【作者】 胡辉勇；

【导师】 张鹤鸣；

【作者基本信息】 西安电子科技大学 ， 微电子学与固体电子学， 2006， 博士

【摘要】 微波功率晶体管对军事电子系统中固态发射机的功能、性能及应用范围起到了重要的推动和支撑作用。对L及其以下波段的固态发射机,Si BJT(双极晶体管)是首选器件,但是Si BJT的微波功率、增益及效率随工作频率的升高而急剧下降,使其频率应用范围受到限制。GaAs器件频率特性好,增益和效率高,在S波段以上被采用,然而它的功率密度较低,成本较高,限制了应用。SiGe HBT(异质结双极晶体管)功率特性与Si BJT相当,频率特性远优于SiBJT。不但可以在S及其以下波段替代Si BJT,而且可以其优良的功率增益和效率等特性替代GaAs HBT应用到Si BJT难以胜任的S以上波段。同时,SiGe HBT应用于固态发射机,还可以提高其性能,使雷达等系统的设计和应用更加灵活。S波段功率晶体管研制和生产的难度是国内外所公认的。目前,国外S波段100W级Si BJT已经商品化,SiGe HBT还处于探索阶段。国内S波段100W级Si BJT技术尚待成熟,SiGe HBT尚未涉足。本论文对S波段功率SiGe HBT理论和技术进行了开拓和探索性的研究工作,设计并研制出了S波段100W SiGe HBT。论文主要开展了以下研究工作：1) SiGe材料的物理参数模型基于SiGe HBT器件结构设计和电学特性研究,建立了表征SiGe HBT交、直流特性所需的SiGe材料物理参数模型,其中包括SiGe材料禁带宽度模型、有效态密度模型、本征载流子浓度模型、重掺杂禁带变窄模型、迁移率模型以及基区中Ge和杂质分布模型等。2)微波功率SiGe HBT直流参数模型基于Si/SiGe异质发射结,建立了发射结电流注入比模型。基于SiGe HBT结构及其物理参数,建立了影响电流增益的基区空穴反注入电流模型,中性基区复合电流模型,空间电荷区俄歇复合电流模型以及空间电荷区SRH(肖克莱-里德-霍尔)复合电流模型,在此基础上建立了电流增益模型。同时在建立了SiGe HBT集电极电流密度模型基础上,建立了基区扩展临界电流密度模型。对电流增益和基区空穴反注入电流、集电极电流及基区扩展临界电流密度等进行了模拟分析。3)微波功率SiGe HBT交流参数模型建立了SiGe HBT特征频率和功率增益模型。频率特性主要由发射极延迟时间、基区渡越时间、集电结耗尽层延迟时间和集电极延迟时间决定。为此,在研究分析可动电荷对势垒电容影响的基础上,建立了SiGe HBT发射结势垒电容和集电结势垒电容模型,并据此建立了包括基区扩展效应在内的发射极延迟时间模型。建立了SiGe HBT基区渡越时间模型,该模型考虑了电流密度及基区掺杂和Ge组分所引起的各种物理效应,适于基区掺杂和Ge组分为均匀和非均匀分布,以及器件在小电流到大电流密度下的应用。建立了适于Ge组分不同剖面分布的SiGe HBT基区渡越时间模型,通过模拟分析获得了最小基区渡越时间的Ge组分剖面分布函数。建立了不同集电极电流密度、包括基区扩展效应条件下的集电结耗尽层延迟时间模型。基于集电区有效宽度,建立了集电极延迟时间模型。并对以上模型进行了模拟分析。4)微波功率SiGe HBT等效电路模型SiGe HBT等效电路更能够体现器件微观结构对器件的电学特性的影响。基于SiGe HBT的器件物理,在分析研究SiGe HBT微观结构、工作机理和载流子分布及输运的基础上,建立了考虑SiGe HBT各种效应(包括厄利效应、速度饱和效应、基区扩展效应及自热效应等)的大信号等效电路模型以及相应的参数模型。该模型物理意义清晰,拓扑结构简单。通过PSpice软件器件方程开发包DEVEQ,将该模型嵌入PSpice软件中,实现对SiGe HBT器件的模拟分析。对器件的交直流分析结果与理论分析结果相一致,并且与文献报道的结果符合得较好。5)微波功率SiGe HBT结构优化根据S波段100W SiGe HBT电学参数设计要求,基于SiGe材料的物理参数、SiGe HBT异质结构以及器件的实现工艺,优化了器件发射区、基区和集电区的厚度、掺杂浓度、Ge组分及分布等纵向结构参数。优化了器件发射区的长度、宽度,基区与发射区的间距,发射极镇流电阻以及多层金属化电极的结构等横向结构参数。得到了优化的发射区和基区的面积比。6)微波功率SiGe HBT工艺设计与实现根据SiGe HBT频率和功率的设计要求,以及应变SiGe材料特殊的制备工艺,优化了制备SiGe HBT芯片的工艺流程。建立了离子注入工艺中目标浓度和深度的估算模型。基于器件的结构参数,优化并实现了浅结的离子注入和快速退火工艺。基于SiGe HBT大电流的工作条件,优化了器件的多层金属化结构(Pt/Ti-W/Pt/Au),实现了多层金属化结构的溅射、电镀及反溅等工艺。通过流片试验,制备出了功率SiGe HBT管芯,并进行了测试,测试结果如下：BVEBO=6.5V, BVCBO=75V, BVCEO=35V,β~25。7)微波功率SiGe HBT内匹配与功率合成建立了S波段功率SiGe HBT管芯输入输出阻抗模型,并对器件管芯的输入输出阻抗进行了估算。优化了S波段功率SiGe HBT的输入输出匹配网络,研究了匹配元件和匹配网络对器件性能的影响。建立了金属引线电感量模型及金属引线间的互感模型。研究了多胞芯片的功率合成技术及功率分配不均匀现象的成因,建立了功率偏差模型。在前述研究工作的基础上,在国内首次研制出了S波段100W SiGe HBT器件,经测试分析,器件达到设计要求,测试结果如下：工作电压30V；工作频率2.7GHz--3.1GHz；脉冲占空比1%--5%；输出功率>100W；功率增益=5dB。更多还原

【Abstract】 In the military electronic system, the microwave power transistor plays an important role in promoting and underpinning the performance and application of solid transmitters. The Si BJT (Bipolar Junction Transistor), applied in transmitters below L band, is the first choice, but the RF power, gain and efficiency of Si BJT are acutely decreasing with the increasing of work frequency, which limits its application on high frequency. The GaAs HBT’s frequency characteristics is good, its gain and efficiency are high, and is adopted in S-band and beyond. But its power density is low, in addition to its high cost, which limits its applications.SiGe HBT (Heterojunction Bipolar Transistor) holds a similar power characteristic to Si BJT and also has a much superior frequency characteristic than Si BJT does. SiGe HBT could not only replace the Si BJT in S-band and under, and could also replace GaAs HBT up to S-band, since it holds good characteristics of power, gain and efficiency, in which condition Si BJT could not work. SiGe HBT could be sued to improve the performances of the solid transmitters, and the could help radar system to get more flexible design and application. The difficulty of development and fabrication of S-band power transistor is widely acknowledged in the domestic and overseas. At the present time, the technology of S-band 100W Si BJT have been commercialized and technology of SiGe HBT is still in the coures of exploration developing. While in domestic, technology of S-band 100W of Si BJT is developing, and the technology of SiGe HBT has not yet steped in.In this disseration, technologies and theories of S-band power SiGe HBT are thoroughly developed. The research work holds exploration, and is a novel research field. The S-band 100W SiGe HBT is developed. The main area and contents of this disseration are as follows.1) Models of physical parameterBased on the design of SiGe HBT structure and study of electrical characteristics, the models of physical parameters of SiGe material are established, which character DC and AC characteristics of SiGe HBT, and they includ the model of forbidden band width, the model of availability state density, the model of intrinsic carrier concentration, the model of mobility, the model of forbidden band becoming narrow by heavy doping, the model of Ge and impurity profile in the base of SiGe material, and so on.2) Model of DC parameter on microwave power SiGe HBTBased on the hetero-emitter-junction of Si/SiGe, the model of emitter junction current injection ratio is established. Based on the structure characteristic and physical parameter of SiGe HBT, the models of the hole reversed injection current, the neutral base region recombination current, the space-charge region Augre recombination current and the space-charge region SRH (Shockley-Read-Hall) recombination current are established, on the basis of which the model of current gain is established. And combining all models, the model of the base extending critical current density of SiGe HBT is setup. And the models of current gain, the hole reversed injection current, the collector current density and base extending critical current density of SiGe HBT are simulated and analyzed.3) Model of AC parameter of microwave power SiGe HBTThe model of frequency characteristic and the model power gain are established. The frequency characteristic is dominated by the sum of emitter delay time, the base transit time, the collector depletion-layer transit time and the collector transit time. Based on study and analyse of influence of mobil charge on capacitance, the model of the emitter junction barrier capacitance and the model the collector junction barrier capacitance are established. And on the basis of these, the model of the emitter delay time is established, including base extending effect. The model of the base transit time is established. Various physical effects caused by doping and Ge fraction in base and current density are considered in the model. The model is suitable for uniform and exponential base doping with different Ge profiles in the base, and different current densities. An analytical model for the base transit time in SiGe HBT with an arbitrary base Ge profile is developed and the optimum base Ge composition profile function for minimizing the base transit time is also obtained by simulation and analysis. The models of collector depletion-layer transit time, considering the collector current densities and base extension effect, are established. Based on stuctural characteristic of SiGe HBT, the model of collector transit time is established. And these models are simulated and analyzed.4) Model of large signal equivalent circuit of microwave power SiGe HBTThe model of large signal equivalent circuit of SiGe HBT could indicate the influence of micro-structure on electricity characteristic. Based on physical conceptions, microscopic structure, work mechanism, carryers distribution and transport of SiGe HBT, the model of large signal equivalent circuit for SiGe HBT and relevant model parameters are established. The Early effect, the velocity saturation, the base extending effect and the self-heating effect are taken into account in this equivalent circuit model.The model holds the features of definite physical meaning and simple topology. And these models are embedded in the Pspice by its DEVEQ. The model is simulated and analyzed in DC and AC by the Pspice, and the simulation results accord with that of other literatures.5) Optimization of microwave power SiGe HBT structureAccording to design requirement of electrical parameters of S-band 100W SiGe HBT chip, based on the SiGe material physical parameters, the hetero-emitter-junction and the achievable technology of SiGe HBT, the vertical structure parameters are optimized, including the thickness of emitter, base and collector region, the doping concentration, the Ge profiles in the base of SiGe HBT. And the planar structure parameters are optimized, including the length and the width of emitter and base, the space between emitter and base, the ballast resistor of the emitter and the multi-layer metal electrode structure of SiGe HBT. The ratio of the emitter region area and the base region area is optimized.6) Technology design and realization of microwave power SiGe HBTBased on design requirement of frequency and power of microwave power SiGe HBT and specific fabrication technology of strained SiGe material, the process flow of SiGe HBT fabrication is optimized. The estimated models of depth and concentration of ion-implant is established. Based on the geometric structure of SiGe HBT, the technology of ion-implant and short annealing are optimized. Based on the work condition of SiGe HBT, the layer structure of multi-layer metal electrode and achievement process of sputter and electroplating are optimized.The chip of HBT is firstly fabricated in domestic, and the chip is tested, and meets follows:BVEBO=6.5V, BVCBO=75V, BVCEO=35V,β~25.7) Internal matching and power combination of microwave power SiGe HBTThe models of input and output resistance of S-band power SiGe HBT chip are established, and input and output resistance are estimated. The input and output internal matching networks are optimized. The influence of element of internal matching networks on performance of HBT is studied. And the models of inductance introducted by metal leading wire and mutual-inductance between two metal leading wires are established. The reason leading non-uniform distribution of power in power combination is studied, and the estimated model of power deviation is established. And the power combination technology is studied. Based on preview research, the S-band 100W SiGe HBT are firstly developed in domestic, which are tested, and meet follows: Working voltage 30 V Working frequency 2.7GHz—3.1GHz Impulse duyt ratio 1%--5% Input power>100W Power gain≥5dB.更多还原