Session: Poster & Student Poster Session

Paper Number: 171313

171313 - A High-Frequency Passive Imaging Approach for Anisotropic Structures: Application to Silicon 

Abstract: 

Layer-on-substrate structures are often susceptible to various types of defects, particularly those introduced during the thin-film deposition process. While conventional inspection techniques rely on interdigital transducers (IDTs) for wave excitation and laser vibrometry for detection, this work presents a complementary passive imaging approach inspired by noise correlation methods initially developed in geophysics.

The method leverages the correlation of high-frequency diffuse acoustic fields to reconstruct the passive Green's function, enabling defect detection and imaging without active source scanning. The approach was evaluated through simulations and preliminary experiments conducted on 3 mm thick silicon wafers with locally deposited silver lacquer layers (~10 µm) acting as artificial impedance mismatches. These artificial defects were specifically introduced to simulate localized failures that could occur in the thin films during manufacturing.

Surface acoustic waves were generated using wideband IDTs operating in the 10–25 MHz range, and the resulting displacement fields were recorded using a laser vibrometer. Correlation matrices were constructed for both defective and defect-free cases and organized in a Full Matrix Capture (FMC) format. This matrix-based approach allows for a detailed analysis of the acoustic wave propagation and scattering within the structure. Defect localization was performed using a beamforming algorithm, incorporating prior knowledge of sensor positions and analytically estimated surface wave slowness curves.

Presenting Author: Lynda Chehami iemn

Presenting Author Biography: Associate Professor (HDR)
Member of CNU 63
President of the ULTRASOUNDS Technical Committee of the European Acoustics Association (EEA)
https://euracoustics.org/technical-committees/ultrasounds

Authors:

Nada Ben Jafela IEMN
Lynda Chehami iemn
Marc Duquennoy IEMN
Emmanuel Moulin IEMN