Theoretical small-signal performance of Si/SiGe/Si HBT

Application of the Monte Carlo technique to analyze electron and hole transport in bulk Si_0.8Ge_0.2 and strained Si _0.8Ge_0.2/Si is discussed. The computed minority- and majority-carrier transport properties were used in a comprehensive small-signal model to evaluate the high-frequency performance of a state-of-the-art n-p-n heterostructure bipolar transistors (HBT) fabricated with SiGe as the base material. The valence band discontinuity of a SiGe-base HBT reverses the degradation in emitter injection efficiency caused by bandgap narrowing in the base, and permits a higher ratio of base doping to emitter doping than would be practical for a bipolar transistor. Any degradative effect of increased base doping on electron and hole mobilities is offset by improved transport in the strained SiGe base, resulting in a marked decrease in the base resistance and base transit time. Compared to the Si BJT, the use of Si_0.8Ge_0.2 for the base region of an HBT leads to significant improvements in low-frequency common emitter current gain, low-frequency unilateral power gain, and maximum oscillation frequency     

射频Si/SiGe/Si HBT的研究

在Si／SiGe／SiHBT与Si工艺兼容的研究基础上，对射频Si／SiGe／SiHBT的射频特性和制备工艺进行了研究，分析了与器件结构有关的关键参数寄生电容和寄生电阻与Si／SiGe/Si HBT的特征频率fT和最高振荡频率fmax的关系，成功地制备了fT为2．5CHz、fmax为2．3GHz的射频Si／SiGe／SiHBT，为具有更好的射频性能的Si／SiGe／Si HBT的研究建立了基础。     

与Si 工艺兼容的Si/ SiGe/ Si HBT 研究

我们对Si/SiGe/Si HBT及其Si兼容工艺进行了研究,在研究了一些关键的单项工艺的基础上,提出了五个高速Si/SiGe/Si HBT结构和一个低噪声Si/SiGe/Si HBT结构,并已研制成功台面结构Si/SiGe/Si HBT和低噪声Si/SiGe/Si HBT,为进一步高指标的Si/SiGe/Si HBT的研究建立了基础。     

Determination of boron concentration in heavily doped p-type Si1−xGex/Si heterostructure by infrared ellipsometric spectroscopy

Si_1−xGe_x/Si heterostructures play a primary role in the Si-based fast electronics developments of today. In this work, we will present the experimental results of infrared spectroscopic ellipsometry (IRSE) for structural determination of the boron heavily doped SiGe/Si sample grown by ultra-high vacuum chemical vapor deposition (UHVCVD) (the Ge atomic percent, the thickness of SiGe film and boron concentration). Especially, the principle of boron concentration in p-type SiGe film layer determined by IRSE was elucidated in detail. In addition, in order to corroborate the validity of IRSE for determining dopant concentration, secondary ion mass spectroscopy (SIMS) experiment has also been carried out. The close experimental agreement between IRSE and SIMS demonstrate that IRSE as a contactless, and non-destructive technology can be used in-line tools in production used for measuring the Ge content, the thickness of SiGe layer and boron concentration in p-type dopant SiGe/Si heterostructure, which often used the base layer of SiGe hetero-junction bipolar transistor (HBT) devices.     

SiGe/Si HBT高频噪声特性研究

基于器件Y参数,对Si/Si1-xGexHBT的高频噪声进行了模拟。Si/Si1-xGexHBT的高频最小噪声系数随Ge组份x的增加而减小。与Si BJT相比,Si/SiGe HBT具有优异的高频噪声特性。     

GSMBE生长SiGe/Si材料的原位掺杂控制技术

在特定温控下对掺杂气体分子的状态和活性进行控制 ,建立了一套具有自主知识产权的气源分子束外延工艺生长 Si Ge/Si材料的原位掺杂控制技术。采用该技术生长的 Si Ge/Si HBT外延材料 ,可将硼杂质较好地限制在 Si Ge合金基区内 ,并能有效地提高磷烷对 N型掺杂的浓度和外延硅层的生长速率 ,获得了理想 N、P型杂质分布的 Si Ge/Si HBT外延材料     

Si/ SiGe/ Si HBT 的直流特性和低频噪声

在对Si/SiGe/Si HBT及其Si兼容工艺的研究基础上，研制成功低噪声Si/SiGe/Si HBT，测试和分析了它的直流特性和低频噪声特性，为具有更好的低噪声性能的Si/SiGe/Si HBT的研究建立了基础。     

SiGe/SiHBT异质界面与pn结界面的相对位移的影响

从模拟和实验两方面研究了SiGe/Si HBT发射结中pn结界面和SiGe/Si界面的相对位置对器件的电流增益和频率特性的影响.发现两界面偏离时器件性能会变差.尤其是当pn结位于SiGe/Si界面之前仅几十?就足以产生相当高的电子寄生势垒,严重恶化器件的性能.据此分析了基区B杂质的偏析和外扩对器件的影响以及SiGe/Si隔离层的作用.     

SiGe/SiHBT发射结的寄生势垒及其对器件室温和低温特性的影响

研究了SiGe/Si HBT基区B杂质的偏析和外扩散对器件的影响.发现用MBE生长的Si Ge基区中,在材料生长时 B杂质的上述行为会严重破坏器件的室温电流增益并改变器件的低温性能.采用数值计算分析了B杂质的上述行为与在发射结产生的寄生势垒的关系,解释了器件温度特性的实验结果.并根据计算模拟和实验,讨论了SiGe隔离层的作用和优化的厚度     

THE EFFECT OF DOPANT OUTDIFFUSION ON THE NEUTRAL BASE RECOMBINATION CURRENT IN Si/SiGe/Si HETEROJUNCTION BIPOLAR TRANSISTORS

A new analytical model for the base current of Si/SiGe/Si heterojunction bipolar transistors(HBTs) has been developed. This model includes the hole injection current from the base to the emitter, and the recombination components in the space charge region(SCR) and the neutral base. Distinctly different from other models, this model includes the following effects on each base current component by using the boundary condition of the excess minority carrier concentration at SCR boundaries: the first is the effect of the parasitic potential barrier which is formed at the Si/SiGe collector-base heterojunction due to the dopant outdlffusion from the SiGe base to the adjacent Si collector, and the second is the Ge composition grading effect. The effectiveness of this model is confirmed by comparing the calculated result with the measured plot of the base current vs. the collector-base bias voltage for the ungraded HBT. The decreasing base current with the increasing the collector-base reverse bias voltage is successfully explained by this model without assuming the short-lifetime region close to the SiGe/Si collector-base junction, where a complete absence of dislocations is confirmed by transmission electron microscopy (TEM)[1]. The recombination component in the neutral base region is shown to dominate other components even for HBTs with a thin base, due to the increased carrier storage in the vicinity of the parasitic potential barrier at collector-base heterojunction.     

采用高真空 /快速热处理 /化学气相淀积外延SiGe HBT结构

采用新近研制的高真空 /快速热处理 /化学气相淀积 (HV/ RTP/ CVD)系统生长了应变 Si Ge材料 .通过仔细设计的处理过程可以得到器件质量的材料 .Ge组分可以变化至 0 .2 5 ,可以得到控制良好的 n型和 p型掺杂层 ,适用于异质结双极型晶体管 (HBT)的制作 .研究了 Si Ge HBT的 n- Si/ i- p+ - i Si Ge/ n- Si结构 .所制作出的微波 HBT性能良好 ,证明了设备和工艺的水平     

16 Gbit/s multiplexer IC using double mesa Si/SiGe heterojunction bipolar transistors

A double mesa Si/SiGe heterojunction bipolar transistor (HBT) was developed for application in integrated circuits. The HBT is characterised by an emitter base heterojunction and consequently by a high base doping concentration. By using these transistors an integrated digital circuit, a multiplexer, was implemented. The measured bit rate of this first Si/SiGe HBT circuit was 16 Gbit/s.<>     

Applications and processing of SiGe and SiGe:C for high-speed HBT devices

The continued growth of high-speed-digital data transmission and wireless communications technology has motivated increased integration levels for ICs serving these markets. Further, the increasing use of portable wireless communications tools requiring long battery lifetimes necessitates low power consumption by the semiconductor devices within these tools. The SiGe and SiGe:C materials systems provide solutions to both of these market needs in that they are fully monolithically integratible with Si BiCMOS technology. Also, the use of SiGe or SiGe:C HBTs for the high-frequency bipolar elements in the BiCMOS circuits results in greatly decreased power consumption when compared to Si BJT devices.Either a DFT (graded Ge content across the base) or a true HBT (constant Ge content across the base) bipolar transistor can be fabricated using SiGe or SiGe:C. Historically, the graded profile has been favored in the industry since the average Ge content in the pseudomorphic base is less than that of a true HBT and, therefore, the DFT is tolerant of higher thermal budget processing after deposition of the base. The inclusion of small amounts of C (e.g. <0.5%) in SiGe is effective in suppressing the diffusion of B such that very narrow extremely heavily doped base regions can be built. Thus the f_T and f_max of a SiGe:C HBT/DFT are capable of being much higher than that of a SiGe HBT/DFT.The growth of the base region can be accomplished by either nonselective mixed deposition or by selective epitaxy. The nonselective process has the advantage of reduced complexity, higher deposition rate and, therefore, higher productivity than the selective epitaxy process. The selective epi process, however, requires fewer changes to an existing fabrication sequence in order to accommodate SiGe or SiGe:C HBT/DFT devices into the BiCMOS circuit.     

Growth of SiGe Films by Cold-wall UHV/CVD Using GeH4 and Si2H6

An ultrahigh vacuum chemical vapor deposition (UHV/CVD) system is introduced.SiGe alloys and SiGe/Si multiple quantum wells (MQWs) have been grown by cold-wall UHV/CVD using disilane(Si2H6) and germane (GeH4) as the reactant gases on Si(100) substrates.The growth rate and Ge contents in SiGe alloys are studied at different temperature and different gas flow.The growth rate of SiGe alloy is decreased with the increase of GeH4 flow at high temperature.X-ray diffraction measurement shows that SiGe/Si MQWs have good crystallinity,sharp interface and uniformity.No dislocation is found in the observation of transmission electron microscopy(TEM) of SiGe/Si MQWs.The average deviation of the thickness and the fraction of Ge in single SiGe alloy sample are 3.31% and 2.01%, respectively.     

77K下电流增益为2.6万的SiGe/Si HBT

通过优化设计SiGe/SiHBT的纵向参数,找到一种低温工艺方法,研制出了在液氮温度下电流增益达到26000的高增益异质结晶体管。     

A 30-Gbit/s demultiplexer IC based on Si/SiGe emitter baseheterojunction bipolar transistors

A 30-Gbit/s demultiplexer IC has been fabricated and tested using an improved double mesa Si/SiGe heterojunction bipolar transistor process. This is-to our knowledge-the highest ever reported bit rate for “real” (as opposed to drift transistor) Si/SiGe HBT circuits. The result was mainly reached by scaling down the transistor sizes to reduce parasitics. The minimum emitter mesa width was 1 μm     

Measurement of collector-base junction avalanche multiplicationeffects in advanced UHV/CVD SiGe HBT's

This paper presents measurements of the avalanche multiplication factor (M-1) in SiGe HBTs using a new technique capable of separating the avalanche multiplication and Early effect contributions to the increase of collector current with collector-base bias, as well as allowing safe measurements at practical current densities. The impact of collector doping, current density, Ge profile, and operation temperature are reported for the first time using measured and simulated results from a production quality UHV/CVD SiGe HBT technology. Limitations of the technique in the presence of significant self-heating are discussed. By turning on the secondary hole impact ionization, we revealed the difference in impact ionization between strained SiGe and Si in the presence of the “dead space” effect. Despite its smaller bandgap, the compressively strained SiGe layer shows an apparent decrease in the secondary hole impact ionization rate compared to Si     

Si/SiGe PMOS器件的模拟优化设计与样品研制

通过理论分析与计算机模拟,给出了以提高跨导为目标的Si/SiGe PMOSFET优化设计方法,包括栅材料的选择、沟道层中Ge组分及其分布曲线的确定、栅氧化层及Si盖帽层厚度的优化和阈值电压的调节,基于此已研制出Si/SiGe PMOSFET器件样品.测试结果表明,当沟道长度为2μm时,Si/SiGe PMOS器件的跨导为45mS/mm(300K)和92mS/mm(77K),而相同结构的全硅器件跨导则为33mS/mm(300K)和39mS/mm(77K).     

Si/GexSi1-x heterojunction bipolartransistors with the GexSi1-x base formed by Geion implantation in Si

We have fabricated n-p-n, Si/Ge₂Si_1-x heterojunction bipolar transistors (HBTs) with the Ge_xSi_1-x base formed by high-dose Ge implantation followed by solid phase epitaxy. The fabrication technology is a standard self-aligned, double polysilicon process scheme for Si with the addition of the high-dose Ge implantation. The transistors are characterized by a 60 mn-wide neutral base with a Ge concentration peak of ≈8 at.% at the base-collector junction. The HBTs show good electrical characteristics and compared to Si homojunction transistors show lower base resistance, larger values of current gain, and a lower emitter-to-collector transit time     

Simulation analysis of the DC current gain in an n-p-n a-Si:H/SiGe/Si heterojunction bipolar transistor

This paper presents the results of a simulation study focused on the evaluation of the DC characteristics of an n-p-n SiGe-based heterojunction bipolar transistor (HBT) performing an extremely thin n⁺ hydrogenated amorphous silicon (a-Si:H) emitter. The a-Si:H(n)/SiGe(p) structure exhibits an energy gap difference of approximately 0.8 eV mostly located at the valence band side and this results in an optimal configuration for the emitter/base junction to improve the emitter injection efficiency and thus the device performance.Considering a 20% Ge uniform concentration profile in the base region, simulations indicate that the DC characteristics of an a-Si:H/SiGe HBT are strictly dependent on two essential geometrical parameters, namely the emitter width and the base width. In particular, the emitter thickness degrades device characteristics in terms of current handling capabilities whereas higher current gains are obtained for progressively thinner base regions. A DC current gain exceeding 9000 can be predicted for an optimized device with a thin emitter and a 10 nm-thick, doped base.