Effects of device scaling and geometry on MOS radiation hardness assurance

The effects of transistor scaling and geometry on radiation hardness are investigated. The total-dose response is shown to depend strongly on transistor channel length. Specifically, transistors with shorter gate lengths tend to show more negative threshold-voltage shifts under irradiation than transistors with longer gate lengths. Similarly, transistors with longer gate lengths tend to show more positive threshold-voltage shifts during postirradiation annealing. It will be important to factor these differences in radiation response into test-structure-to-IC correlations necessary to support cost-effective qualified manufacturers list hardness assurance. Transistors with minimum gate length will have a larger effect on standby power supply current for an IC at high dose rates, such as in a weapon environment, where worst-case response is associated with negative threshold-voltage shifts during irradiation. On the other hand, transistors with maximum gate length will have a larger effect on the timing parameters of an IC at low dose rates, such as in a space environment.>