Neutron Hardness Assurance of Bipolar Transistors by Collector Resistance Determination

An approach to neutron hardness assurance in bipolar transistors is described, based on an observed high correlation of post-irradiation, saturated current gain with pre-irradiation collector resistance. Two experiments are described in which the correlation of post-irradiation gain is determined, first, with a set of structural parameters measured on auxiliary test patterns on the same chip with the subject transistor and, second, with electrical parameters measured at the terminals of the subject device. Results of these experiments suggest the feasibility of using collector resistance as a single hardness screening parameter. Implementation of this approach requires incorporation of an auxiliary resistor structure on each transistor chip and determination of the resistor value acceptance limit for the neutron fluence of interest.