Non-destructive acoustic metrology for void detection
First Claim
1. A method of non-destructive acoustic metrology for void detection in a via in a sample, the method comprising:
- generating a model for determining the existence of a void within the via, comprising;
generating a model signal representative of a signal that would be received from performing acoustic metrology on the via;
removing a signal component due to temperature rise and subsequent heat dissipation from the model signal;
generating a model periodogram by performing a Fourier transform over a sliding window;
applying a modified image processing segmentation algorithm to locate centroid locations of echo patterns in the model periodogram; and
generating a correlation of the centroid locations to a depth of where a model acoustic pulse was reflected within the via; and
directing an excitation laser beam at the via, such that an acoustic wave propagates through the via;
directing a probe laser beam at the via, such that the probe laser beam reflects off the sample, creating a reflected beam encoding data about propagation of the acoustic wave in the via;
analyzing the reflected beam, using a detection periodogram, to determine one or more detection centroids;
applying the generated correlation to determine the depth of an acoustic wave reflection associated with the one or more detection centroids;
comparing the determined depth with an expected depth for the via; and
based on the comparison of the determined depth with the expected depth, generating an indication that there is the void in the via.
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Accused Products
Abstract
Advanced interconnect technologies such as Through Silicon Vias (TSVs) have become an integral part of 3-D integration. Methods and systems and provided for laser-based acoustic techniques in which a short laser pulse generates broadband acoustic waves that propagate in the TSV structure. An optical interferometer detects the surface displacement caused by the acoustic waves reflecting within the structure as well as other acoustic waves traveling near the surface that has information about the structure dimensions and irregularities, such as voids. Features of voids, such as their location, are also identified based on the characteristics of the acoustic wave as it propagates through the via. Measurements typically take few seconds per site and can be easily adopted for in-line process monitoring.
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Citations
23 Claims
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1. A method of non-destructive acoustic metrology for void detection in a via in a sample, the method comprising:
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generating a model for determining the existence of a void within the via, comprising; generating a model signal representative of a signal that would be received from performing acoustic metrology on the via; removing a signal component due to temperature rise and subsequent heat dissipation from the model signal; generating a model periodogram by performing a Fourier transform over a sliding window; applying a modified image processing segmentation algorithm to locate centroid locations of echo patterns in the model periodogram; and generating a correlation of the centroid locations to a depth of where a model acoustic pulse was reflected within the via; and directing an excitation laser beam at the via, such that an acoustic wave propagates through the via; directing a probe laser beam at the via, such that the probe laser beam reflects off the sample, creating a reflected beam encoding data about propagation of the acoustic wave in the via; analyzing the reflected beam, using a detection periodogram, to determine one or more detection centroids; applying the generated correlation to determine the depth of an acoustic wave reflection associated with the one or more detection centroids; comparing the determined depth with an expected depth for the via; and based on the comparison of the determined depth with the expected depth, generating an indication that there is the void in the via. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of non-destructive acoustic metrology for void detection in a via in a sample, the method comprising:
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directing an excitation laser beam at the via, such that an acoustic wave propagates through the via; directing a probe laser beam at the via, such that the probe laser beam reflects off the sample, creating a reflected beam encoding data about propagation of the acoustic wave in the via; analyzing the reflected beam, using a periodogram, to identify a first centroid and a second centroid, wherein the first centroid has a first associated delay time and a first associated frequency and the second centroid has a second associated delay time and a second associated frequency; comparing the first and second associated delay times to an expected delay time for an ideally filled via; comparing the first and second associated frequencies to an expected frequency range; based on the comparison of the first and second delay times and the comparison of the first and second associated frequencies, generating an indication that the via contains one or more of the group selected from;
a void in a body of the via, a void at the bottom of the via, and no voids. - View Dependent Claims (14, 15, 16, 17)
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18. A system for non-destructive acoustic metrology for void detection in a via in a sample, the system comprising:
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a first source for generating a excitation beam directed towards the via in the sample; a second source for generating a probe beam directed towards the via in the sample; an optical sensor for detecting a reflected probe beam reflected from the sample; at least one processor; and a memory storing instructions, that when executed by the at least one processor, perform actions comprising; generate a model for determining the existence of a void within the via, comprising; generate a model signal representative of a signal that would be received from performing acoustic metrology on the via; remove a signal component due to temperature rise and subsequent heat dissipation from the model signal; generate a model periodogram by performing a Fourier transform over a sliding window; apply a modified image processing segmentation algorithm to locate centroid locations of echo patterns in the model periodogram; and generate a correlation of the centroid locations to a depth of where a model acoustic pulse was reflected within the via; and analyze data associated with the reflected beam, using a detection periodogram, to determine one or more detection centroids; compare features of the one or more detection centroids to expected features of the via to determine if there is a void in the via; and if there is the void in the via, generating an indication that there is the void in the via. - View Dependent Claims (19, 20, 21, 22)
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23. A substantially void-free integrated circuit device prepared by a process comprising the steps of:
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manufacturing at least a portion of a first wafer using one or more process tools; receiving the first wafer for inspection, wherein the first wafer includes multiple vias; directing an excitation laser beam at a via of the multiple vias, such that an acoustic wave propagates through the via; directing a probe laser beam at the via, such that the probe laser beam reflects off the sample, creating a reflected beam encoding data about propagation of the acoustic wave in the via; analyzing, using a periodogram, the reflected beam to identify a first centroid and a second centroid, wherein the first centroid has a first associated delay time and a first associated frequency and the second centroid has a second associated delay time and a second associated frequency; comparing the first and second associated delay times to an expected delay time for an ideally filled via; comparing the first and second associated frequencies to an expected frequency range; based on the comparison of the first and second delay times and the comparison of the first and second associated frequencies, determining that the wafer contains at least one void in one or more of the multiple vias; diverting the first wafer from production for additional inspection; modifying the operation of the one or more process tools to produce subsequent wafers that have a lower likelihood of having voids; and manufacturing a second wafer using the modified operation of the one or more process tools to produce the substantially void-free integrated circuit device.
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Specification