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 each of 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, measuring a plurality of optical signals at a plurality of incident angles, wherein there are predefined offsets between the first and second structures; and
determining and storing, in memory, an overlay error between the first and second structures by analyzing the measured optical signals at the plurality of incident angles from the periodic targets using a scatterometry overlay technique based on the predefined offsets without using a calibration operation or a model-based regression technique,wherein the scatterometry overlay technique is a phase based technique that includes representing each of the first and second 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.
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Abstract
Disclosed is a method of determining an overlay error between two layers of a multiple layer sample. For each of a plurality of periodic targets target that each have a first structure formed from a first layer and a second structure formed from a second layer of the sample, a plurality of optical signals are measured at a plurality of incident angles, wherein there are predefined offsets between the first and second structures. An overlay error is then determined between the first and second structures by analyzing the measured optical signals at the plurality of incident angles from the periodic targets using a scatterometry overlay technique based on the predefined offsets without using a calibration operation.
149 Citations
11 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 each of 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, measuring a plurality of optical signals at a plurality of incident angles, wherein there are predefined offsets between the first and second structures; and determining and storing, in memory, an overlay error between the first and second structures by analyzing the measured optical signals at the plurality of incident angles from the periodic targets using a scatterometry overlay technique based on the predefined offsets without using a calibration operation or a model-based regression technique, wherein the scatterometry overlay technique is a phase based technique that includes representing each of the first and second 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of determining an overlay error between two layers of a multiple layer sample, the method comprising:
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for each of a plurality of periodic targets target that each have a first structure formed from a first layer and a second structure formed from a second layer of the sample, measuring a plurality of optical signals at a plurality of incident angles, wherein there are predefined offsets between the first and second structures; determining and storing, in memory, an overlay error between the first and second structures by analyzing the measured optical signals at the plurality of incident angles from the periodic targets using a scatterometry overlay technique based on the predefined offsets without using a calibration operation or a model-based regression technique, wherein each first structure has a first center of symmetry and each second structure has a second center of symmetry and wherein the first center of symmetry and the second center of symmetry for each target are offset with respect to each other by a selected one of the predefined offsets; and comparing the measured optical signals to theoretical data, using a model-based regression technique, to thereby determine and store, in memory, a second overlay error between the first and second structures. - View Dependent Claims (11)
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Specification