Research On The Damage Effect And Mechanism Of Bipolar Transistor Caused By Microwaves

With the development of pulse power technology, the electromagnetic environment is deteriorating due to high-power microwave (HPM) generated by various pulse power sources, and the electronic systems become more susceptible to interference and damage induced by HPM. Being the essential parts of the electronic systems, semiconductor devices can be disrupted, confused, or damaged by the intentional and unintentional HPM from the external environments. Meanwhile, the semiconductor devices become more sensitivity and vulnerability due to the tendency of high integration, low power consumption, high performance and high reliability. Usually, there are two classic technological approaches exploring HPM effects and determining certain disrupted or burnout parameters of HPM, one of them is test research, and the other is theory research. Due to the restriction of varieties of device types and the complexity of electronic systems and the electromagnetic environments, the huge budgets and inadequate theoretical supports are the major problems to the test research. Therefore, the theoretical study of the effect and mechanism of semiconductor devices is of great practical significance.In this thesis we establish a two-dimensional (2D) electro-thermal model of the typical silicon-based n+-p-n-n+structure bipolar transistor induced by HPM, obtain the effect and mechanism of the device caused by HPM, and study the influences of microwave parameters on the device damage process and some hardening measures against microwave-induced damage. The main studies and conclusive results are as follows:1. With a consideration of self-heating effects, mobility degradation in high electric fields and avalanche generation effects, a two-dimensional electro-thermal model of the typical silicon-based n+-p-n-n+structure bipolar transistor induced by HPM is established in this thesis. By analyzing the variations of device internal distributions of the electric field, the current density and the temperature with time, a detailed investigation of the damage effect and mechanism of the bipolar transistor under the injection of1GHz equivalent voltage signals from the base and collector is elaborated. The results show that temperature elevation occurs in the negative half-period and the maximum temperature falls slightly in the positive half-period when the signals are injected from the collector. Compared to the former, device damage occurs more with the signals injected from the base. Specifically, the base-emitter juncti susceptible to damage. The damage results caused by two large-amplitude signal initial phase of0and π respectively indicate that the injected signal with initial phase of π is more liable to cause device damage. The theoretical model calculation results and the test results are in good agreement.2. Based on the2D electro-thermal model of bipolar transistor, a theoretical study of the pulse width effects on the damage progress of the bipolar transisitor caused by HPM is presented through the injection approach. The relationship between the microwave damage power P, the absorbed energy required to cause the device failure E and the pulse width τ are obtained in the nanosecond region utilizing the curve fitting method. Meanwhile, a comparison of microwave pulse damage data and the existed dc pulse damage data for the same transistor is carried out. By means of two-dimensional simulator ISE-TCAD, the internal damage progress of the device caused by microwave voltage signals and dc pulse voltage signals respectively is analyzed comparatively. The simulations suggest that the temperature-rising positions of the device induced by the microwaves are different between negative and positive half-period while only one hot spot exists under the injection of dc pluses. The comparisons demonstrate that the microwave damage power threshold and the absorbed energy must exceed the dc pulse power threshold and the absorbed energy and the dc pulse damage data may be quite useful as a lower bound for microwave pulse damage data.3. A theoretical study of the damage susceptibility trend of the typical bipolar transistor induced by HPM as a function of frequency is conducted. The dependences of the burnout time and the damage power on the signal frequency are obtained. A study of the internal damage process and mechanism of the device is carried out from the variation analysis of the distribution of the electric field, the current density and the temperature. The investigation shows that the burnout time is linearly depend on signal frequency. The current density and the electric field at the damage position decrease with the increasing frequency. Meanwhile, the temperature elevation occurs in the area between the pn junction and the n-n+interface due to the increase of the electric field. Adopting the data analysis software, the relationship between the damage power and the frequency is obtained.4. A theoretical study of the thermal accumulation effect of the typical bipolar transistor caused by HPM is carried out, and the thermal accumulation effect as function of the pulse repetition frequency (PRF) and the duty cycle is investigated. A study of the damage mechanism of the device is carried out from the variation analysis of the distribution of the electric field and the current density. The research shows that the accumulation temperature increases with the increasing PRF and the threshold for the transistor is about2KHz. The response of the peak temperature injected by the single pulses indicates that the falling time is much longer than the rising time. Adopting the fitting method, the relationship between the peak temperature and the time during the rising edge and the falling edge is obtained. Moreover, the accumulation temperature decreases with the increasing duty cycle for a certain mean power.5. By analyzing the variations of the internal distributions of the temperature with time and the current density and the burnout time with the signal amplitude, a study of the internal damage process and mechanism of the bipolar transistor induced by three kinds of HP Ms such as triangular wave, sinusoidal wave and square wave is carried out. The results show that the base-emitter junction is the damage position and the device is more susceptible to damage under the injection of the square waves. The displacement current and the burnout time increase but the proportion of the displacement current in the total current decreases with the increasing signal amplitude. The injected power play a determinative role in the damage process compared with the displacement current. Adopting the data analysis software, the relation equation between the burnout time t and the signal frequency fis obtained. It is demonstrated that the burnout time increases with the increase of the signal frequency.6. The influence of the bias voltage and the external components on the damage progress of the bipolar transistor induced by HPM is studied. The mechanism is presented by analyzing the variations of device internal distributions of the temperature. The findings show that the device becomes less vulnerable to damage with the increasing bias voltage. Both the series diode at the base and the relatively low series resistance at the emitter resistance Re can make the burnout time of the device increase obviously. However, Re will aid the damage of the device when the value is sufficiently high due to the fact that the highest hot spot shifts from the base-emitter junction to the base region. Moreover, the series resistance at the base resistance Rb will weaken the capability of the device to withstand microwave damage.