Radiation damage effect and post-annealing treatments of NPN-input bipolar operational amplifier in electron radiation environment

Abstract

With the rapid development of the space technology, operational amplifier is widely used as the basic liner circuit in a satellite system. There are many charged particles trapped in the earth's magnetosphere, most of the particles are protons and electrons. In BJTs, the damage caused by electrons causes both bulk recombination and surface recombination to increase and subsequently current gain to decrease. Transistor gain degradation is the primary cause of parametric shifts and functional failures in linear bipolar circuits. The severity of electron radiation response correlates with electron's energy and flux, therefore it is important to understand the electron radiation response in different conditions. In this paper, the tested devices used in this study are NPN-input bipolar operational amplifiers commercial-off-the-shelf (COTS) manufactured by Texas Instruments (TI). NPN-input bipolar operational amplifiers LM108 are irradiated with different energy and different beam current electrons respectively under different bias conditions to study the electron radiation damage effect. Experiment using 60Coγ-ray radiation is conducted to compare the different radiation damages between 60Coγ-ray and electron radiation. The total radiation experiments are carried out with the 60Coγ-ray source (Xinjiang Technical Institute of physics and chemistry). The radiation dose rates for the test samples are 1 Gy (Si)/s, and the total accumulated dose is 1000 Gy (Si). Subsequently, room temperature and high temperature annealings are conducted to analyze the parametric failure mechanism of LM108 caused by a total dose radiation for different biases. Result shows that 0.32 Gy(Si)/s beam current electrons can induce more damage than that caused by 1.53 Gy(Si)/s electrons with the same energy; 1.8 MeV electrons can induce more damages than 1 MeV electrons with the same electron beam current because the former produces more displacement damage than the latter. Comparison between zero and forward biased devices shows that different biased devices have different radiation sensibility, and radiation produces more damages in zero biased devices than in forward biased devices with the same electron energy and beam current. This is because forward biased BJT will suppress the edge electric field, thus leading to the decrease of oxide-trapped charge and interface-trapped charge. During high-temperature annealing, degradation of the devices obviously can be recovered and almost return to the initial value finally. This result indicates that the 1.8 MeV and 1 MeV electron radiation mainly induces ionization damage in bipolar operational amplifier LM108.