Total ionizing dose (TID)
Beginner
All the radiation a chip soaks up over its life. It slowly wears the chip out.
Novice
The total amount of radiation a chip absorbs over its life, measured in krad (thousands of rad, a unit of absorbed energy). It slowly changes how the transistors behave until the chip drifts out of spec or stops working.
Expert
Charge trapped in the transistors’ gate oxide shifts their threshold voltage and raises leakage current. A spec states it as a minimum tolerance, for example 300 krad(Si), where “(Si)” means energy absorbed per kilogram of silicon. Enclosed-layout transistors, whose gate surrounds one terminal, raise the tolerance further.