Hardness Assurance for Long-Term Ionizing Radiation Effects on Bipolar Structures

This work assessed the theoretical understanding of long-term ionization effects in semiconductor bipolar devices in support of developing hardness assurance techniques. The principal effort was directed at investigating transistor gain degradation mechanisms by use of models relating semiconductor physical and electrical parameters to surface properties. Ionizing radiation effects on surface properties were used to identify critical physical parameters for use in hardness assurance procedures. Model implications and predictions were then compared with existing data to evaluate accuracy and usefulness. This investigation demonstrated that current theories regarding the surface of bipolar transistors appear to describe the major parameter dependencies if ionizing radiation effects are not considered. It is when radiation effects are incorporated into these theories (models) that fundamental questions arise as to their completeness or validity. Specific questions were found when the surface models originally defined by Reddi and Grove were used to predict the experimental radiation data observed by Sivo. (Author)