Opto-acoustic metrology of signal attenuating structures

A method of manufacturing an interconnect structure for an integrated circuit (IC) device, the method comprising:

• forming the interconnect structure in the IC device;
• receiving a time-dependent opto-acoustic signal for the interconnect structure;
• performing a Fourier analysis of the time-dependent opto-acoustic signal to generate a Fourier-transformed dataset;
• identifying a plurality of local maxima from the Fourier-transformed dataset;
• generating an estimate of one or more optical parameters for each identified local maximum in the plurality of local maxima;
• fitting a first mode to a strongest maximum of the plurality of local maxima;
• subtracting the first mode from the time-dependent opto-acoustic signal to generate a first corrected dataset;
• fitting a second mode to a second strongest maximum of the plurality of local maxima;
• subtracting the second mode from the first corrected dataset to generate a second dataset;
• comparing the first and second datasets to a predicted physical model;
• based on the comparison, quantifying one or more physical characteristics of the interconnect structure of the integrated circuit;
• determining whether the one or more physical characteristics are within tolerances for the interconnect structure;
• and
• if the one or more physical characteristics are not within the tolerances, altering a fabrication process.