Resolution improvement of acoustic microimaging by continuous wavelet transform for semiconductor inspection

Acoustic microimaging (AMI) is used as an important non-destructive tool in semiconductor reliability evaluation and failure analysis. As advanced microelectronic packages are being produced smaller and thinner, detection of the internal features and defects in the packages is approaching the resolution limits for conventional AMI. To meet this challenge, an acoustic time–frequency domain imaging technique is proposed in this paper, which utilizes the excellent time–frequency localization characteristics of the continuous wavelet transform (CWT) to improve the axial resolution of AMI, without increasing acoustic frequencies.The proposed technique is compared to time domain AMI, frequency domain AMI and sparse signal representation based AMI (SSRAMI) with respect to both axial resolution and robustness. Simulation results show that the proposed technique has superior performance compared to time domain and frequency domain AMI techniques, and has close performance to SSRAMI but with less computation load.