Comparison of ionizing-radiation-induced gain degradation in lateral, substrate, and vertical PNP BJTs

Thermal-stress effects and enhanced low dose rate sensitivity in linear bipolar ICs

“…That unbiased thermal stresses can induce changes in the charge transport andfor trapping properties of the oxides at the die level is consistent with previous work on MOS devices which suggests that the mechanism responsible for the PETS effect is bias independent [13]. Recall that previous work has shown that pre-irradiation elevated temperature stresses can cause increases in oxide-trap change buildup and decreases in interface-trap charge buildup [ 12]- [ 14], both of which act to reduce radiation-induced gain degradation in these types of substrate PNP transistors [6], [11]. We also note that for long stress times, PETS has effectively eliminated any "true" dose rate dependence for total dose up to 10 krad(Si02) in these devices.…”

“…To understand the nature of this interaction, we observe that the application of PETS tends to reduce the amount of postirradiation gain degradation in these devices. This corresponds to an increase in oxide-trap charge and a decrease in interface trap charge in the base oxides of these PNP transistors [6], [11]. Hence, it seems likely that the elevated temperature stresses activate metastable trap sites in the bulk of the oxide (e.g., via the release of hydrogen that had previously passivated the site), thus increasing the range of doses and rates under which space charge fields are significant in the oxide [10], and consequently the region in which true dose rate effects are present in these devices.…”

“…We note that others have also suggested the possibility of delayed interface-trap charge buildup near midgap to explain the ELDRS response @ PNP transistors [6], [11]. Second, the 175°C 100-hour stress appears to have eliminated any true dose-rate effects that may have existed in these devices.…”

60Co γ-ray induced gain degradation in bipolar junction transistors

“…Degradation by ionization is a surface effect and mainly occurs in the oxide passivation layer, particularly the oxide covering the emitter-base junction region. Degradation by ionization (surface degradation) leads to increase in base current due to two mechanisms : (i) the accumulation of trapped charges in the oxides, (ii) the accumulation of interface states at the silicon-silicon dioxide interface [3,4].…”

“…After every accumulated dose, the measurements are made within one minute. Apart from collector characteristics, Gummel plots, log (I C ) vs. V BE and log(I B ) vs. V BE at constant V CE , have also been obtained after every accumulated dose [2][3][4].…”