined offsets. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of determining an overlay error between two layers of a multiple layer sample, the method comprising:
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for a plurality of theoretical overlay errors and a plurality of target configurations and/or process conditions, generating a plurality of theoretical scatterometry signals on the plurality of target configurations using a model or calibrated data; storing the plurality of theoretical scatterometry signals and their associated theoretical overlay errors and target configurations and/or process conditions; for each of a plurality of measured periodic targets that each have a first structure formed from a first layer and a second structure formed from a second layer of the sample, measuring an optical signal, wherein there are predefined offsets between the first and second structures; determining a measured overlay error between the first and second structures by analyzing the measured optical signals from the periodic targets using a scatterometry overlay technique based on the predefined offsets without using a calibration operation, wherein the scatterometry overlay technique is a phase based technique that includes representing each of the measured optical signals as a set of periodic functions having a plurality of known parameters and an unknown overlay error parameter and analyzing the set of periodic functions to solve for the unknown overlay error parameter to thereby determine the measured overlay error; and comparing the measured scatterometry signal with the stored theoretical scatterometry signals to obtain and store a characteristic of the measured periodic targets'"'"' configuration or process condition for such measured periodic targets based on a substantially matching theoretical overlay error and measured overlay error. - View Dependent Claims (15, 16)
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17. A method for determining an overlay error between at least two layers in a multiple layer sample, the method comprising:
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(a) using an optical system to measure a plurality of measured optical signals from a plurality of periodic targets on the sample, wherein the periodic targets each have a first structure in a first layer and a second structure in a second layer, wherein there are predefined offsets between the first and second structures, wherein the optical signals are measured at a same focus setting of the optical system without refocusing; (b) using a scatterometry overlay technique to analyze the measured optical signals of the periodic targets and the predefined offsets of the first and second structures of the periodic targets to thereby determine and store an overlay error between the first and second structures of the periodic targets; and for a second plurality of periodic targets, repeating operations (a) and (b) for a second focus setting wherein the optical signals are measured at the same second focus setting of the optical system without refocusing. - View Dependent Claims (18, 19, 20, 21, 22, 23)
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24. A method for determining an overlay error between at least two layers in a multiple layer sample, the method comprising:
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using an optical system to measure a plurality of measured optical signals from a plurality of periodic targets that each have a first structure formed from a first layer and a second structure formed from a second layer on the sample, wherein each first and second structure of each target are designed to have a predefined offset with respect to each other; using a scatterometry overlay technique to analyze the measured optical signals of the periodic targets and the predefined offsets of the first and second structures of the periodic targets to thereby determine and store a first overlay error between the first and second structures of the periodic targets; and using a model based technique to analyze the measured optical signals of the periodic targets to thereby determine a second overlay error between the first and second structures of the periodic targets, wherein the model based technique is based on the first overlay error. - View Dependent Claims (25, 26, 27, 28, 29)
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30. A method for aligning an imprint lithography mask with a semiconductor wafer, the method comprising:
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(a) aligning a plurality of periodic alignment marks of the mask with a plurality of alignment marks on the wafer; (b) using an optical system to measure a plurality of measured optical signals from a plurality of the periodic alignment marks on the mask and on the wafer, wherein the periodic alignment marks each have a first structure in a first layer and a second structure in a second layer, wherein there are predefined offsets between the first and second structures; (c) using a scatterometry overlay technique to analyze the measured optical signals of the periodic alignment marks and the predefined offsets of the first and second structures of the periodic alignment marks to thereby determine and store an overlay error or mask registration error between the mask and the wafer, wherein the scatterometry overlay technique is a phase based technique that includes representing each of the measured optical signals as a set of periodic functions having a plurality of known parameters and an unknown overlay error parameter and analyzing the set of periodic functions to solve for the unknown overlay error parameter to thereby determine the overlay error; and (d) repeating operations (a) through (c) until the overlay error or mask registration error equals a predetermined offset or is within a predetermined range of mask misregistration values. - View Dependent Claims (31, 32, 33)
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Specification