Acoustic microscopy – a powerful tool to inspect microstructures of electronical devices

To increase the efficiency of electronic devices their structures are getting smaller and the layered constructions are getting more complex. The inspection of these small and thin structures gives new demands on the NDT, especially in lateral and depth resolution. High-end X-ray tomography is one inspection method, which allows detecting cracks or delaminations. However, it is time consuming. Ultrasonic techniques are able to detect cracks, delaminations, and other non homogeneities, too. Acoustic microscopy is the high-end application of ultrasonic techniques. Using frequencies between 3 MHz and 2000 MHz (2 GHz) it is possible to detect defects even in the sub micron-range. In combination with scanning units with a resolution of 0.1 μm, modified transducers and special software microstructures of layered electronic devices can be inspected very fast. This method will be presented at several examples of semiconductor devices. It will be shown, that in-line-inspection with acoustic microscopy is possible.