Determination of bandgap narrowing and parasitic energy barriers inSiGe HBT's integrated in a bipolar technology

This paper describes a method for characterizing the bandgap narrowing and parasitic energy barrier in SiGe heterojunction bipolar transistors (HBTs), fabricated using a single-polysilicon self-aligned bipolar process. From a comprehensive study of the temperature dependence of the collector current, the bandgap narrowing in the base due to germanium has been dissociated from that due to the heavy dopant concentration. The same approach has been used to characterize the height and width of parasitic energy barriers which appear when boron out-diffusion from the SiGe base is present. The method has been applied to SiGe heterojunction bipolar transistors fabricated using a single polysilicon, self-aligned, bipolar process, as well as mesa transistors. The experimental results show that small geometry transistors have degraded collector currents due to boron out-diffusion around the perimeter of the emitter. This behavior has been explained by accelerated boron diffusion due to point defects generated during the extrinsic base implant. The values of undoped SiGe spacer thickness needed to suppress the parasitic energy barrier are described. Finally, high-frequency results are reported, which correlate the frequency transition to these parasitic energy barriers     

Si:SiGe MODFET current mirror

Measurements of the DC characteristics of a negative inverting, voltage-following current mirror are presented. The circuit design uses prototype n-depletion mode, modulation doped field effect transistors employing Si:SiGe heterojunction technology and is based on recently established circuit design techniques for GaAs MESFET technology. The results show a quasi-linear response with gate voltage swings (V_gs ) of ±0.5 V. Increases in the achievable range of V_gs are anticipated through changes in material growth and device processing, and also through enhancement of the circuit design     

A 5-GHZ Low-Power Series-Coupled BiCMOS Quadrature VCO With Wide Tuning Range

This letter presents a novel quadrature voltage controlled oscillator (QVCO) implemented in a 47-GHz SiGe BiCMOS technology. The QVCO is a serially coupled LC VCO that utilizes SiGe heterojunction bipolar transistors for oscillation and metal oxide semiconductor field effect transistors for coupling. The SiGe BiCMOS QVCO prototype achieves about 14.6% tuning range from 4.3 to 5GHz. The phase noise of the QVCO is measured as -114.3 dBc/Hz at 2-MHz offset. The 5-GHz QVCO core consumes 6-mA current from a 3.3-V power supply and occupies 0.88mm² area     

Product applications and technology directions with SiGe BiCMOS

In this paper, we highlight the effectiveness and flexibility of SiGe BiCMOS as a technology platform over a wide range of performance and applications. The bandgap-engineered SiGe heterojunction bipolar transistors (HBTs) continue to be the workhorse of the technology, while the CMOS offering is fully foundry compatible for maximizing IP sharing. Process customization is done to provide high-quality passives, which greatly enables fully integrated single-chip solutions. Product examples include 40-Gb/s (OC768) components using high-speed SiGe HBTs, power amplifiers compatible for cellular applications, integrated voltage-controlled oscillators, and very high-level mixed-signal integration. It is argued that such key enablements along with the lower cost and higher yields attainable by SiGe BiCMOS technologies will provide competitive solutions for the communication marketplace.     

Characterization of the effectiveness of carbon incorporation inSiGe for the elimination of parasitic energy barriers in SiGe HBTs

An electrical method is applied to SiGe and SiGe:C heterojunction bipolar transistors (HBTs) to extract the bandgap narrowing in the base layer and to characterize the presence of parasitic energy barriers in the conduction band, arising from boron transient enhanced out-diffusion from the SiGe layer. It is shown that a background carbon concentration within the base (≈10²⁰ cm^-3) eliminates parasitic energy barriers at the collector/base junction, and hence shows that transient enhanced diffusion of boron from the base has been completely suppressed     

High-speed source-heterojunction-MOS-transistor (SHOT) utilizing high-velocity electron injection

We have developed the source-heterojunction-MOS-transistor (SHOT), a novel high-speed MOSFET with relaxed-SiGe/strained-Si heterojunction source structures for quasi-ballistic or full-ballistic transistors. Using the band-offset energy at the source SiGe/strained-Si heterojunction, high velocity electrons can be injected into the strained-Si channel from the SiGe source region. For the first time, we have experimentally demonstrated that the transconductance is enhanced in SHOT for high applied drain voltage, compared to that of strained- and conventional silicon-on-insulator MOSFETs. We have also shown that the transconductance enhancement in SHOT depends on both the gate drive and the drain bias.     

SiGe HBT的速度优化设计

从理论分析角度介绍了优化SiGe异质结晶体管速度的方法。结合双极晶体管的工艺限制，介绍了SiGeHBT的基本原理，讨论了SiGeHBT的发射区／基区／集电区设计。最后，以一个100GHzfmax和fT的HBT为例，对电路制作工艺参数进行了讨论。     

On the profile design and optimization of epitaxial Si- andSiGe-base bipolar technology for 77 K applications. I. Transistor DCdesign considerations

The DC design considerations associated with optimizing epitaxial Si- and SiGe-base bipolar transistors for the 77-K environment are examined in detail. Transistors and circuits were fabricated using four different vertical profiles, three with a graded-bandgap SiGe base, and one with a Si base for comparison. All four epitaxial-base profiles yield transistors with DC properties suitable for high-speed logic applications in the 77-K environment. The differences between the low-temperature DC characteristics of Si and SiGe transistors are highlighted both theoretically and experimentally. A performance tradeoff associated with the use of an intrinsic spacer layer to reduce parasitic leakage at low temperatures and the consequent base resistance degradation due to enhanced carrier freeze-out is identified. Evidence that a collector-base heterojunction barrier effect severely degrades the current drive and transconductance of SiGe-base transistors operating at low temperatures is provided     

An electrical method for measuring the difference bandgap acrossthe neutral base in SiGe HBT's

This paper describes an electrical method for measuring the bandgap difference across the neutral base of SiGe heterojunction bipolar transistors (HBT's). It measures the effective bandgap difference due to differences in germanium concentration including the effects of heavy doping on bandgap reduction. Numerical device simulation was used to investigate the use of the proposed technique on high performance transistors with graded and uniform germanium profiles. Experimental verification of the technique is conducted on SiGe HBT devices fabricated using LPCVD     

SiGe材料及其在双极型器件中的应用

SiGe材料具有很多独特的性质,高性能的应变SiGe外延层能够将能带工程的概念引入到传统的S基材料中去。外延SiGe合金使得在Si基材料上制作性能优异的双极晶体管成为可能。本文回顾了siGe材料和SiGe异质结双极晶体管的最新研究进展,包括它们的结构、性能、制作工艺、优点以及未来发展方向等。     

Design of 20 GHz high performance LC-VCOs in a 52 GHz fT SiGe:C BiCMOS technology

The design and analysis of fully integrated 20 GHz voltage controlled oscillators (VCOs) for low cost and low power communication system are presented in this paper. Two differential topographies have been studied: balanced Colpitts VCO and LC-VCO using a cross-coupled differential pair. We have focused on oscillation frequency, tuning range, phase noise, output power optimization and buffer stage specifications. SiGe:C hetero-junction bipolar transistors of a 52 GHz cut-off frequency have been used and produced via a monolithic BiCMOS technology.     

Voltage stress-induced hot carrier effects on SiGe HBT VCO

This paper presents the hot carrier (HC) induced performance degradation in a 10 GHz voltage controlled oscillator (VCO) with SiGe heterojunction bipolar transistors (HBTs). SiGe device characteristics due to HC stress are examined experimentally. The vertical bipolar inter-company (VBIC) model parameters extracted from measured data are used in Cadence SpectreRF simulation to verify the HC effect on the VCO. The VCO shows significant vulnerability to hot carriers.     

Integrated enhancement- and depletion-mode FET's inmodulation-doped Si/SiGe heterostructures

We present results of enhancement and depletion mode transistors fabricated on the same layer structure of Si/SiGe, without using gate recess. The current in the enhancement mode device is controlled by a p-n junction, while that of the depletion-mode device is controlled by a Schottky barrier. A peak transconductance of 327 mS/mm and 417 mS/mm has been achieved in 0.5-μm gate length depletion and enhancement-mode transistors, respectively     

Microwave and noise performance of SiGe BiCMOS HBT under cryogenic temperatures

In this letter, the microwave and noise performance of SiGe heterojunction bipolar transistors (HBTs) has been characterized when cooling down the temperature. It was found that SiGe HBTs (fabricated in the framework of BiCMOS process) exhibit a maximum oscillation frequency f/sub max/ of about 292 GHz at 78 K, which represents an increase of about 30% with the value measured at room temperature. The noise performance has also been characterized at cryogenic temperatures, using an original de-embedding approach. Then, using the Hawkin's noise model in conjunction with an accurate small signal equivalent extraction, the four noise parameters have been estimated. The noise figure with a 50 /spl Omega/ source impedance was measured to be equal to 1.5 dB at 40 GHz at 78 K, which is one of the lowest value reported for BiCMOS SiGe HBT in the millimeter-wave range.     

SiGe-channel heterojunction p-MOSFET's

The advances in the growth of pseudomorphic silicon-germanium epitaxial layers combined with the strong need for high-speed complementary circuits have led to increased interest in silicon-based heterojunction field-effect transistors. Metal-oxide-semiconductor field-effect transistors (MOSFET's) with SiGe channels are guided by different design rules than state-of-the-art silicon MOSFET's. The selection of the transistor gate material, the optimization of the silicon-germanium channel profile, the method of threshold voltage adjustment, and the silicon-cap and gate-oxide thickness sensitivities are the critical design parameters for the p-channel SiGe MOSFET. Two-dimensional numerical modeling demonstrates that n⁺ polysilicon-gate SiGe p-MOSFET's have acceptable short-channel behavior at 0.20 μm channel lengths and are preferable to p⁺ polysilicon-gate p-MOSFET's for 2.5 V operation. Experimental results of n⁺-gate modulation-doped SiGe p-MOSFET's illustrate the importance of the optimization of the SiGe-channel profile. When a graded SiGe channel is used, hole mobilities as high as 220 cm² /V.s at 300 K and 980 cm²/V.s at 82 K are obtained     

The influence of Ge grading on the bias and temperaturecharacteristics of SiGe HBTs for precision analog circuits

This paper analyzes the effects of Ge profile shape on the bias and temperature characteristics of advanced UHV/CVD SiGe heterojunction bipolar transistors (HBTs). The widely used bandgap reference (BGR) design equation and a more general analytical expression incorporating Ge grading developed in this work are used to compare silicon devices to their SiGe counterparts. Theory, device measurements, and SPICE simulations are used to investigate the impact of Ge grading on SiGe HBT precision voltage references. It is concluded that conventional SPICE can be used to account for Ge grading effects in SiGe HBT modeling. Sufficient Ge grading can have a significant impact on the accuracy of precision voltage references, particularly at reduced temperatures, and thus warrants attention     

A 0.2-μm 180-GHz-fmax 6.7-ps-ECL SOI/HRS self-alignedSEG SiGe HBT/CMOS technology for microwave and high-speed digitalapplications

A technology for combining 0.2-μm self-aligned selective-epitaxial-growth (SEG) SiGe heterojunction bipolar transistors (HBTs) with CMOS transistors and high-quality passive elements has been developed for use in microwave wireless and optical communication systems. The technology has been applied to fabricate devices on a 200-mm SOI wafer based on a high-resistivity substrate (SOI/HRS). The fabrication process is almost completely compatible with the existing 0.2-μm bipolar-CMOS process because of the essential similarity of the two processes. SiGe HBTs with shallow-trench isolations (STIs) and deep-trench isolations (DTIs) and Ti-salicide electrodes exhibited high-frequency and high-speed capabilities with an f_max of 180 GHz and an ECL-gate delay of 6.7 ps, along with good controllability and reliability and high yield. A high-breakdown-voltage HBT that could produce large output swings for the interface circuit was successfully added. CMOS devices (with gate lengths of 0.25 μm for nMOS and 0.3 μm for pMOS) exhibited excellent subthreshold slopes. Poly-Si resistors with a quasi-layer-by-layer structure had a low temperature coefficient. Varactors were constructed from the collector-base junctions of the SiGe HBTs. MIM capacitors were formed between the first and second metal layers by using plasma SiO₂ as an insulator. High-Q octagonal spiral inductors were fabricated by using a 3-μm thick fourth metal layer     

Strained layer heterostructures, and their applications to MODFETs,HBTs, and lasers

Recent developments in strained layer epitaxial systems are reviewed. Their interest stems primarily from the additional degree of freedom that strained layers provide in the design of heterostructures and devices, which has led to device structures that can be tailored to a particular application with, in many cases, performances that are and out of reach with lattice-matched systems alone. With the advent of SiGe alloys, the concept of strained layers was extended to include the elemental semiconductors as well. Si/SiGe heterojunctions have provided a way to study quantum phenomena and explore heterojunction bipolar transistors (HBTs) and field-effect transistors (FETs). In optoelectronics, quantum well lasers with strained InGaAs active layers provide considerable reduced threshold current density. With coherently strained active layers based on GaAs, lasers with longevities superior to those with lattice-matched channels have been obtained     

微波大功率SiGe HBT的研究进展及其应用

文章论述了SiGe异质结双极晶体管(HBT)在微波功率领域应用的优势,详细介绍了微波功率SiGe HBT的结构设计方法,以及主要影响器件性能的材料和结构因素,评述了其最新进展及今后发展方向.     

Simulation of SiGe:C HBTs using neural network and adaptive neuro-fuzzy inference system for RF applications

In this article, the small-signal equivalent circuit model of SiGe:C heterojunction bipolar transistors (HBTs) has directly been extracted from S-parameter data. Moreover, in this article, we present a new modelling approach using ANFIS (adaptive neuro-fuzzy inference system), which in general has a high degree of accuracy, simplicity and novelty (independent approach). Then measured and model-calculated data show an excellent agreement with less than 1.68?×?10^?5% discrepancy in the frequency range of higher than 300 GHz over a wide range of bias points in ANFIS. The results show ANFIS model is better than ANN (artificial neural network) for redeveloping the model and increasing the input parameters.