Thermal Stability of Plasma-enhanced Chemical Vapor Deposition Silicon Nitride Passivation on AlGaN/GaN High-electron-mobility Transistors PDF Download
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Author: Minh-Trang Teresa Ha
Publisher:
ISBN:
Category :
Languages : en
Pages : 43
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Book Description
AlGaN/GaN HEMTs are the most promising high power switching devices. The material properties of III-nitrides are exceptionally better than that of Si and GaAs. GaN-based devices have been recorded to have higher operating temperatures and higher breakdown field due to the wide bandgap. AlGaN/GaN heterostructures forms 2DEG without doping due to the spontaneous polarization. The performance and reliability of AlGaN/GaN HEMTs are dependent on the structure of the AlGaN/GaN heterostructures. Surface passivation has been proven to improve the 2DEG conductivity and device performance. 20 nm of plasma-enhanced chemical vapor deposition (PECVD) SiN was deposited on AlGaN/GaN HEMTs, and the PECVD SiN passivated sample demonstrated higher carrier concentration of 9.88 ? 1012 cm-2 compared to the un-passivated sample, 8.08 ? 1012 cm-2. High temperature annealing is an important processing step in the fabrication of the devices, and the effects have shown to improve the DC and RF performance. High temperature annealing may affect the structure and the 2DEG conductivity. The annealing effects modifies the AlGaN layer and the AlGaN/GaN interface. Herein, we present the a study on the thermal stability of the PECVD SiN passivation layer on AlGaN/GaN HEMT structures at high temperature anneals. High-resolution x-ray diffraction (HRXRD) measurements were used to investigate the strain of AlGaN layer, and Hall measurements were used to investigate the 2DEG conductivity. PECVD SiN passivated and un-passivated AGaN/GaN HEMTs structure underwent high temperature thermal anneals for 30 minutes in N2. The starting temperature of the annealing is 400?C with step of 50?C until degradation. Degradation was determined through Hall sheet resistivity and mobility measurements. The ending annealed temperature is 1000 ?C and 700 ?C for passivated and control samples, respectively. From no anneal to degradation temperature, the 2DEG conductivity dropped by 15% and 34% for passivated and un-passivated samples, respectively. The HRXRD measurements found the change in-plane strain of the AlGaN layer after high temperature anneals. Higher in-plane strain showed higher 2DEG conductivity. In-plane strain from no anneal to degradation temperature dropped from 2% and 7% for passivated and un-passivated samples, respectively. Therefore, the passivated sample demonstrated to be more stable at high temperatures. The SiN passivation layer adds tensile stress to the AlGaN layer thus increased the piezoelectric effect and 2DEG conductivity.
Author: Minh-Trang Teresa Ha
Publisher:
ISBN:
Category :
Languages : en
Pages : 43
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Book Description
AlGaN/GaN HEMTs are the most promising high power switching devices. The material properties of III-nitrides are exceptionally better than that of Si and GaAs. GaN-based devices have been recorded to have higher operating temperatures and higher breakdown field due to the wide bandgap. AlGaN/GaN heterostructures forms 2DEG without doping due to the spontaneous polarization. The performance and reliability of AlGaN/GaN HEMTs are dependent on the structure of the AlGaN/GaN heterostructures. Surface passivation has been proven to improve the 2DEG conductivity and device performance. 20 nm of plasma-enhanced chemical vapor deposition (PECVD) SiN was deposited on AlGaN/GaN HEMTs, and the PECVD SiN passivated sample demonstrated higher carrier concentration of 9.88 ? 1012 cm-2 compared to the un-passivated sample, 8.08 ? 1012 cm-2. High temperature annealing is an important processing step in the fabrication of the devices, and the effects have shown to improve the DC and RF performance. High temperature annealing may affect the structure and the 2DEG conductivity. The annealing effects modifies the AlGaN layer and the AlGaN/GaN interface. Herein, we present the a study on the thermal stability of the PECVD SiN passivation layer on AlGaN/GaN HEMT structures at high temperature anneals. High-resolution x-ray diffraction (HRXRD) measurements were used to investigate the strain of AlGaN layer, and Hall measurements were used to investigate the 2DEG conductivity. PECVD SiN passivated and un-passivated AGaN/GaN HEMTs structure underwent high temperature thermal anneals for 30 minutes in N2. The starting temperature of the annealing is 400?C with step of 50?C until degradation. Degradation was determined through Hall sheet resistivity and mobility measurements. The ending annealed temperature is 1000 ?C and 700 ?C for passivated and control samples, respectively. From no anneal to degradation temperature, the 2DEG conductivity dropped by 15% and 34% for passivated and un-passivated samples, respectively. The HRXRD measurements found the change in-plane strain of the AlGaN layer after high temperature anneals. Higher in-plane strain showed higher 2DEG conductivity. In-plane strain from no anneal to degradation temperature dropped from 2% and 7% for passivated and un-passivated samples, respectively. Therefore, the passivated sample demonstrated to be more stable at high temperatures. The SiN passivation layer adds tensile stress to the AlGaN layer thus increased the piezoelectric effect and 2DEG conductivity.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Three different passivation layers (SiN(x), MgO, and Sc2O3) were examined for their effectiveness in mitigating surface-state-induced current collapse in AlGaN/GaN high electron mobility transistors (HEMTs). The plasma-enhanced chemical vapor deposited SiN(x) produced 70 to 75 percent recovery of the drain-source current, independent of whether SIH4/NH3 or SiD4/ND3 plasma chemistries were employed. Both the Sc2O3 and MgO produced essentially complete recover of the current in GaN-cap HEMP structures and 80 to 90 percent recovery in AlGaN-cap structures. The Sc2O3 had superior long-term stability, with no change in HEMT behavior over 5 months of aging.
Author: Tuomas Hänninen
Publisher: Linköping University Electronic Press
ISBN: 9176853748
Category :
Languages : en
Pages : 73
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Book Description
Silicon nitride and silicon nitride-based ceramics have several favorable material properties, such as high hardness and good wear resistance, which makes them important materials for the coating industry. This thesis focuses the synthesis of silicon nitride, silicon oxynitride, and silicon carbonitride thin films by reactive magnetron sputtering. The films were characterized based on their chemical composition, chemical bonding structure, and mechanical properties to link the growth conditions to the film properties. Silicon nitride films were synthesized by reactive high power impulse magnetron sputtering (HiPIMS) from a Si target in Ar/N2 atmospheres, whereas silicon oxynitride films were grown by using nitrous oxide as the reactive gas. Silicon carbonitride was synthesized by two different methods. The first method was using acetylene (C2H2) in addition to N2 in a Si HiPIMS process and the other was co-sputtering of Si and C, using HiPIMS for Si and direct current magnetron sputtering (DCMS) for graphite targets in an Ar/N2 atmosphere. Langmuir probe measurements were carried out for the silicon nitride and silicon oxynitride processes and positive ion mass spectrometry for the silicon nitride processes to gain further understanding on the plasma conditions during film growth. The target current and voltage waveforms of the reactive HiPIMS processes were evaluated. The main deposition parameter affecting the nitrogen concentration of silicon nitride films was found to be the nitrogen content in the plasma. Films with nitrogen contents of 50 at.% were deposited at N2/Ar flow ratios of 0.3 and above. These films showed Si-N as the dominating component in Si 2p X-ray photoelectron spectroscopy (XPS) core level spectra and Si–Si bonds were absent. The substrate temperature and target power were found to affect the nitrogen content to a lower extent. The residual stress and hardness of the films were found to increase with the film nitrogen content. Another factors influencing the coating stress were the process pressure, negative substrate bias, substrate temperature, and HiPIMS pulse energy. Silicon nitride coatings with good adhesion and low levels of compressive residual stress were grown by using a pressure of 600 mPa, a substrate temperature below 200 °C, pulse energies below 2.5 Ws, and negative bias voltages up to 100 V. The elemental composition of silicon oxynitride films was shown to depend on the target power settings as well as on the nitrous oxide flow rate. Silicon oxide-like films were synthesized under poisoned target surface conditions, whereas films deposited in the transition regime between poisoned and metallic conditions showed higher nitrogen concentrations. The nitrogen content of the films deposited in the transition region was controlled by the applied gas flow rate. The applied target power did not affect the nitrogen concentration in the transition regime, while the oxygen content increased at decreasing target powers. The chemical composition of the films was shown to range from silicon-rich to effectively stoichiometric silicon oxynitrides, where no Si–Si contributions were found in the XPS Si 2p core level spectra. The film optical properties, namely the refractive index and extinction coefficient, were shown to depend on the film chemical bonding, with the stoichiometric films displaying optical properties falling between those of silicon oxide and silicon nitride. The properties of silicon carbonitride films were greatly influenced by the synthesis method. The films deposited by HiPIMS using acetylene as the carbon source showed silicon nitride-like mechanical properties, such as a hardness of ~ 20 GPa and compressive residual stresses of 1.7 – 1.9 GPa, up to film carbon contents of 30 at.%. At larger film carbon contents the films had increasingly amorphous carbon-like properties, such as densities below 2 g/cm3 and hardnesses below 10 GPa. The films with more than 30 at.% carbon also showed columnar morphologies in cross-sectional scanning electron microscopy, whereas films with lower carbon content showed dense morphologies. Due to the use of acetylene the carbonitride films contained hydrogen, up to ~ 15 at.%. The co-sputtered silicon carbonitride films showed a layered SiNx/CNx structure. The hardness of these films increased with the film carbon content, reaching a maximum of 18 GPa at a film carbon content of 12 at.%. Comparatively hard and low stressed films were grown by co-sputtering using a C target power of 1200 W for a C content around 12 at.%, a negative substrate bias less than 100 V, and a substrate temperature up to 340 °C.
Author: Qiliang Li
Publisher: MDPI
ISBN: 3039212257
Category : Technology & Engineering
Languages : en
Pages : 242
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Book Description
As CMOS scaling is approaching the fundamental physical limits, a wide range of new nanoelectronic materials and devices have been proposed and explored to extend and/or replace the current electronic devices and circuits so as to maintain progress with respect to speed and integration density. The major limitations, including low carrier mobility, degraded subthreshold slope, and heat dissipation, have become more challenging to address as the size of silicon-based metal oxide semiconductor field effect transistors (MOSFETs) has decreased to nanometers, while device integration density has increased. This book aims to present technical approaches that address the need for new nanoelectronic materials and devices. The focus is on new concepts and knowledge in nanoscience and nanotechnology for applications in logic, memory, sensors, photonics, and renewable energy. This research on nanoelectronic materials and devices will be instructive in finding solutions to address the challenges of current electronics in switching speed, power consumption, and heat dissipation and will be of great interest to academic society and the industry.
Author: Kompa, Günter
Publisher: kassel university press GmbH
ISBN: 3862195414
Category : Compound semiconductors
Languages : en
Pages : 762
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Book Description
Trapping effects in III-V devices pose a great challenge to any microwave device modeler. Understanding their physical origins is of prime importance to create physics-related reliable device models. The treatment of trapping phenomena is commonly beyond the classical higher-education level of communication engineers. This book provides any basic material needed to understand trapping effects occurring primarily in GaAs and GaN power HEMT devices. As the text material covers interdisciplinary topics such as crystal defects and localized charges, trap centers and trap dynamics, deep-level transient spectroscopy, and trap centers in passivation layers, the book will be of interest to graduate students of electrical engineering, communication engineering, and physics as well as materials, device, and circuit engineers in research and industry.
Author:
Publisher:
ISBN:
Category : Chemistry
Languages : en
Pages : 2540
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Author: Feng Gao (Ph. D.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 121
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Book Description
AlGaN/GaN high electron mobility transistors (HEMTs) constitute a new generation of transistors with excellent electrical characteristics and great potential to replace silicon technology in the future, especially in high power and high frequency applications. However, the poor long term reliability of these devices is an important bottleneck for their wide market insertion and limits their advanced development. This thesis tackles this problem by focusing on understanding the physics behind various degradation modes and providing new quantitative models to explain these mechanisms. The first part of the thesis, Chapters 2 and 3, reports studies of the origin of permanent structural and electrical degradation in AlGaN/GaN HEMTs. Hydroxyl groups (OH-) from the environment and/or adsorbed water on the III-N surface are found to play an important role in the formation of surface pits during the OFF-state electrical stress. The mechanism of this water-related structural degradation is explained by an electrochemical cell formed at the gate edge where gate metal, the II-N surface and the passivation layer meet. Moreover, the permanent decrease of the drain current is directly linked with the formation of the surface pits, while the permanent increase of the gate current is found to be uncorrelated with the structural degradation. The second part of the thesis, Chapters 4 and 5, identifies water-related redox couples in ambient air as important sources of dynamic on-resistance and drain current collapse in AlGaN/GaN HEMTs. Through in-situ X-ray photoelectron spectroscopy (XPS), direct signature of the water-related species is found at the AlGaN surface at room temperature. It is also found that these species, as well as the current collapse, can be thermally removed above 200 °C in vacuum conditions. An electron trapping mechanism based on H2O/H2 and H2O/O2 redox couples is proposed to explain the 0.5 eV energy level commonly attributed to surface trapping states. Moreover, the role of silicon nitride passivation in successfully removing current collapse in these devices is explained by blocking the water molecules away from the AlGaN surface. Finally, fluorocarbon, a highly hydrophobic material, is proven to be an excellent passivation to overcome transient degradation mechanisms in AlGaN/GaN HEMTs.
Author: Matteo Meneghini
Publisher: Springer
ISBN: 3319431994
Category : Technology & Engineering
Languages : en
Pages : 383
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Book Description
This book presents the first comprehensive overview of the properties and fabrication methods of GaN-based power transistors, with contributions from the most active research groups in the field. It describes how gallium nitride has emerged as an excellent material for the fabrication of power transistors; thanks to the high energy gap, high breakdown field, and saturation velocity of GaN, these devices can reach breakdown voltages beyond the kV range, and very high switching frequencies, thus being suitable for application in power conversion systems. Based on GaN, switching-mode power converters with efficiency in excess of 99 % have been already demonstrated, thus clearing the way for massive adoption of GaN transistors in the power conversion market. This is expected to have important advantages at both the environmental and economic level, since power conversion losses account for 10 % of global electricity consumption. The first part of the book describes the properties and advantages of gallium nitride compared to conventional semiconductor materials. The second part of the book describes the techniques used for device fabrication, and the methods for GaN-on-Silicon mass production. Specific attention is paid to the three most advanced device structures: lateral transistors, vertical power devices, and nanowire-based HEMTs. Other relevant topics covered by the book are the strategies for normally-off operation, and the problems related to device reliability. The last chapter reviews the switching characteristics of GaN HEMTs based on a systems level approach. This book is a unique reference for people working in the materials, device and power electronics fields; it provides interdisciplinary information on material growth, device fabrication, reliability issues and circuit-level switching investigation.
Author: JEFFREY L. DUPUIE
Publisher:
ISBN:
Category :
Languages : en
Pages : 396
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deposition scheme holds much promise for low temperature film growth.
Author: Sameer Jayanta Joglekar
Publisher:
ISBN:
Category :
Languages : en
Pages : 161
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Book Description
Gallium Nitride (GaN) belongs to a class of materials called wide band-gap semiconductors. In recent years, the versatile nature of this material has been exploited for a wide range of applications from solid state lighting to RF and microwave communication, as well as high power switching. The first part of this thesis discusses planar AlGaN/GaN transistors. GaN is a piezoelectric material, and changes in mechanical stress result in a change in the charge density which in turn affects the maximum current in AlGaN/GaN transistors. Finite element modelling techniques were applied to quantify the mechanical stress distribution in planar AlGaN/GaN RF transistors resulting from device fabrication, and operation in the on- and off-state. Thereafter, two important surface and interface effects were studied in this thesis. In the first one, the impact of surface cleanings, surface treatments and plasma-based dry etch conditions on two different types of ohmic contact technologies was investigated. Contact resistance measurements were correlated with surface characterization results. The second was that of interface positive charges at the Al2O3-GaN interface and the increase in electron density in the device resulting from them. In both these problems, a combination of device electrical measurements and material characterization techniques was used to establish direct correlations between device behavior and material properties. The second part of the thesis deals exclusively with nano-ribbon (NR) or fin-like AlGaN/GaN transistors. Fundamental transport properties of charge density and mobility in NR devices were studied in order to understand the difference in behavior of these devices from planar devices. The influence of passivation films on the charge density in these structures was investigated, using Al2O3 passivation as a specific example. Electron mobility degradation due to sidewall-scattering in NR devices was quantified using different mobility extraction methods based on device measurements. The thesis concludes with a potential application of NR AlGaN/GaN transistors for high linearity power amplification. A new kind of transistor with varying threshold voltages along the gate width is proposed to improve the DC and RF linearity of GaN-based devices.
