Nonlinear beamforming for Scanning Acoustic Microscopy Imaging through scattering surfaces

Scanning Acoustic Microscopy (SAM) is a non-destructive evaluation technique that is widely used in the semiconductor and microelectronics industries. Image quality and defect detectability are typically degraded by scattering, either on the surface or during wave propagation within the sample. In this study, we combine the Synthetic Aperture Focusing Technique (SAFT) and nonlinear beamforming to minimize the effects of scattering. The method is characterized by using synthetic data and then compared to SAM imaging using linear beamforming. Finally, the technique is also demonstrated on a reference microelectronic sample. Both investigations demonstrate a significant improvement in imaging quality with fewer artifacts, higher Signal-to-noise ratio (SNR), and enhanced spatial resolution.