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 e lectronic devices. We have applied it to image the deformation undergone by a MOS power transistor due to its operation. This imaging method allows th e derivation of the three components of. the displacement vector of each po int of the surface of the component while heated by Joule effect while runn ing. The method has a nanometric resolution for the displacement measuremen t and is based on the analysis of the speckle structure of the device while illuminated by coherent light. A high-resolution interferometer is also us ed to record the transient behavior of the normal surface displacement of a point of the surface. These optical approaches provide interesting quantit ative information about strain and stress in electronic power devices and a llow testing of finite element simulations. These techniques can be compare d to Moire thermomechanical studies but with better resolution and sensitiv ity. (C) 1999 Elsevier Science Ltd. All rights reserved.