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 optical system to thereby measure an optical signal from each 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 measured optical signals from the periodic targets using a scatterometry overlay technique based on the predefined offsets,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 a plurality of unknown parameters that include 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, wherein the number of targets equals the number of unknown parameters,wherein the optical system comprises any one or more of the following apparatus;
an imaging reflectometer, an imaging spectroscopic reflectometer, a polarized spectroscopic imaging reflectometer, a scanning reflectometer system, a system with two or more reflectometers capable of parallel data acquisition, a system with two or more spectroscopic reflectometers capable of parallel data acquisition, a system with two or more polarized spectroscopic reflectometers capable of parallel data acquisition, a system with two or more polarized spectroscopic reflectometers capable of serial data acquisition without moving the wafer stage or moving any optical elements or the reflectometer stage, imaging spectrometers, imaging system with wavelength filter, imaging system with long-pass wavelength filter, imaging system with short-pass wavelength filter, imaging system without wavelength filter, interferometric imaging system, imaging ellipsometer, a spectroscopic ellipsometer, a laser ellipsometer having a photoelastic modulator, an imaging spectroscopic ellipsometer, a scanning ellipsometer system, a system with two or more ellipsometers capable of parallel data acquisition, a system with two or more ellipsometers capable of serial data acquisition without moving the wafer stage or moving any optical elements or the ellipsometer stage, a Michelson interferometer, and a Mach-Zehnder interferometer, a Sagnac interferometer, a scanning angle of incidence system, a scanning azimuth angle system, a +/−
first order differential reflectometer, and/or a +/−
first order differential polarized reflectometer.
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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 optical system is employed to thereby measure an optical signal from each of the periodic targets. There are predefined offsets between the first and second structures. An overlay error is determined 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.
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Citations
44 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 optical system to thereby measure an optical signal from each 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 measured optical signals from the periodic targets using a scatterometry overlay technique based on the predefined offsets, 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 a plurality of unknown parameters that include 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, wherein the number of targets equals the number of unknown parameters, wherein the optical system comprises any one or more of the following apparatus;
an imaging reflectometer, an imaging spectroscopic reflectometer, a polarized spectroscopic imaging reflectometer, a scanning reflectometer system, a system with two or more reflectometers capable of parallel data acquisition, a system with two or more spectroscopic reflectometers capable of parallel data acquisition, a system with two or more polarized spectroscopic reflectometers capable of parallel data acquisition, a system with two or more polarized spectroscopic reflectometers capable of serial data acquisition without moving the wafer stage or moving any optical elements or the reflectometer stage, imaging spectrometers, imaging system with wavelength filter, imaging system with long-pass wavelength filter, imaging system with short-pass wavelength filter, imaging system without wavelength filter, interferometric imaging system, imaging ellipsometer, a spectroscopic ellipsometer, a laser ellipsometer having a photoelastic modulator, an imaging spectroscopic ellipsometer, a scanning ellipsometer system, a system with two or more ellipsometers capable of parallel data acquisition, a system with two or more ellipsometers capable of serial data acquisition without moving the wafer stage or moving any optical elements or the ellipsometer stage, a Michelson interferometer, and a Mach-Zehnder interferometer, a Sagnac interferometer, a scanning angle of incidence system, a scanning azimuth angle system, a +/−
first order differential reflectometer, and/or a +/−
first order differential polarized reflectometer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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34. 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 optical system to thereby measure an optical signal from each of the periodic targets, wherein there are predefined offsets between the first and second structures; and determining an 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, wherein the optical system is a polarized spectroscopic imaging reflectometer.
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35. A method for determining an overlay error between at least two layers in a multiple layer sample, the method comprising:
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providing a plurality of periodic targets that 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; adjusting a polarization modulator of an ellipsometer to a plurality of different polarization states; measuring a plurality of measured signals from the periodic targets for each different polarization state; and using a scatterometry overlay technique to analyze the measured 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, wherein, the scatterometry overlay technique is a phase based technique that includes representing each of the measured signals, that was measured for each different polarization state and periodic target, as a set of periodic functions having a plurality of known parameters and a plurality of unknown parameters that include 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, wherein the number of targets equals the number of unknown parameters. - View Dependent Claims (36, 37, 38, 39, 40, 41, 42, 43, 44)
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Specification