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 first optical signal using a first ellipsometer or a first reflectometer and a second optical signal using a second ellipsometer or a second reflectometer, 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 first and second 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 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 that each have a first structure formed from a first layer and a second structure formed from a second layer of the sample, a first optical signal is measured using a first ellipsometer or a first reflectometer and a second optical signal is measured using a second ellipsometer or a second reflectometer. 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 first and second optical signals from the periodic targets using a scatterometry overlay technique based on the predefined offsets.
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Citations
12 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 first optical signal using a first ellipsometer or a first reflectometer and a second optical signal using a second ellipsometer or a second reflectometer, 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 first and second 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 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, 10, 11, 12)
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Specification