【作者】 任兴荣；

【导师】 柴常春；

【作者基本信息】 西安电子科技大学 ， 微电子学与固体电子学， 2014， 博士

【摘要】 电磁脉冲炸弹和高功率微波武器等新概念电子战武器的快速发展以及雷达和无线通信系统的广泛使用使得电子系统面临的电磁环境日益复杂化，另一方面半导体器件和集成电路特征尺寸的不断缩小、功耗的不断降低以及工作频率的不断提高使得电子系统对电磁能量的敏感度和易损性与日俱增，因此研究电磁脉冲(electromagnetic pulse, EMP)对电子系统的干扰和损伤效应进而提高电子系统的抗干扰能力变得越来越重要。电磁脉冲可通过天线、电缆和孔缝等耦合进入电子系统内部，引起半导体器件的退化或损伤。因此研究EMP对半导体器件的损伤效应与机理是电子系统EMP效应研究的基础。本论文采用半导体器件数值仿真与实验相结合的方法，研究了几种典型半导体器件的EMP损伤效应与机理，主要的研究内容和研究成果包括以下几个方面：1.采用半导体器件和工艺仿真工具ISE-TCAD建立了p-n-n+二极管的二维数值仿真模型，考虑了器件的自热、雪崩碰撞电离等效应，对EMP作用下二极管的烧毁过程进行了瞬态电热仿真，分析了二极管内部的电场强度、电流密度和温度分布的瞬时变化，讨论了影响二极管烧毁的因素，计算了二极管的损伤能量阈值。仿真结果表明，二极管烧毁是由热二次击穿导致的。雪崩产生率随温度升高而减小以及热产生率随温度升高而增大是热二次击穿发生的根本原因，二次击穿后二极管表现出的负阻效应导致电流集中，使二极管局部温度迅速升高，从而引起二极管烧毁。二次击穿触发温度随二次击穿延迟时间增加而降低，随载流子寿命增大而升高。仿真得到的二极管损伤能量阈值随脉冲宽度的增加而增大，脉宽较短时，损伤能量近似为一常数，脉宽较长时，损伤能量与脉宽的平方根近似成正比，与现有热模型一致。与实验数据的定量比较结果表明，仿真得到的能量阈值比热模型的预测更精确。2.建立了PIN限幅二极管的二维电热仿真模型，研究了其在EMP作用下的瞬态响应，分析了电流丝形成及运动机理，讨论了电流丝运动方式及其对PIN二极管损伤的影响。结果显示，PIN二极管发生雪崩击穿后由于空间电荷产生的负阻效应引起的不稳定性致使I层内形成雪崩电流丝，局部温度迅速升高。雪崩电离率的负温度系数驱使雪崩电流丝向低温区运动，电流丝运动促使器件I层内的横向温度分布趋于均匀，避免因局部过热而导致器件快速烧毁。电流丝到达器件边缘后温度迅速升高，若低于临界温度，电流丝沿原路返回或跳跃到低温区；若超过临界温度，雪崩电流丝转变为热电流丝，被钉扎在器件边缘，温度升高的同时不断收缩，导致PIN二极管局部烧毁。在亚微秒脉宽内，损伤能量随脉宽减小呈下降趋势，电流丝形成位置的不确定性致使PIN二极管损伤能量表现出一定的离散性。3.针对典型高频小信号双极型晶体管(BJT)，建立了其二维电热模型，研究了强电磁脉冲从基极注入时BJT的瞬态响应。结果表明，BJT的损伤机理与脉冲幅度有关，低脉冲幅度下BJT损伤是由于发射结发生雪崩击穿导致局部烧毁，烧毁点位于发射结边缘的柱面区；而在高脉冲幅度下，基区-外延层-衬底组成的p-n-n+结构发生了二次击穿，导致靠近发射极一侧的基极边缘由于电流密度过大而先于发射结烧毁；BJT损伤能量随脉冲幅度升高呈现减小-增大-减小的变化趋势，存在一个最小值。与实验结果的对比表明，本文的模型能够准确模拟EMP作用下BJT的烧毁过程。4.开展了两级级联低噪声放大器(LNA)高功率微波前门注入效应实验，研究了其性能退化及功能损伤效应和阈值，对失效LNA进行了破坏性失效分析。结果显示，当注入信号功率超过一定值时，LNA的噪声系数明显增加，增益也有所下降，性能退化；当信号功率继续增加到某一临界值时，LNA的噪声系数和增益严重恶化，功能完全丧失。LNA损伤功率阈值随注入脉冲宽度减小而增大。LNA退化或损伤是由第一级晶体管退化或损伤导致的。GaAs HEMT退化机理为注入信号作用下栅极金属与GaAs相互扩散引起栅金属下沉导致栅-源/漏肖特基结退化，表现为栅-源/漏肖特基结反向漏电、正向导通电压降低；晶体管损伤机理与注入信号形式有关：连续波或微秒级脉冲注入时晶体管损伤机理为栅-源反向击穿，表现为栅-源/漏短路；亚微秒级脉冲注入时晶体管栅-源和栅-漏均发生了反向击穿，表现为栅-源/漏短路；纳秒级脉冲注入时晶体管损伤机理为栅金属化烧毁，表现为栅-源/漏呈电阻特性。更多还原

【Abstract】 The electromagnetic environment of electronic systems is deterioratingincreasingly due to the rapid developments of new concept electronic warfare weaponslike electromagnetic pulse bombs and high-power microwave weapons as well as theextensive applications of radars and wireless communication systems. On the otherhand, semiconductor devices and integrated circuits are characterized by smaller featuresizes, lower power dissipation and higher operating frequency, which increases thesusceptibility and vulnerability of electronic systems to electromagnetic energies.Therefore, it becomes more and more important to study the interference and damageeffects of electronic systems induced by electromagnetic pulses (EMPs) so as toimprove the immunity of electronic systems to EMPs. EMPs can be coupled intoelectronic systems through antennas, cables, apertures and so on, thus resulting in thedegeneration or destruction of semiconductor devices. Hence, the research on damagemechanisms of semiconductor devices caused by EMPs is the basis of research onEMP-induced effects of electronic systems.In this dissertation the damage effects and mechanisms of several typicalsemiconductor devices induced by EMPs are studied by numerical simulations andexperiments with the following research results:1. A two-dimensional (2D) model of a typical high-frequency small-signal diodewith a p-n-n+structure is established for numerical simulations with self-heating effectsand avalanche generation in consideration. Based on the model, transient electrothermalsimulations are performed to simulate the damage process of diodes induced by EMPs,the variations of the distributions of electric field, current density and temperature insidethe diode with time are analyzed in detail, the factors affecting the burnout of diodes arediscussed, and the damage thresholds are calculated. The results show that the burnoutof diodes is caused by thermal mode second breakdown. The occurrence of thermalmode second breakdown is due to the negative temperature dependence of avalanchegeneration rate and the positive temperature dependence of thermal generation rate.When the diode goes into second breakdown, dynamic negative resistance leads to localcurrent concentration, followed by a rapid local temperature rise and finally the burnoutof the diode. The triggering temperature of second breakdown increases with the carrierlifetime and decreases with the delay time. The calculated damage energy thresholdincreases with the pulse width. For the short pulse, the damage energy is approximately constant, and for the long pulse, the damage energy is nearly proportional to the squareroot of pulse width, which is consistent with the thermal models available. Aquantitative comparison with experimental data shows that the simulated energythreshold is more precise than what is predicted by the thermal models.2. A2D model of a typical PIN limiter diode is established for electrothermalsimulations. The transient response of the PIN diode to EMPs is simulated, the physicalmechanisms of the formation and motion of current filaments are analyzed, and thefilament moving mode and its impact on the damage to the PIN diode are discussed.The results show that the instability induced by the current-controlled negativeresistance of avalanching PIN diodes leads to the formation of avalanche currentfilaments in the I layer of the PIN diode, resulting in a succeeding local temperature rise.The negative temperature dependence of avalanche generation rates drives the filamentto move towards low-temperature regions. The motion of filament homogenizes thetemperature distribution in the I layer, thus preventing the PIN diode burnout due tolocal overheating. When the filament arrives at the edge of the device, the temperatureat the edge rises rapidly, which drives the filament to leave the edge and return or jumpto the low-temperature regions depending on the filament current density andtemperature distribution in the device. When the filament temperature exceeds a criticalvalue, the thermal excitation will replace the impact ionization as the major source ofcarriers, and the positive temperature dependence of thermal generation rates willproduce a thermal-electrical positive feedback inside the filament, which will pin thefilament at the edge of the device, thus shrinking it continuously, making the filamenttemperature rise quickly, and leading to the burnout of the PIN diode. For thesubmicrosecond pulse width, the damage energy decreases as the width decreases, andthe uncertainty of the initial position of filaments will lead to a dispersion in the damageenergy of PIN diodes.3. For a typical high-frequency small-signal bipolar junction transistor (BJT), a2Delectrothermal model is established to study the damage mechanism and damagethreshold of the BJT under the injection of the EMP at the base. The results show thatthe damage mechanism of the BJT is related to the pulse amplitude: for a low pulseamplitude, BJT damage is caused by the local burnout at the edge of the base-emitterjunction due to avalanche breakdown, and for a high pulse amplitude, a secondbreakdown in the base-epitaxy-substrate p-n-n+structure results in the local burnout atthe edge of the base neighbouring the emitter before the burnout of the base-emitter junction due to a high current density. The BJT burnout time decreases with the increaseof pulse amplitude, while the damage energy has a minimum value in itsdecrease-increase-decrease tendency. A comparison with experimental results showsthat the model in the dissertation can simulate accurately the burnout process of BJTunder the impact of EMPs.4. High-power microwave front-door injection experiments are carried out in thetwo-stage low noise amplifiers (LNAs), performance degeneration and malfunction ofthe LNAs are studied and destructive failure analyses of the failed LNAs are made. Theresults show that when the injection signal power exceeds a critical value, the noisefigure increases dramatically, the gain decreases, and the performance of the LNAdegenerates; when the signal power increases further to another critical value, the noisefigure and gain deteriorate severely and the LNA loses its main function. With thedecreasing pulse width, the damage power threshold of the LNA increases. The LNAdegeneration or damage is attributed to the first-stage transistor degeneration or damage.The degeneration of the GaAs HEMT is due to the gate-source/drain schottky junctiondegeneration caused by the decline of the gate metallization due to the interdiffusion ofthe gate metal and GaAs, and the degeneration is manifested as reverse leakage currentincreasing and forward voltage lowering of the gate-source/drain junction. The damagemechanisms of the GaAs HEMT are related to the signal waveforms: after the injectionof continuous waves or microsecond-duration pulses, the gate-source short circuit willoccur due to the reverse breakdown of the gate-source junction, after the injection ofsubmicrosecond-duration pulses, the gate-source/drain short circuit will happen due toreverse breakdown of both the gate-source and gate-drain junctions, and after theinjection of nanosecond-duration pulses, the gate-source junction behaves as a resistordue to the gate metallization burnout.更多还原