Contribution
Signal-based estimation of reconstruction parameters for Synthetic Aperture Focusing in Scanning Acoustic Microscopy
* Presenting author
Abstract:
Scanning Acoustic Microscopy (SAM) is a standard technique for failure analysis and quality assurance in microelectronics, detecting phenomena such as delamination at interfaces. The complexity of modern semiconductor devices has increased significantly in recent years. They consist of a large number of components of different sizes and materials. Consequently, comprehensive inspection of numerous interfaces at varying depths is essential. As SAM uses highly focused transducers with limited depth of field, the inspection time is dramatically increased as a separate scan is required for each depth.Synthetic Aperture Focusing Technique (SAFT) overcomes this problem via a reconstruction for the entire 3D-region of interest from multiple lateral measurement position of a single scan with fixed focus. The recently developed Near-field SAFT approach enhances the capabilities of SAFT on SAM data, but also presents additional challenges in the selection of appropriate reconstruction parameters, in particular the depth of focus and speed of sound.This contribution presents a new signal-based parameter estimation approach that operates directly on the signals without requiring detailed knowledge of the sample. The uncertainty of the reconstruction parameters and the quality of reconstruction are discussed. The comparison between signal-based and simulation-based parameter estimation provides a better understanding of Near-Field SAFT.