HEMT器件电磁脉冲毁伤机理仿真分析及试验研究
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作者:安宁 柴常春 刘彧千
摘 要:以强电磁脉冲为典型代表的复杂电磁环境对雷达前端关键模块与器件的可靠性不断构成威胁。本文对雷达前端电路中低噪声放大器的关键器件——GaAs HEMT进行了强电磁脉冲效应仿真研究与试验验证。利用仿真软件构建了GaAs HEMT的二维热电模型,并对器件栅极注入强电磁脉冲的情况进行了仿真,研究发现,该注入条件下器件内部峰值温度呈现周期性的上升-下降-上升-下降趋势,最终达到GaAs的熔点温度, 导致器件烧毁,烧毁位置在栅极下方偏向源极的位置。通过对低噪声放大器芯片进行注入实验和剖片分析,在TEM显微镜下观察到GaAs HEMT器件栅极下方靠近源极的区域有明显烧毁,与仿真结果相符。通过对仿真数据的处理和拟合,总结了器件烧毁功率阈值和能量阈值与注入微波脉宽的关系,得出器件烧毁的功率阈值随着脉宽的增大而减小,能量阈值随着脉宽的增大而增大,与经验公式相符。
关键词: 低噪声放大器;强电磁脉冲;HEMT器件;功率阈值;能量阈值; 电磁毁伤
中图分类号:TJ95; TN959.73 文献标识码:A 文章编号:1673-5048(2020)03-0088-05
0 引言
毫米波低噪声放大器芯片应用于毫米波雷达的前端电路中,对经过的高频小信号起到放大作用,通常前端电路直接与外部天线相连,因此更容易受到强电磁脉冲的干扰与打击。GaAs HEMT器件由于技术成熟、成本较低,同时又有着较好的低噪声放大性能,所以被广泛用于毫米波低噪声放大器芯片中。在强电磁脉冲的干扰下[1],如果GaAs HEMT器件发生毁伤,会导致整个雷达前端电路的功能发生退化。
近年来,针对不同类型半导体器件的电磁脉冲毁伤效应研究已受到广泛的关注。对于双极型晶体管,文献[2-5]分别针对器件基极、集电极、发射极的强电磁脉冲的损伤机制以及对于功率频率等不同脉冲参数对器件损伤的影响进行了一系列的理论分析、效应仿真和实验研究。同时,文献 [6-10]对数字集成电路中CMOS器件的强电磁脉冲的损伤效应、闩锁效应以及强电磁脉冲注入下产生的位翻转和特性退化,以及功率脉宽等因素对于器件损伤效应的影响进行了研究。
本文研究了强电磁脉冲注入下GaAs器件的损伤效应及机理[11-12],通过Sentaurus-TCAD仿真软件建立了典型GaAs HEMT的二维热电模型,并将强电磁脉冲以正弦信号的形式注入器件的栅极,通过对器件内部电场强度、电流密度和温度随时间的变化情况进行分析,得到了HEMT器件的损伤机理。 将仿真结果与TEM下观察到的实际剖片结果进行对比,得到良好的一致性。最后,通过对数据的处理和拟合,分别得到了器件在电磁脉冲注入下,毁伤功率阈值和能量阈值与脉冲脉宽之间的关系。
1 器件模型建立
1.1 器件结构模型
典型GaAs pHEMT结构如图1所示,包括:半绝缘GaAs衬底;InGaAs沟道;Delta掺杂区,可以让量子阱更深,二维电子气浓度更高;i-AlGaAs层,减少电离杂质对二维电子气的影响;n-AlGaAs层,为InGaAs沟道中的二維电子气提供电子;中间及两端顶部深色区域为金属电极。
利用半导体仿真软件Sentaurus-TCAD建立了与图1结构相同的0.15 μm HEMT器件结构图,如图2所示。器件竖直方向的尺寸从上到下分别为50 nm Si3N4钝化层,30 nm GaAs 帽层,34.5 nm AlGaAs阻挡层,10 nm InGaAs沟道。横向的尺寸分别为0.05 μm的源极(漏极和源极为左右对称结构), 0.15 μm的栅极。器件的掺杂从图2中可以看出。
1.2 器件物理模型
Sentaurus-TCAD仿真软件通过数值迭代求解泊松方程、电流连续性方程和热载流子方程来模拟计算器件内部微观结构的电、热学特性。在强电磁脉冲的注入下,器件内部的温度会发生剧烈变化,因此,需要在一般载流子输运方程上再考虑温度对电流密度的影响:
式中: Jn,Jp分别为电子和空穴的电流密度;n,p分别为电子和空穴的密度;μn,μp分别为电子和空穴的迁移率;Pn,Pp分别为电子和空穴的绝对热电功率;Фn,Фp分别为电子和空穴的准费米能级;q为电子的电量;T为温度。
由于器件会产生自热效应,为了求解器件内部的温度分布情况,还需要考虑热传导方程[13]:
式中: c为晶格热熔;k为热导率;EC,EV分别为导带底和价带顶的能量;kB为玻尔兹曼常数;R为复合率。
1.3 器件直流特性
为了验证仿真模型可以正常工作,分别对器件的开启特性曲线和输出特性曲线进行了仿真。
漏极电压为恒定2.5 V时,对器件进行开启特性的仿真,如图3所示。
从图3中可以看出,器件为典型的耗尽型HEMT器件,对器件的开启特性曲线进行反向延长,与横轴的交点可以得到器件的开启电压Vgsoff约为-1.4 V。
对器件的输出特性曲线进行仿真如图4所示。图中给出了栅压-0.8~0.8 V步长为0.4 V的5种不同栅压下的器件输出特性曲线,从图中的标注可以看出,当器件工作在Vgs=0 V,Vds=2 V时,器件的工作电流约为0.7 μA。
2 器件强电磁脉冲效应机理分析
仿真电路如图5所示。由图中可以看出,器件漏极接2 V的正电压,栅极处于零偏状态。在仿真条件上,设置器件的衬底为理想热沉,初始仿真温度设置为室温(300 K)。由于器件内部主要由GaAs组成,所以设置当
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Simulation and Experimental Study on Damage Mechanism of
Electromagnetic PulseofHEMT Device
An Ning1*,Chai Changchun2,Liu Yuqian2
(1. China Airborne Missile Academy,Luoyang 471009, China;2. Xidian University,Xi’an 710126, China)
Abstract: The complex electromagnetic environment represented by electromagnetic pulses is a constant threat to the reliability of key modules and devices in the radar front end. In this paper, the simulation and experimental verification of the strong electromagnetic pulse effect are performed for the GaAs HEMT, which is a key component of the low-noise amplifier in the radar front-end circuit. The two-dimensional thermoelectric model of GaAs HEMT is constructed by using simulation software, and the injection of electromagnetic pulse to the gate of the device is simulated. It is found that the peak temperature inside the device exhibits a periodic rise-fall-rise-fall trend under the injection condition, and the final temperature will reach the melting point of GaAs, leading to burnout, which is locatedbelow the gateclosed to the source. Through the injection experiment and the slice analysis of the low-noise amplifier chip, it is observed that the area near the source of the gate of the GaAs HEMT device is burnt
under the TEM microscope, which is in good agreement with the simulation results. Through the processing and fitting of the simulation data, the relationship between burnout power threshold and injection microwave pulse width and the relationship between burnout energy threshold and injection microwave pulse width are analyzed. It can be concluded that the power threshold of the device burnout decreases with the increase of the pulse width, and the energy threshold increases with increasing pulse width,which is consistent with empirical formulas.
Key words: low noise amplifier; electromagnetic pulse; HEMT device; power threshold; energy threshold; electromagnetic damage
收稿日期: 2019-09-14
基金項目: 航空科学基金项目(2018ZC12006)
作者简介: 安宁(1985-),女,河南洛阳人,高级工程师,硕士,研究方向是高功率微波技术。
E-mail: guoguo6522@163.com
引用格式: 安宁,柴常春,刘彧千.HEMT器件电磁脉冲毁伤机理仿真分析及试验研究
[ J].
航空兵器,2020,27( 3): 88-92.
An Ning,Chai Changchun,Liu Yuqian. Simulation and Experimental Study on Damage Mechanism of Electromagnetic PulseofHEMT Device[ J]. Aero Weaponry, 2020, 27( 3): 88-92.( in Chinese)
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