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(1 - 6 of 6)
- Title
- On-Chip Electro-Static Discharge (ESD) Protection for Radio-Frequency Integrated Circuits.
- Creator
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Cui, Qiang, Liou, Juin, Yuan, Jiann-Shiun, Wu, Xinzhang, Haralambous, Michael, Shen, Zheng, Deppe, Dennis, University of Central Florida
- Abstract / Description
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Electrostatic Discharge (ESD) phenomenon is a common phenomenon in daily life and it could damage the integrated circuit throughout the whole cycle of product from the manufacturing. Several ESD stress models and test methods have been used to reproduce ESD events and characterize ESD protection device's performance. The basic ESD stress models are: Human Body Model (HBM), Machine Model (MM), and Charged Device Model (CDM). On-chip ESD protection devices are widely used to discharge ESD...
Show moreElectrostatic Discharge (ESD) phenomenon is a common phenomenon in daily life and it could damage the integrated circuit throughout the whole cycle of product from the manufacturing. Several ESD stress models and test methods have been used to reproduce ESD events and characterize ESD protection device's performance. The basic ESD stress models are: Human Body Model (HBM), Machine Model (MM), and Charged Device Model (CDM). On-chip ESD protection devices are widely used to discharge ESD current and limit the overstress voltage under different ESD events. Some effective ESD protection devices were reported for low speed circuit applications such as analog ICs or digital ICs in CMOS process. On the contrast, only a few ESD protection devices available for radio frequency integrated circuits (RF ICs). ESD protection for RF ICs is more challenging than traditional low speed CMOS ESD protection design because of the facts that: (1) Process limitation: High-performance RF ICs are typically fabricated in compound semiconductor process such as GaAs pHEMT and SiGe HBT process. And some proved effective ESD devices (e.g. SCR) are not able to be fabricated in those processes due to process limitation. Moreover, compound semiconductor process has lower thermal conductivity which will worsen its ESD damage immunity. (2) Parasitic capacitance limitation: Even for RF CMOS process, the inherent parasitic capacitance of ESD protection devices is a big concern. Therefore, this dissertation will contribute on ESD protection designs for RF ICs in all the major processes including GaAs pHEMT, SiGe BiCMOS and standard CMOS.The ESD protection for RF ICs in GaAs pHEMT process is very difficult, and the typical HBM protection level is below 1-kV HBM level. The first part of our work is to analyze pHEMT's snapback, post-snapback saturation and thermal failure under ESD stress using TLP-like Sentaurus TCAD simulation. The snapback is caused by virtual bipolar transistor due to large electron-hole pairs impacted near drain region. Post-snapback saturation is caused by temperature-induced mobility degradation due to III-V compound semiconductor materials' poor thermal conductivity. And thermal failure is found to be caused by hot spot located in pHEMT's InGaAs layer. Understanding of these physical mechanisms is critical to design effective ESD protection device in GaAs pHEMT process. Several novel ESD protection devices were designed in 0.5um GaAs pHEMT process. The multi-gate pHEMT based ESD protection devices in both enhancement-mode and depletion-mode were reported and characterized then. Due to the multiple current paths available in the multi-gate pHEMT, the new ESD protection clamp showed significantly improved ESD performances over the conventional single-gate pHEMT ESD clamp, including higher current discharge capability, lower on-state resistance, and smaller voltage transient. We proposed another further enhanced ESD protection clamp based on a novel drain-less, multi-gate pHEMT in a 0.5um GaAs pHEMT technology. Based on Barth 4002 TLP measurement results, the ESD protection devices proposed in this chapter can improve the ESD level from 1-kV (0.6 A It2) to up to 8-kV ((>) 5.2 A It2) under HBM. Then we optimized SiGe-based silicon controlled rectifiers (SiGe SCR) in SiGe BiCMOS process. SiGe SCR is considered a good candidate ESD protection device in this process. But the possible slow turn-on issue under CDM ESD events is the major concern. In order to optimize the turn-on performance of SiGe SCR against CDM ESD, the Barth 4012 very fast TLP (vfTLP) and vfTLP-like TCAD simulation were used for characterization and analysis. It was demonstrated that a SiGe SCR implemented with a P PLUG layer and minimal PNP base width can supply the smallest peak voltage and fastest response time which is resulted from the fact that the impact ionization region and effective base width in the SiGe SCR were reduced due to the presence of the P PLUG layer. This work demonstrated a practical approach for designing optimum ESD protection solutions for the low-voltage/radio frequency integrated circuits in SiGe BiCMOS process.In the end, we optimized SCRs in standard silicon-based CMOS process to supply protection for high speed/radio-frequency ICs. SCR is again considered the best for its excellent current handling ability. But the parasitic capacitance of SCRs needs to be reduced to limit SCR's impact to RF performance. We proposed a novel SCR-based ESD structure and characterize it experimentally for the design of effective ESD protection in high-frequency CMOS based integrated circuits. The proposed SCR-based ESD protection device showed a much lower parasitic capacitance and better ESD performance than the conventional SCR and a low-capacitance SCR reported in the literature. The physics underlying the low capacitance was explained by measurements using HP 4284 capacitance meter.Throughout the dissertation work, all the measurements are mainly conducted using Barth 4002 transimission line pulsing (TLP) and Barth 4012 very fast transmission line pulsing (vfTLP) testers. All the simulation was performed using Sentaurus TCAD tool from Synopsys.
Show less - Date Issued
- 2013
- Identifier
- CFE0004668, ucf:49848
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004668
- Title
- STUDY OF INGAAS LDMOS FOR POWER CONVERSION APPLICATIONS.
- Creator
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Liu, Yidong, Yuan, Jiann S., University of Central Florida
- Abstract / Description
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In this work an n-channel In0.65Ga0.35As LDMOS with Al2O3 as gate dielectric is investigated. Instead of using traditional Si process for LDMOS, we suggest In0.65Ga0.35As as substitute material due to its higher electron mobility and its promising for power applications. The proposed 0.5-μm channel-length LDMOS cell is studied through device TCAD simulation tools. Due to different gate dielectric, comprehensive comparisons between In0.65Ga0.35As LDMOS and Si LDMOS are made in two ways,...
Show moreIn this work an n-channel In0.65Ga0.35As LDMOS with Al2O3 as gate dielectric is investigated. Instead of using traditional Si process for LDMOS, we suggest In0.65Ga0.35As as substitute material due to its higher electron mobility and its promising for power applications. The proposed 0.5-μm channel-length LDMOS cell is studied through device TCAD simulation tools. Due to different gate dielectric, comprehensive comparisons between In0.65Ga0.35As LDMOS and Si LDMOS are made in two ways, structure with the same cross-sectional dimension, and structure with different thickness of gate dielectric to achieve the same gate capacitance. The on-resistance of the new device shows a big improvement with no degradation on breakdown voltage over traditional device. Also it is indicated from these comparisons that the figure of merit(FOM) Ron·Qg of In0.65Ga0.35As LDMOS shows an average of 91.9% improvement to that of Si LDMOS. To further explore the benefit of using In0.65Ga0.35As LDMOS as switch in power applications, DC-DC buck converter is utilized to observe the performance of LDMOS in terms of power efficiency. The LDMOS performance is experimented with operation frequency of the circuit sweeping in the range from 100 KHz to 100 MHz. It turns out InGaAs LDMOS is good candidate for power applications.
Show less - Date Issued
- 2009
- Identifier
- CFE0002686, ucf:48217
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002686
- Title
- TUNABLE TERAHERTZ DETECTORS BASED ON PLASMON EXCIATION IN TWO DIMENSIONAL ELECTRON GASES IN INGAAS/INP AND ALGAN/GAN HEMT.
- Creator
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Saxena, Himanshu, Peale, Robert, University of Central Florida
- Abstract / Description
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The observation of voltage-tunable plasmon resonances in the terahertz range in two dimensional electron gas (2-deg) of a high electron mobility transistor (HEMT) fabricated from the InGaAs/InP and AlGaN/GaN materials systems is reported. The devices were fabricated from a commercial HEMT wafer by depositing source and drain contacts using standard photolithography process and a semi-transparent gate contact that consisted of a 0.5 µm period transmission grating formed by electron-beam...
Show moreThe observation of voltage-tunable plasmon resonances in the terahertz range in two dimensional electron gas (2-deg) of a high electron mobility transistor (HEMT) fabricated from the InGaAs/InP and AlGaN/GaN materials systems is reported. The devices were fabricated from a commercial HEMT wafer by depositing source and drain contacts using standard photolithography process and a semi-transparent gate contact that consisted of a 0.5 µm period transmission grating formed by electron-beam lithography. Narrow-band resonant absorption of THz radiation was observed in transmission in the frequency range 10–100 cm-1. The resonance frequency depends on the gate voltage-tuned sheet-charge density of the 2deg. The fundamental and higher resonant harmonics were observed to shift towards lower frequencies with the implementation of negative gate bias. The theory of interaction of sub millimeter waves with 2deg through corrugated structure on top has been applied to calculate and understand the phenomena of resonant plasmon excitations. The observed separation of resonance fundamental from its harmonics and their shift with gate bias follows theory, although the absolute frequencies are lower by about a factor of 2-3 in InGaAs/InP system. However, calculated values match much better with AlGaN/GaN system.
Show less - Date Issued
- 2009
- Identifier
- CFE0002912, ucf:47994
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002912
- Title
- RELIABILITY STUDY OF INGAP/GAAS HETEROJUNCTION BIPOLAR TRANSISTOR MMIC TECHNOLOGY BY CHARACTERIZATION, MODELING AND SIMULATION.
- Creator
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LIU, XIANG, Liou, Juin J., University of Central Florida
- Abstract / Description
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Recent years have shown real advances of microwave monolithic integrated circuits (MMICs) for millimeter-wave frequency systems, such as wireless communication, advanced imaging, remote sensing and automotive radar systems, as MMICs can provide the size, weight and performance required for these systems. Traditionally, GaAs pseudomorphic high electron mobility transistor (pHEMT) or InP based MMIC technology has dominated in millimeter-wave frequency applications because of their high fT and...
Show moreRecent years have shown real advances of microwave monolithic integrated circuits (MMICs) for millimeter-wave frequency systems, such as wireless communication, advanced imaging, remote sensing and automotive radar systems, as MMICs can provide the size, weight and performance required for these systems. Traditionally, GaAs pseudomorphic high electron mobility transistor (pHEMT) or InP based MMIC technology has dominated in millimeter-wave frequency applications because of their high fT and fmax as well as their superior noise performance. But these technologies are very expensive. Thus, for low cost and high performance applications, InGaP/GaAs heterojunction bipolar transistors (HBTs) are quickly becoming the preferred technology to be used due to their inherently excellent characteristics. These features, together with the need for only one power supply to bias the device, make InGaP/GaAs HBTs very attractive for the design of high performance fully integrated MMICs. With the smaller dimensions for improving speed and functionality of InGaP/GaAs HBTs, which dissipate large amount of power and result in heat flux accumulated in the device junction, technology reliability issues are the first concern for the commercialization. As the thermally triggered instabilities often seen in InGaP/GaAs HBTs, a carefully derived technique to define the stress conditions of accelerated life test has been employed in our study to acquire post-stress device characteristics for the projection of long-term device performance degradation pattern. To identify the possible origins of the post-stress device behaviors observed experimentally, a two dimensional (2-D) TCAD numerical device simulation has been carried out. Using this approach, it is suggested that the acceptor-type trapping states located in the emitter bulk are responsible for the commonly seen post-stress base current instability over the moderate base-emitter voltage region. HBT-based MMIC performance is very sensitive to the variation of core device characteristics and the reliability issues put the limit on its radio frequency (RF) behaviors. While many researchers have reported the observed stress-induced degradations of GaAs HBT characteristics, there has been little published data on the full understanding of stress impact on the GaAs HBT-based MMICs. If care is not taken to understand this issue, stress-induced degradation paths can lead to built-in circuit failure during regular operations. However, detection of this failure may be difficult due to the circuit complexity and lead to erroneous data or output conditions. Thus, a practical and analytical methodology has been developed to predict the stress impacts on HBT-based MMICs. It provides a quick way and guidance for the RF design engineer to evaluate the circuit performance with reliability considerations. Using the present existing EDA tools (Cadance SpectreRF and Agilent ADS) with the extracted pre- and post-stress transistor models, the electrothermal stress effects on InGaP/GaAs HBT-based RF building blocks including power amplifier (PA), low-noise amplifier (LNA) and oscillator have been systematically evaluated. This provides a potential way for the RF/microwave industry to save tens of millions of dollars annually in testing costs. The world now stands at the threshold of the age of advanced GaAs HBT MMIC technology and researchers have been exploring here for years. The reliability of GaAs HBT technology is no longer the post-design evaluation, but the pre-design consideration. The successful and fruitful results of this dissertation provide methods and guidance for the RF designers to achieve more reliable RF circuits with advanced GaAs HBT technology in the future.
Show less - Date Issued
- 2011
- Identifier
- CFE0003904, ucf:48744
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003904
- Title
- MONTE CARLO SIMULATION OF HOLE TRANSPORT AND TERAHERTZ AMPLIFICATION IN MULTILAYER DELTA DOPED SEMICONDUCTOR STRUCTURES.
- Creator
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Dolguikh, Maxim, Peale, Robert, University of Central Florida
- Abstract / Description
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Monte Carlo method for the simulation of hole dynamics in degenerate valence subbands of cubic semiconductors is developed. All possible intra- and inter-subband scattering rates are theoretically calculated for Ge, Si, and GaAs. A far-infrared laser concept based on intersubband transitions of holes in p-type periodically delta-doped semiconductor films is studied using numerical Monte-Carlo simulation of hot hole dynamics. The considered device consists of monocrystalline pure Ge layers...
Show moreMonte Carlo method for the simulation of hole dynamics in degenerate valence subbands of cubic semiconductors is developed. All possible intra- and inter-subband scattering rates are theoretically calculated for Ge, Si, and GaAs. A far-infrared laser concept based on intersubband transitions of holes in p-type periodically delta-doped semiconductor films is studied using numerical Monte-Carlo simulation of hot hole dynamics. The considered device consists of monocrystalline pure Ge layers periodically interleaved with delta-doped layers and operates with vertical or in-plane hole transport in the presence of a perpendicular in-plane magnetic field. Inversion population on intersubband transitions arises due to light hole accumulation in E B fields, as in the bulk p-Ge laser. However, the considered structure achieves spatial separation of hole accumulation regions from the doped layers, which reduces ionized-impurity and carrier-carrier scattering for the majority of light holes. This allows remarkable increase of the gain in comparison with bulk p-Ge lasers. Population inversion and gain sufficient for laser operation are expected up to 77 K. Test structures grown by chemical vapor deposition demonstrate feasibility of producing the device with sufficient active thickness to allow quasioptical electrodynamic cavity solutions. The same device structure is considered in GaAs. The case of Si is much more complicated due to strong anisotropy of the valence band. The primary new result for Si is the first consideration of the anisotropy of optical phonon scattering for hot holes.
Show less - Date Issued
- 2005
- Identifier
- CFE0000863, ucf:46672
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000863
- Title
- Non-Degenerate Two Photon Gain in Bulk Gallium Arsenide.
- Creator
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Turnbull, Brendan, Hagan, David, Vanstryland, Eric, Christodoulides, Demetrios, University of Central Florida
- Abstract / Description
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The purpose of this thesis is to investigate the nonlinear phenomena known as doubly-stimulated, non-degenerate two-photon emission (ND-2PE) in Gallium Arsenide (GaAs). 2PE refers to the simultaneous emission of two-photons as electrons move from the conduction band in a direct gap semiconductor to the valence band. Following the same path for describing one-photon emission (1PE) we describe 2PE as a product of the irradiance, I, and the negative of the loss which in this case is two-photon...
Show moreThe purpose of this thesis is to investigate the nonlinear phenomena known as doubly-stimulated, non-degenerate two-photon emission (ND-2PE) in Gallium Arsenide (GaAs). 2PE refers to the simultaneous emission of two-photons as electrons move from the conduction band in a direct gap semiconductor to the valence band. Following the same path for describing one-photon emission (1PE) we describe 2PE as a product of the irradiance, I, and the negative of the loss which in this case is two-photon absorption, ?_2, the negative coming from the population inversion. We attempt to observe 2PE by using a frequency non-degenerate pump-probe experiment in which a third beam optically excites a 4 (&)#181;m thick GaAs sample. We use non-degenerate beams in hopes of utilizing the 3-orders of magnitude enhancement seen in two-photon absorption (2PA) by going to extreme nondegeneracy (END) to enhance 2PE. GaAs is chosen due to the availability of the appropriate wavelengths, the maturity of the GaAs technology, its use in optoelectronic devices and its ability to be electrically pumped. During the experimental development we learn how to effectively etch and manipulate thin GaAs samples and model the transmission spectrum of these samples using thin film transmission matrices. We are able to match the measured transmission spectrum with the theoretical transmission spectrum. Here we etch the bulk GaAs left on the sample leaving only the 4 (&)#181;m thickness of molecular beam epitaxial grown GaAs plus additional layers of aluminum gallium arsenide (AlGaAs). These samples were grown for us by Professor Gregory Salamo of the University of Arkansas.Using the pump-probe experiment on the 4 (&)#181;m GaAs sample, we measure the change of the 2PA due to the presence of optically excited carriers. The goal is to reduce the 2PA signal to zero and then invert the 2PA signal indicating an increase in transmission indicative of 2PE when the population is inverted. Our results show that we achieve a 45% reduction in the 2PA signal in a 4 ?m thick GaAs sample due to the excited carriers. Unfortunately, we currently cannot experimentally determine whether the reduction is strictly due to free-carrier absorption (FCA) of our pump or possibly due to a change in the two-photon absorption coefficient. We measure the transmission of various wavelengths around the bang gap of GaAs as a function of excitation wavelength and achieve a transmittance of ~80% which we attribute to possibly be one photon gain (1PG) at 880 nm. We also go to cryogenic temperatures to concentrate the carriers near the bottom of the conduction band and improve the theoretical gain coefficient for 2PE. Unfortunately, we do not observe a measurable change in 2PA with the addition of optically excited carriers. Along with FCA of our infrared pump we suspect that the difficulties in this first set of experiments are also a result or radiative recombination due to amplified spontaneous emission reducing our free carrier density along with the fact that 4 ?m is too thick for uniform excitation. We now have 1 ?m samples from Professor Gregory Salamo which we hope will give better and more definitive results.
Show less - Date Issued
- 2013
- Identifier
- CFE0004762, ucf:49776
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004762
