High-resolution interferometry and electronic speckle pattern interferometry applied to the thermomechanical study of a MOS power transistor

We present an original optical approach for the thermomechanical study of electronic devices. We have applied it to image the deformation undergone by a MOS power transistor due to its operation. This imaging method allows the derivation of the three components of. the displacement vector of each point of the surface of the component while heated by Joule effect while running. The method has a nanometric resolution for the displacement measurement and is based on the analysis of the speckle structure of the device while illuminated by coherent light. A high-resolution interferometer is also used to record the transient behavior of the normal surface displacement of a point of the surface. These optical approaches provide interesting quantitative information about strain and stress in electronic power devices and allow testing of finite element simulations. These techniques can be compared to Moire thermomechanical studies but with better resolution and sensitivity. (C) 1999 Elsevier Science Ltd. All rights reserved.