Thermomechanical reliability of microelectronics

The microelectronic devices integrate more and more diverse materials in a complicated three-dimensional structure with feature size from nanometers to meters. The performance leaps of these devices are so attractive; meanwhile the reliability issues become more urgent in semiconductor industry. Among all of the reliability issues, the thermal-mechanical aspect is always one major concern. This dissertation will cover the following key issues. One is the stress concentration that leads to many failure modes. In the microelectronic devices, the integrated diverse materials are of different thermomechanical properties, and usually bonded together to form the sharp features, such as trenches, wedges, corners or junctions. These sharp features can concentrate stresses, which in turn fail the devices in the ways of cracking, debonding, or injecting dislocations, etc. Therefore, the study of the singular stress filed around the sharp features should draw a lot of attention. Usually, the singular stress field is a linear superposition of two modes, one stronger and the other weaker, known as split singularities. A dimensionless parameter, called the local mode mixity, is defined to charac