Nondestructive inspection of metallic microstructure chips based on photoacoustic remote sensing microscopy

Nondestructive testing of packaged chips is essential for ensuring product performance, yet existing methods have serious drawbacks. Here, we apply photoacoustic remote sensing microscopy using a high-frequency pulse laser with a pulse width of 1.2 ps and a wavelength of 1030 nm to inspect silicon-based semiconductor chips for internal defects. Joint optical-mechanical scanning allowed high-resolution imaging of a large field of view. The basis for photoacoustic imaging was explained using a solid-state physics model, which was confirmed experimentally by measuring photoacoustic amplitudes at different doping concentrations. Our method appears capable of rapidly imaging chips over a large field of view with depth-to-resolution ratios of around 200 without the need for a couplant, which could support nondestructive inspection in industrial applications.