Test procedures


Parts are exposed at high dose rates denoted with HDR-S (S for switching) to achieve certain degradation levels, with low dose rates denoted with LDR-S (S for switching) to measure segments with of the low dose rate degradation curve, and with a continuous dose rate named LDR-C (C for continuous). Measurements are performed exposing the part types in a biased and unbiased configuration.

Applied test procedures:

High Dose Rate - Switching (HDR-S)
Low Dose Rate - Switching (LDR-S)
Low Dose Rate - Continuous (LDR-C)

High Dose Rate - Switching (HDR-S)

Prior to exposure all devices are electrically characterised shortly before start of the switching experiment. This will ensure that all used devices are in good condition. Devices that perform faulty or significantly different from the average behaviour will be rejected. The switching experiment is done using four dose switches, thus requiring five exposure series. The first exposure series covers the low dose rate degradation curve from zero dose value up to the first dose switch, the second exposure series from the first dose switch to the second, and so on. Each exposure series consists of five units.

The high dose rate exposure is done in parallel for all exposure series, but all of them are exposed to different dose levels. One starts with the last exposure series since this one requires the longest exposure time. After equally distributed time intervals the other exposure series are added one by one to the irradiation boards. To do so the irradiation has to be interrupted to add the additional devices. The interruption of the high dose rate exposure is supposed to be short, and approximately five minutes are sufficient, since the only action to be taken is to mount additional five DUTs on the irradiation boards. In total four exposure series have to be irradiated in parallel. The 1st exposure series is not exposed to HDR-S but only to LDR-S. HDR-S is performed at a dose rate of 1 rad(Si) sec-1, the scheduled time for the exposure is approximately one day.

Low Dose Rate - Switching (LDR-S)

After completion of the HDR-S all units are electrically characterized. After this they will be exposed LDR-S. LDR-S is performed at a dose rate of 10 mrad(Si)/s applying a total dose of 20 krad(Si) to the DUTS. Thus the exposure will last for 23 days. All exposure series are exposed in parallel, of course. Within this period all the units will be electrically characterized three times and once more after the end of the exposure. Thus, in total each unit is characterized five times.

For electrical characterisation the exposure has to be interrupted. The units have to be removed from the facility, being characterized, and re-mounted in the facility. The total time needed for these actions is estimated to be 2 hours.

For the switching tests and one exposure configuration, namely biased or unbiased, 25 DUTs are needed. Thus in total 50 devices are needed of each type for the switching experiments.

Low Dose Rate - Continuous (LDR-C)

As a reference experiment five units of a certain part type are exposed with a continuous low dose rate exposure, named LDR-C. For each part type being tested a reference measurement is performed at a constant low dose rate of 10 mrad(Si)/s. For each part type five units are exposed in biased and unbiased configuration. The total dose level for the irradiation is 100 krad(Si). Characterisation of the DUTs is done prior to exposure and after exposure. During exposure characterisation will be done in regular intervals of approximately every 20 krad(Si) in terms of absorbed dose.