Absorbed Energy
Measure of the total amount of energy deposited by ionizing radiation into a material, usually expressed in units of gray or rad. Accumulation of total ionizing dose leads to the gradual degradation of oxide layers and interfaces in microelectronic components. This effect results in shifts in the threshold voltage and increases in the leakage current of transistors.
Dose Rate
Time over which the radiation is delivered influences the resulting damage. In many space missions, the total ionizing dose builds up at a very low rate, which may allow for partial self-healing of the material. Laboratory tests often use higher rates to accelerate the qualification process.
This acceleration requires careful correlation with real-world behavior. Technicians must adjust for these differences during the analysis phase.
Shielding Mitigation
Placing high-density materials around sensitive electronics reduces the amount of radiation that reaches the silicon. Designers calculate the expected total ionizing dose behind various thicknesses of aluminum or tantalum to optimize the weight of the spacecraft. These calculations must account for secondary radiation produced within the shield itself.
Hardness Level
Components are rated based on their ability to survive specific exposure levels without failing. If the predicted total ionizing dose for a mission exceeds the rating of the chosen part, designers must find a more resilient alternative or increase the shielding.
