Radiation effects and reliability: Physical mechanisms and rate prediction

The reliability challenges for semiconductor devices change significantly as technology scales and new materials are introduced. One of the most important reliability challenges is soft errors produced by ionizing particles. For terrestrial applications, secondary particles produced by neutron interactions and alpha particles emitted from packaging and back-end-of-line materials are the main concerns. Detailed understanding of the physical mechanisms responsible for radiation-induced charge generation is required to predict the rate at which errors will occur. Parametric degradation produced by electrical stress or long-term exposure to ionizing radiation also is an important issue. The physical mechanisms responsible for device-level effects are in some cases similar for radiation-induced degradation and electrically-induced degradation. In particular, interface traps and oxide charge can be generated by either energetic carriers produced by gate and drain biases or by radiation-induced ionization. These effects often involve hydrogen. Shifts in threshold voltage, transconductance, and other device parameters occur in both MOSFETs and HEMTs, but the details depend on the specific defects responsible for the degradation. Methods of predicting the soft-error rate and the stress-induced degradation rate are discussed.