Enhanced Low Dose Rate Effect (ELDRS) on Linear BiPolar Microcircuits

The radiation hardness community has observed that some types of linear integrated circuits constructed with bipolar integrated transistors degrade more rapidly when irradiated at a much lower dose rate then conventionally used during radiation hardness testing. The MIL-STD-883, Test Method 1019, standard condition dose rate of 50 to 300 rad(Si)/second is used primarily throughout the industry to baseline the radiation hardness level for devices that may be used in a radiation environment. These same devices, however, when subjected to dose rates below 50 rad(Si)/second, can exhibit significantly lower total dose hardness levels. An electronic system deployed in space can encounter ionizing dose rates of 0.001 rad(Si)/second, or less. This phenomenon is of particular concern because the design margins that enable circuits to tolerate radiation are often based on characterization data obtained at the standard 50 to 300 rad(Si)/second dose rate.

Since data at lower dose rates are not widely available at this time, radiation characterization needs to be performed on linear bipolar devices as they are selected for use in new designs being used in low dose rate environments. The manufacturer of the device should be contacted to obtain any information they may have concerning the effects of low dose rates on their products. Existing systems should evaluate linear bipolar devices for susceptibility to low dose rate effects. A risk assessment should be performed on those devices that exhibit low dose rate effects.