【作者】 沈珮；

【导师】 张万荣；

【作者基本信息】 北京工业大学 ， 微电子学与固体电子学， 2012， 博士

【摘要】 射频SiGe异质结双极晶体管(Hetrojunction bipolar transistor, HBT)作为新型射频器件，因为具有与III-V族器件可媲美的增益特性和频率特性、与现有的Si工艺可兼容的高集成能力，所以逐渐被运用在超宽带(Ultra-wideband, UWB)低噪声放大器(Low noise amplifier, LNA)设计中。SiGe HBT UWB LNA的2个核心研究内容是器件与电路。优异的器件性能是获得良好电路性能的基础。对器件而言，对影响包括噪声在内的器件性能的工作频率、偏置条件、几何参数、制备工艺等因素的研究一直十分活跃，同时，对器件噪声模型与噪声参数提取方法的研究也备受关注。另一方面，市场对高增益、小面积的UWB LNA的需求，使得不采用电感仍能同时实现优异的噪声特性与阻抗特性、以及获得良好的高频增益与宽带增益平坦度性能的技术研究成为研究热点。本论文围绕着射频SiGe HBT与SiGe HBT UWB LNA开展研究，主要工作有：首先，针对目前在SPICE设计工具中使用的SiGe HBT噪声模型(SPICEnoise model)未考虑射频关联的情况，首次提出了涵括射频关联噪声的新噪声模型。新噪声模型考虑了集电结空间电荷区(Collector-base junction space chargeregion, CB SCR)延迟效应对基极噪声电流源与集电极噪声电流源的影响。新模型采用了广泛使用的HICUM模型的表征形式，并使用Verilog-A编译设计，可以内嵌至任意标准CAD设计工具中，与已存在的晶体管直流、交流和频率等模型相兼容。将新噪声模型与SPICE噪声模型一起与SiGe HBT实测结果进行比较，表明新噪声模型与器件实测结果吻合得更好。其次，本文首次提出了Z参数噪声参量提取法。与传统Y参数提取法相比，新方法显著优点是不需要Y-Z参数转化，直接在器件噪声参量与电路的端口阻抗参量之间建立了联系，更方便同步实现电路噪声匹配与阻抗匹配。第三，从理论和实验上全面研究了频率(f)、集电极电流(IC)和几何参数对射频SiGe HBT最小噪声系数(NFmin)的影响。发现，NFmin随f的增大呈上抛物线增长，通过抛物线切线斜率，给出了优化NFmin的三个关键条件---高电流增益(β)、低基极电阻(RB)和高特征频率(fT)；在一定频率下，存在一个最优IC，使晶体管获得最低NFmin；适度地增大发射极长宽比、减小发射极-基极条间距和增多基极条数，均有益于降低NFmin。第四，改进了同步实现噪声匹配与输入单端阻抗匹配技术，提出了采用L-C与R-L-C复用网络的同步实现噪声匹配与输入输出双端阻抗匹配(Simultaneousnoise and both input and output ports matching, SNBIOM)技术。对比SPICE噪声模型，研究了新噪声模型对C波段射频低噪声放大器噪声匹配、输入共轭阻抗匹配、SNBIOM等设计的影响。研究表明，与SPICE噪声模型相比，新噪声模型使射频低噪声放大器更易于实现噪声匹配、输入共轭阻抗匹配和SNBIOM，其中，当对采用电压偏置、电流偏置的放大器进行SNBIOM设计时，新噪声模型在不影响高增益和高稳定性的条件下，还改善了IIP3，尤其是对采用电流偏置的放大器的IIP3改善更明显。第五，本文首次对采用新型复合反馈电阻、不采用电感的高增益、小面积SiGe HBT超宽带低噪声放大器的设计技术进行了研究。首先，为了实现电路高增益，分析了达林顿对(Darlington pairs, DP)的增益改善技术；其次，为了保障增益的平坦性，比较研究了旁路电感补偿与旁路电容补偿的增益平坦度改善技术，研究发现旁路电容补偿技术更佳；最后，首次提出了新型复合电阻反馈技术，结合DP技术与旁路电容补偿技术，使得不采用电感设计的小面积UWBLNA仍然能够获得良好的SNBIOM、高频增益与增益平坦度。完成的新型SiGe HBT UWB LNA，在3-10GHz内， S21高达24.33dB，增益平坦度为±0.7dB，S11低至-21dB，S22低至-14dB，NF与NFmin非常接近，低于3.7dB，Mul_l恒大于1。由于没有引入螺旋电感，所以电路总体版图尺寸仅为0.18mm2(0.45×0.40mm~2)。最后，立足国内现有工艺和材料生长条件，摸索出了一套适合SiGe HBTUWB LNA单片微波集成电路(Monolithic microwave integrated circuit, MMIC)的制作工艺流程，并对射频SiGe HBT的平面集成工艺流程进行了单步研发实验。单步实验中，成功制备了具有优良直流特性、fT/fMAX=7/6.93GHz、在1.2GHz内NF低至2.5dB、适合做L、S和C波段射频放大器有源器件的SiGeHBT。采用MMIC工艺流程，成功制备了新型复合电阻反馈的SiGe HBT UWBLNA MMIC，为了对比，同时也制备了单一电阻反馈的SiGe HBT DP LNAMMIC。因为没有采用占片面积大的螺旋电感，所以芯片面积仅为0.2mm2(0.5×0.4mm~2)。初步在片测试结果显示，两款LNA MMICs中，新型复合电阻反馈的UWB LNA MMIC的增益更高，噪声系数更低，阻抗匹配更佳，0.2-1.2GHz内，GA高达24.7dB，NF低至2.8dB；0.5-3.5GHz内，S21高达25.5dB，S11和S22均低于-10dB。更多还原

【Abstract】 As a novel Radio Frequency(RF) devices, SiGe heterojunction bipolar transistor(HBT) are gradually used in design of ultra-wideband low noise amplifier(UWB LNA)due to comparable gain and frequency characteristics to the III-V devices, and highintegration with existing silicon technology. Two critical research aspects of SiGeHBT UWB LNA are device and circuit. As well known, good device performance isfundamental to achieve good performance of circuit. In one hand, the investigation offactors which affect device performances never stop including operating frequency,bias condition, geometry parameters, fabrication technology and so on. Meanwhile,researchers are also pay great attention to noise model of device and extractionmethodology of noise parameters. In another hand, the market requirements for smalldie area and high gain of UWB LNA push the improvement techniques researches toachieve simultaneously excellent noise and impedance characteristics withoutinductor, to offer the high gain with good gain flatness in wide frequency band.In this dissertation, researches are focus on SiGe HBT and SiGe HBT UWB LNA,the main works can be summarized as follows:Firstly, in order to solve the problem that noise model of SiGe HBT used in SPICEdesign tool at present ignores the RF correlation, the novel noise model consideringRF correlated noise is developed. In the novel noise model, the impact of collector-base junction space charge region(CB SCR) delay effect on base noise current sourceand collector current source is taken into account. And the novel model is representedby popular HICUM model, as well as be compiled using Verilog-A(the wholecompiling program is given in appendix A). Therefore, the novel noise model couldbe embed into any standard CAD design tools, and compatible with other existingmodels, such as DC model, AC model, frequency model and so on. The novel noisemodel and SPICE noise model are compared with measured results of SiGe HBTs.The results show that the noise parameters extracted from the novel noise modelagrees well with device measurement.Secondly, Z parameters extraction methodology of transistor noise parameters isproposed for the first time. New methodology directly builds the relationship betweennoise parameters of devices and port impedance parameters of circuits without Y-Zconversion process, which is clearly an attractive benefit compared with traditional Yparameters extraction methodology. It is much more convenient to achieve thesimultaneous noise and impedance matching of LNA.Thirdly, the impact of frequency(f), collector current(IC) and geometry parameterson the minimum noise figure(NFmin) of RF SiGe HBT are examined theoretically and experimentally. It is showed that NFmingrows up parabolically with increase offrequency. Hence, three critical conditions of high current gain(β), low baseresistor(RB) and high cut-off frequency(fT) to optimize NFminare given by analyzingthe tangent slope of the parabola curve. Furthermore, there exists an optimum ICatwhich transistor achieves the minimum NFminfor a given operating frequency. Inaddition, it is beneficial for reducing the NFminby slightly increasing the ratio ofemitter length to emitter width, gently reducing spacing between emitter stripe andbase stripe, and slimly adding base stripes.Fourthly, the technique relating to achieve simultaneous noise and both input andoutput ports impedance matching(SNBIOM) is proposed by adopting compositenetwork of L-C and R-L-C based on improved technique of simultaneous noise andsingle input port impedance matching. Then the impacts of the novel noise model onC waveband RF LNA designs are comprehensively investigated, which includedesigns of noise matching, input conjugate impedance matching and SNBIOM. It isfound that the novel noise model is more attractive to easily achieve noise matching,impedance matching, and SNBIOM compared with traditional SPICE noise model.Furthermore, the noise model even gives rise to IIP3improvement for SNBIOMdesign of LNAs with voltage bias and current bias without negative effects on highgain and high stability. Especially, the improvement is more dramatical for the LNAwith current bias.Fifthly, the design techniques for SiGe HBT UWB LNA to achieve high gain andsmall die area are investigated by taking advantage of the novel composite feedbackresistive without using inductor. First of all, the improved technique of Darlingtonpairs(DP) is analyzed to achieve high gain. Then, in order to guarantee flatness of gain,the technique for gain flatness enhancement is investigated by comparison betweenbypass inductor and capacitor compensation techniques. It is found that bypasscapacitor compensation technique is better. Finally, for the first time, the novelcomposite resistive feedback technique is proposed in conjunction with DP techniqueand bypass capacitor compensation technique so as to obtain excellent performanceincluding SNBIOM, high gain and high gain flatness, and small die area without usinginductor. This novel SiGe HBT UWB LNA shows that S21is as high as24.33dB withgain flatness of±0.7dB, S11is as low as-21dB, S22is less than-14dB, NF is highlyclose to NFmin, which as low as3.7dB, and Mul_l keeps always larger than1in theband from3GHz to10GHz. Due to absence of spiral inductors, the die area of theSiGe HBT UWB LNA is only0.18mm2(0.45×0.40mm2).Finally, the fabrication processes suitable for SiGe HBT monolithic microwaveintegrated circuit (MMIC) are developed based on the state of the art integrated circuittechnology. Meanwhile, the plane fabrication processes of RF SiGe HBTs for MMICapplication are examined individually, and a series of transistors are fabricated successfully. Due to good DC performance, fT/fmax=7/6.93GHz, NF as low as2.5dBwithin1.2GHz, the fabricated devices are suitable as active devices of L, S, and Cwaveband RF LNA.By adopting developed MMIC processes, SiGe HBT UWB LNA MMIC with thenovel composite resistive feedback is fabricated. Meanwhile, SiGe HBT DP LNAMMIC with single resistive feedback is also fabricated as a counterpart circuit. Theabsence of inductor leads to a small chip area of0.2mm2(0.5×0.4mm2). Initialmeasured results show that, compared with SiGe HBT DP LNA MMIC, SiGe HBTUWB LNA MMIC achieves higher gain, lower NF and better impedance matching,GAas high as24.7dB, NF as low as2.8dB in the band from0.2GHz to1.2GHz, aswell as S21is up to25.5dB, and both S11and S22are lower than-10dB in the band from0.5GHz to3.5GHz.更多还原