Charge Yield at Low Electric Fields: Considerations for Bipolar Integrated Circuits

A significant reduction in total dose damage is observed when bipolar integrated circuits are irradiated at low temperature. This can be partially explained by the Onsager theory of recombination, which predicts a strong temperature dependence for charge yield under low-field conditions. Reduced damage occurs for biased as well as unbiased devices because the weak fringing field in thick bipolar oxides only affects charge yield near the Si/SiO₂ interface, a relatively small fraction of the total oxide thickness. Lowering the temperature of bipolar ICs-either continuously, or for time periods when they are exposed to high radiation levels-provides an additional degree of freedom to improve total dose performance of bipolar circuits, particularly in space applications.