Silicon-germanium Heterojunction Bipolar Transistors Research Articles

Sensitivity investigation of 100-MeV proton irradiation to SiGe HBT single event effect

The single event effect (SEE) sensitivity of silicon–germanium heterojunction bipolar transistor (SiGe HBT) irradiated by 100-MeV proton is investigated. The simulation results indicate that the most sensitive position of the SiGe HBT device is the emitter center, where the protons pass through the larger collector-substrate (CS) junction. Furthermore, in this work the experimental studies are also carried out by using 100-MeV proton. In order to consider the influence of temperature on SEE, both simulation and experiment are conducted at a temperature of 93 K. At a cryogenic temperature, the carrier mobility increases, which leads to higher transient current peaks, but the duration of the current decreases significantly. Notably, at the same proton flux, there is only one single event transient (SET) that occurs at 93 K. Thus, the radiation hard ability of the device increases at cryogenic temperatures. The simulation results are found to be qualitatively consistent with the experimental results of 100-MeV protons. To further evaluate the tolerance of the device, the influence of proton on SiGe HBT after gamma-ray (60Coγ) irradiation is investigated. As a result, as the cumulative dose increases, the introduction of traps results in a significant reduction in both the peak value and duration of the transient currents.

The effect of electrical stress and thermal annealing on swift heavy ion irradiated SiGe HBTs

The nano-engineered silicon–germanium heterojunction bipolar transistors (SiGe HBTs) were irradiated with 100 MeV phosphorous ions up to a high total dose of 100 Mrad. The irradiated SiGe HBTs were subjected to mixed mode (MM) electrical stress and isochronal annealing. The DC electrical characteristics were studied for ion irradiated, electrically stressed and thermally annealed SiGe HBTs. The important parameters such as base current (IB), current gain (hFE) and output characteristics of the irradiated SiGe HBTs were significantly degraded after 100 Mrad of the total dose. This is due to high energy ion induced damages in Emitter-Base (E-B) and Shallow Trench Isolation (STI) oxides. A significant recovery in device parameters was observed after both MM stress and isochronal annealing. The recovery in electrical characteristics of the irradiated SiGe HBTs is mainly due to the raise in the junction temperature and de-trapping of trapped charges.

Neuroevolution-Based Network Architecture Evolution in Semiconductor Manufacturing.

Promoted model architectures or algorithms are crucial for intelligent manufacturing since developing them takes a lot of trial and error to embed the domain knowledge into the models correctly. Especially in semiconductor manufacturing, the whole processes depend on complicated physical equations and sophisticated fine-tuning. Therefore, we use a neuroevolution-based model to search the optimized architecture automatically. The collector current value at a particular bias of the silicon-germanium (SiGe) heterojunction bipolar transistor, generated by technology computer-aided design (TCAD), is used as the target dataset with six process parameters as the inputs. The processes include oxidation, dry and wet etching, implantation, annealing, diffusion, and chemical-mechanical polishing. Our work can build a suitable model network with a fast turnaround time, and practical physical constraints are fused in it without domain knowledge extraction. Take the case with 3840 data and one output as an instance. The mean square errors of the train set and validation set, as well as the mean absolute percentage error of the test set, are 1.317 × 10-6, 7.215 × 10-7, and 0.216 while using multilayer perceptron (MLP) and they are 3.285 × 10-7, 1.661 × 10-7, and 0.097 while using NE. The consequences show that the work in this vein is promising. According to the trend plot and results, the ability to extract physic is much better than the traditional (MLP) model.

Reliability studies on bipolar transistors under different particles radiation

The reliability of silicon bipolar junction transistors (Si BJTs) and silicon germanium heterojunction bipolar transistors (SiGe HBTs) were studied under 80 MeV nitrogen (N6+) ions and 60Co gamma radiation in a total dose from 1 to 100Mrad at 300 K. Different DC electrical parameters namely Gummel Characteristics (IB, IC–VBE), excess base current (ΔIB), current gain (hFE), and output characteristics (IC–VCE) were studied before as well as after being subjected to radiations. Both radiations caused substantial degradation in parameters such as an increase in IB, a decrease in the hFE, and a decrease in ICsat. The parametric degradation is more in Si BJT (99% degradation in hFE after ion irradiation) when compared to SiGe HBT (45% degradation in hFE). The SRIM/TRIM simulations were employed to analyze the energy loss phenomenon and ion range in device structures. Annealing studies were also conducted to study the recovery behavior of irradiated devices. The influence of linear energy transfer (LET) of radiations on damage mechanism is also discussed based on irradiation and annealing results. The results show that SiGe HBTs are more radiation hardened than Si BJTs.

The Inflection Point of Single Event Transient in SiGe HBT at a Cryogenic Temperature

Basing our findings on our previous pulsed laser testing results, we have experimentally demonstrated that there is an inflection point of a single event transient (SET) in the silicon-germanium heterojunction bipolar transistors (SiGe HBTs) with a decreasing temperature from +20 °C to −180 °C. Additionally, the changes in the parasitic resistivity of the carrier collection pathway due to incomplete ionization could play a key role. In this paper, we found that the incident-heavy ion’s parameters could also have an important impact on the SET inflection point by introducing the ion track structures generated by Geant4 simulation to the TCAD transient simulation. Heavy ion with a low linear energy transfer (LET) will not trigger the ion shunt effect of SiGe HBT and the inflection point will not occur until −200 °C. For high LET ions’ incidence, the high-density electron-hole pairs (EHPs) could significantly affect the parasitic resistivity on the pathway and lead to an earlier inflection point. The present results and methods could provide a new reference for the effective evaluation of single-event effects in bipolar transistors and circuits at cryogenic temperatures and provide new evidence of the SiGe technology’s potential for applications in extreme cryogenic environments.

Temperature dependence of single-event transients in SiGe heterojunction bipolar transistors for cryogenic applications

We experimentally demonstrate that the dominant mechanism of single-event transients in silicon-germanium heterojunction bipolar transistors (SiGe HBTs) can change with decreasing temperature from +20 °C to −180 °C. This is accomplished by using a new well-designed cryogenic experimental system suitable for a pulsed-laser platform. Firstly, when the temperature drops from +20 °C to −140 °C, the increased carrier mobility drives a slight increase in transient amplitude. However, as the temperature decreases further below −140 °C, the carrier freeze-out brings about an inflection point, which means the transient amplitude will decrease at cryogenic temperatures. To better understand this result, we analytically calculate the ionization rates of various dopants at different temperatures based on Altermatt’s new incomplete ionization model. The parasitic resistivities with temperature on the charge-collection pathway are extracted by a two-dimensional (2D) TCAD process simulation. In addition, we investigate the impact of temperature on the novel electron-injection process from emitter to base under different bias conditions. The increase of the emitter–base junction’s barrier height at low temperatures could suppress this electron-injection phenomenon. We have also optimized the built-in voltage equations of a high current compact model (HICUM) by introducing the impact of incomplete ionization. The present results and methods could provide a new reference for effective evaluation of single-event effects in bipolar transistors and circuits at cryogenic temperatures, and could provide a new evidence of the potential of SiGe technology in applications in extreme cryogenic environments.

BEOL Thermal Resistance Extraction in SiGe HBTs

A prior estimate of the impact of thermal resistance from the back-end-of-line (BEOL) metallization layers is crucial for an accurate circuit design and thermally aware device design. This article presents a robust technique to extract the thermal resistance component originating from the BEOL metal layers in silicon germanium heterojunction bipolar transistors (SiGe HBTs). The proposed technique is first tested on data generated using analytical equations and later validated with 3-D TCAD simulation. The results clearly show that the exact contribution of the BEOL to the overall thermal resistance is captured in the proposed approach. Finally, we verified the method using measured data obtained from fabricated SiGe HBT structures using Infineon B11HFC technology. The extracted parameters show reasonable accuracy and consistency across different emitter dimensions and BEOL configurations.

Challenges for Sige Bicmos in Advanced-Node SOI

D-band (110-170GHz) spectrum is gaining attention for various applications, including 6G mm-Wave, sub-THz sensing, and radar. These systems require lattice spacing for antenna elements at sub-1mm and a very low loss signal path from antenna to integrated chip. A highly efficient front-end in a very small form factor will be required for these systems. This drives the requirement for a monolithically integrated high-gain, high-efficiency front-end that also leverages the benefits of a high-speed / high-density digital CMOS. Silicon germanium (SiGe) heterojunction bipolar transistors (HBT) integrated along with a high-density CMOS provide such an all-silicon monolithic solution.The US government is fostering the expansion of “unique and differentiated domestic manufacturing” with funding through DARPA’s Technologies for Mixed-mode Ultra Scaled Integrated Circuits (T-MUSIC) [1] program to enable disruptive RF mixed-mode technologies by developing high performance RF analog integrated with advanced digital CMOS. Through the T-MUSIC program, DARPA seeks to: 1) advance RF and mixed-mode devices to support ultra-wideband RF frontends from HF to 100 GHz; 2) integrate those devices with high density digital CMOS electronics at the wafer scale to enable embedded digital intelligence; 3) develop and explore ultra-high resolution broadband mixed-mode circuit building blocks for DoD-relevant applications; 4) explore innovative device topologies and materials to form THz devices in an advanced digital CMOS fabrication platform; and 5) establish a domestic ecosystem that facilitates enduring DoD access to differentiated capabilities for high performance RF mixed-mode SoCs.Under T-MUSIC, GlobalFoundries is demonstrating BiCMOS on 45nm PDSOI, which is the focus of this paper, and 22nm FDSOI CMOS with goals of increasing HBT performance of fT/fMAX from 350/500 GHz to 400/600 GHz and 600/700 GHz. HBTs with fT/fMAX of 380/550GHz GHz have been demonstrated building upon previously published results [2]. This paper will touch on some of the challenges that were encountered in achieving that result and discuss those anticipated in future work.Achieving these results required scaling transistor dimensions. Vertical scaling of the emitter, base and collector layers, with higher doping concentrations, reduces transit time but results in higher current densities and higher electric fields. Lateral scaling of the transistor structure reduces parasitic capacitance and resistance but concentrate the power dissipation in a smaller area. The thermal conductivity of silicon is 148W/m-K whereas that of silicon dioxide is ~1.4W/m-K. Even a thin layer of oxide will significantly increase the self-heating of the HBT. Therefore, we replace the SOI with coplanar epitaxy in regions where the HBTs are formed.The vertical scaling of the HBT requires limiting the thermal cycles that the HBT will experience during processing and suggests forming the HBT as late as possible in the CMOS process. However, the thermal cycles associate with the epitaxy and film depositions to form the HBT impact the CMOS transistors which suggests forming the HBT early in the process. We found a point in the process that offers the best compromise minimizing the impact to the doped-channel PDSOI CMOS while achieving the HBT performance goals. Work is just beginning on integration tradeoffs for FDSOI with metal gate and high-K dielectrics.Advanced-node CMOS processes can form components having smaller dimensions which offers advantages for lateral scaling but also presents challenges for forming the HBT. The contact height in 45nm is significantly less than the height of the HBT structure used in GF’s 9HP process. We changed the formation of the emitter and base so that the emitter and base contacts are almost coplanar in contrast to 9HP where the emitter was almost twice the height of the base. This problem is being further exasperated as we migrate to 22nm.The shrinking of BEOL wiring dimensions, along with the ability of the HBT to drive high currents, presents challenges in designing within limits imposed by electromigration. The use of wider wires is constrained by metal density rules. The use of stacked metal levels and redundant vias impact the parasitic capacitances and resistances of the interconnects.The paper and presentation will review these, and other challenges encountered in achieving BiCMOS integration of SiGe HBTs with fT/fMAX of 380/550GHz GHz [see figure] on a 45nm PDSOI CMOS and touch future work.This research was developed with funding from the Defense Advanced Research Projects Agency (DARPA) and is Approved for Public Release, Distribution Unlimited. The views, opinions and/or findings expressed are those of the author and should not be interpreted as representing the official views or policies of the Department of Defense or the U.S. Government.[1] https://www.darpa.mil/attachments/T-MUSIC_Proposers%20Day_Presentations_Combined.pdf [2] J. Pekarik et al., 2021 IEEE BCICTS, 2021, pp. 1-4, Figure 1

Radiation Hardened Millimeter-Wave Receiver Implemented in 90-nm, SiGe HBT Technology

This article presents novel radiation hardening design techniques to substantially reduce the single-event effects (SEEs) on high-frequency receivers subject to various radiations when operating in space. A <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$W$ </tex-math></inline-formula> -band (75–110 GHz) receiver front-end implemented in Global Foundry’s 90-nm silicon–germanium (SiGe) BiCMOS technology is used for studying SEE and investigating the effectiveness of the proposed techniques. Specifically, the mixer is modified to allow for different modes of operation in addition to introducing matching considerations between the mixer’s gain and switching stages. The receiver includes integrated high-frequency signal sources to provide the input radio frequency (RF) and local oscillator (LO) signals for full operation of the proposed millimeter-wave (mmW) receiver. Measurements are taken while the receiver is in normal operation (RF and LO are applied). The design techniques are carefully analyzed via extensive simulations using equivalent transient current pulses obtained from calibrated technology computer-aided design (TCAD) simulations. A two-photon absorption (TPA) pulsed laser experiment is used to induce transient currents in the silicon–germanium heterojunction bipolar transistor (SiGe HBT) circuit. Various devices within the mixer are hit from the back side through a hole in the designed printed circuit board (PCB). The propagated transients are then captured using a high-speed oscilloscope at the output of the receiver. The measurement results, supported by simulations and analysis, validate the robustness of the proposed radiation hardened receiver to SEE.

Wideband SiGe down-converter for millimeter-wave radio astronomy applications

A Q-band down-converter module with high conversion gain (CG) is presented for a wideband radio astronomy receiver. This down-converter module is designed on a silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) process (0.13 μm) to realize high CG, low LO power operation, and wideband frequency impedance matching for RF/LO/IF ports. The down-converter consists of a double-balanced Gilbert mixing core with on-chip RF/LO transformer baluns, an IF buffer, and bandpass filter. The performance of the down converter is largely dependent on the passive components and signal line interconnection. The design of all passive structures is analyzed and optimized with FEM simulations for a high-quality factor to minimize losses and parasitic effects. This module achieves 8 dB of CG at a low LO power of −6 dBm over a wide RF bandwidth from 28 to 56 GHz and IF bandwidth from 6 to 18 GHz. It demonstrates LO-to-IF/LO-to-RF/RF-to-IF isolations > dB / 40 dB/35 dB, respectively. The critical FEM simulation is described in the design of this high-density SiGe HBT RF circuit. The measured performance confirms the simulation results. The module meets the original design requirements of the DVA-2 Q-band receiver.

Sensitivity study of the SiGe heterojunction bipolar transistor single event effect based on pulsed laser and technology computer-aided design simulation

The single event effect of a silicon–germanium heterojunction bipolar transistor (SiGe HBT) was thoroughly investigated. By considering the worst bias condition, the sensitive area of the proposed device was scanned with a pulsed laser. With variation of the collector bias and pulsed laser incident energy, the single event transient of the SiGe HBT was studied. Moreover, the single event transient produced by laser irradiation at a wavelength of 532 nm was more pronounced than at a wavelength of 1064 nm. Finally, the impact of the equivalent linear energy transfer of the 1064 nm pulsed laser on the single event transient was qualitatively examined by performing technology computer-aided design simulations, and a good consistency between the experimental data and the simulated outcomes was attained.

50 MeV lithium ion irradiation studies on silicon-germanium heterojunction bipolar transistors at low temperature

Total dose effects of 50 MeV lithium ions irradiation on 200GHz silicon-germanium heterojunction bipolar transistors (SiGe HBT) in the dose ranging from 1 to 30 Mrad were examined at low temperature. The HBTs were subjected to 50 MeV lithium ions at 150 K and 300 K. Pre- and post-irradiation I-V characteristics were studied at 300 K. The comparison of low temperature irradiation results with room temperature results was made systematically. The radiation caused generation-recombination trapped carriers increase the base current (IB) of HBTs and is proportional to the total dose. However, the transistors irradiated at 150 K show lesser degradation than devices irradiated at 300 K. Stopping and range of ions in matter (SRIM) study was also carried out to know the impact of lithium ions on different regions of SiGe HBT.

Angular dependence of proton-induced single event transient in silicon-germanium heterojunction bipolar transistors

We investigate the angular dependence of proton-induced single event transient (SET) in silicon-germanium heterojunction bipolar transistors. Experimental results show that the overall SET cross section is almost independent of proton incident angle. However, the proportion of SET events with long duration and high integral charge collection grows significantly with the increasing angle. Monte Carlo simulations demonstrate that the integral cross section of proton incident events with high ionizing energy deposition in the sensitive volume tends to be higher at larger incident angles, which is associated with the angular distribution of proton-induced secondary particles and the geometry of sensitive volume.

Investigation on the performance dependence of proton radiated SiGe HBTs with emitter area and temperature

The DC and AC performances of proton radiated Silicon-Germanium (SiGe) Heterojunction Bipolar Transistors (HBTs) with different emitter areas at liquid nitrogen temperature (77 K), room temperature and heating hotplate (393 K) were presented in this work. Performance dependence on the emitter area and temperature was investigated. Results showed that SiGe HBTs with a large emitter area had more damage by proton radiation. Furthermore, the SiGe HBTs showed better tolerance to proton radiation at extreme temperatures than at room temperature. To reveal the underlying mechanism, the radiated SiGe HBTs were modeled based on the device structure and parameters. The electron density, Shockley–Read–Hall (SRH) recombination and carrier mobility were extracted from the device model and demonstrated to have major impacts on the performance dependence of the radiated SiGe HBTs. The results provide useful guidance for the application of SiGe HBTs at extreme environments.

A 20-44 GHz Wideband LNA Design Using the SiGe Technology for 5G Millimeter-Wave Applications.

This paper presents the design and implementation of a low-noise amplifier (LNA) for millimeter-wave (mm-Wave) 5G wireless applications. The LNA was based on a common-emitter configuration with cascode amplifier topology using an IHP’s 0.13 μm Silicon Germanium (SiGe) heterojunction bipolar transistor (HBT) whose f_T/f_MAX/gate-delay is 360/450 GHz/2.0 ps, utilizing transmission lines for simultaneous noise and input matching. A noise figure of 3.02–3.4 dB was obtained for the entire wide bandwidth from 20 to 44 GHz. The designed LNA exhibited a gain (S_21) greater than 20 dB across the 20–44 GHz frequency range and dissipated 9.6 mW power from a 1.2 V supply. The input reflection coefficient (S_11) and output reflection coefficient (S_22) were below −10 dB, and reverse isolation (S_12) was below −55 dB for the 20–44 GHz frequency band. The input 1 dB (P1dB) compression point of −18 dBm at 34.5 GHz was obtained. The proposed LNA occupies only a 0.715 mm2 area, with input and output RF (Radio Frequency) bond pads. To the authors’ knowledge, this work evidences the lowest noise figure, lowest power consumption with reasonable highest gain, and highest bandwidth attained so far at this frequency band in any silicon-based technology.

Quasiballistic electron transport in cryogenic SiGe HBTs studied using an exact, semi-analytic solution to the Boltzmann equation

Silicon–germanium heterojunction bipolar transistors (HBTs) are of interest as low-noise microwave amplifiers due to their competitive noise performance and low cost relative to III–V devices. The fundamental noise performance limits of HBTs are thus of interest, and several studies report that quasiballistic electron transport across the base is a mechanism leading to cryogenic non-ideal IV characteristics that affect these limits. However, this conclusion has not been rigorously tested against theoretical predictions because prior studies modeled electron transport with empirical approaches or approximate solutions of the Boltzmann equation. Here, we study non-diffusive transport in narrow-base SiGe HBTs using an exact, semi-analytic solution of the Boltzmann equation based on an asymptotic expansion approach. We find that the computed transport characteristics are inconsistent with experiments, implying that quasiballistic electron transport is unlikely to be the origin of cryogenic non-ideal IV characteristics. Our work helps to identify the mechanisms governing the lower limits of the microwave noise figure of cryogenic HBT amplifiers.

Investigation of Base Transport Mechanism in Silicon-Germanium Heterojunction Bipolar Transistor Operating over Wide Temperature Range

A high breakdown voltage silicon-germanium heterojunction bipolar transistor operated over a wide temperature range from 300 K to 10 K has been investigated. The measured Gummel characteristics illustrate that the collector current and base current both shift to the higher voltage as the temperature decreases. The fT/fmax are extracted to be 23/40 GHz at 300K, 28/40 GHz at 90 K, and 25/37GHz at 10K, respectively. The effective amplification range becomes narrow as the temperature decreases. And the ideality factor of base current in the low current region is shown to be temperature-dependent and its value is much larger than 2 at cryogenic temperatures. This phenomenon indicates that the base current is not only contributed by drift, diffusion, and Shockley-Read-Hall recombination, but also by trap-assisted tunneling. The Hurkx local trap-assisted tunneling has been used to analyze the non-ideal base transport mechanism. And a calibrated TCAD device model is developed to further verify this non-ideal transport mechanism.

Sub-THz and THz SiGe HBT Electrical Compact Modeling

From the perspectives of characterized data, calibrated TCAD simulations and compact modeling, we present a deeper investigation of the very high frequency behavior of state-of-the-art sub-THz silicon germanium heterojunction bipolar transistors (SiGe HBTs) fabricated with 55-nm BiCMOS process technology from STMicroelectronics. The TCAD simulation platform is appropriately calibrated with the measurements in order to aid the extraction of a few selected high-frequency (HF) parameters of the state-of-the-art compact model HICUM, which are otherwise difficult to extract from traditionally prepared test-structures. Physics-based strategies of extracting the HF parameters are elaborately presented followed by a sensitivity study to see the effects of the variations of HF parameters on certain frequency-dependent characteristics until 500 GHz. Finally, the deployed HICUM model is evaluated against the measured s-parameters of the investigated SiGe HBT until 500 GHz.

Meander-Type Lines: An Innovative Design for On-Wafer TRL Calibration for mmW and Sub-mmW Frequencies Measurements

In this article, we introduce novel transmission line standards for on-wafer thru-reflect-line (TRL) calibration employing a meandering architecture, which aims to keep the interprobe distance constant and avoid any probe separation during the measurement process, yet establishing the required signal path length between the ports. Measurements will be performed up to 500 GHz on passive de-embedding structures and on a silicon-germanium heterojunction bipolar transistor (SiGe HBT); they will be calibrated with both a classic approach and this novel “meander-type” technique. Furthermore, measurements will be evaluated by means of electromagnetic (EM) simulation: For this purpose, we will make use of Ansys High-Frequency Structure Simulator (HFSS) on passive test structures. Finally, a novel joint EM-SPICE cosimulation analysis will allow us to provide simulated data for a transistor, thus extending our study to active devices; this will allow a complete characterization of the measurements and an insight on the physical limits of our calibration technique.

Variability of p-n Junctions and SiGe HBTs at Cryogenic Temperatures

This investigation examines the physical mechanisms that can increase the variability of both p-n junctions and silicon-germanium heterojunction bipolar transistors (SiGe HBTs) at cryogenic temperatures. The important operative mechanisms responsible for device parameter variability include bandgap narrowing due to heavy doping, mechanical stress, and the Ge profile. The impact of direct tunneling on cryogenic parameter variability in SiGe HBTs is also examined. Measurement results are compared with TCAD simulations to provide additional insights, and possible mitigation methods are discussed.