Total-Dose Survival Probability for Bipolar Transistors

Four samples of one hundred devices each were tested. Three transistor types, consisting of 200 of type 2N1613, 100 of type 2N2219, and 100 of type 2N3420, were irradiated under various bias conditions in a Co-60 gamma environment at a rate of 7.6 × 103 Rads(Si) /hour and an ambient temperature of 25°C. Data are presented in terms of percent failure versus dose [up to 5.8 × 105 Rads(Si)] for a family of failure criteria and for a family of measurement conditions. It is concluded that 1) the Weibull distribution seems to be adequate as a means of predicting low-dose survival probability if care is taken to fully characterize the one or more distributions present. For the devices studied, there is not a minimum value for darnage threshold; however, in two device types there does appear to be either more than one failure mode present or else two distributions. 2) the Weibull technique can be used to indicate manufacturing variations in device lots and, when combined with parameter frequency charts, may provide a screening technique or a monitor on the quality of semiconductor device surfaces. 3) ionizing radiation may in many cases be the dominant environmental component to consider when projecting component and system reliability since 0.1 percent failure probabilities can occur at doses of the order of 103 rads. 4) operating conditions during irradiation have a significant effect on the reliability of at least the 2N1613 device type.