Development Of Iii V P Mosfets With High Kappa Gate Stack For Future Cmos Applications

As the semiconductor industry approaches the limits of traditional silicon CMOS scaling, introduction of performance boosters like novel materials and innovative device structures has become necessary for the future of CMOS. High mobility materials are being considered to replace Si in the channel to achieve higher drive currents and switching speeds. Ge has particularly become of great interest as a channel material, owing to its high bulk hole and electron mobilities. However, replacement of Si channel by Ge requires several critical issues to be addressed in Ge MOS technology. High quality gate dielectric for surface passivation, low parasitic source/drain resistance and performance improvement in Ge NMOS are among the major challenges in realizing Ge CMOS. Detailed characterization of gate dielectric/channel interface and a deeper understanding of mobility degradation mechanisms are needed to address the Ge NMOS performance problem and to improve PMOS performance. In the first part of this dissertation, the electrical characterization results on Ge NMOS and PMOS devices fabricated with GeON gate dielectric are presented. Carrier scattering mechanisms are studied through low temperature mobility measurements. For the first time, the effect of substrate crystallographic orientation on inversion electron and hole mobilities is investigated. Direct formation of a high-k dielectric on Ge has not given good results in the past. A good quality interface layer is required before the deposition of a high-K dielectric. In the second part of this dissertation, ozone-oxidation process is introduced to engineer Ge/insulator interface. Electrical and structural characterizations and stability analysis are carried out and high quality Ge/dielectric interface with low interface trap density is demonstrated. Detailed extraction of interface trap density distribution across the bandgap and close to band edges of Ge, using low temperature conductance and capacitance measurements is presented. Ge N-MOSFETs have exhibited poor drive currents and low mobility, as reported by several different research groups worldwide. In spite of the increasing interest in Ge, the major mechanisms behind poor Ge NMOS performance have not been completely understood yet. In the last part of this dissertation, the results on Ge NMOS devices fabricated with the ozone-oxidation and the low temperature source/drain activation processes are discussed. These devices achieve the highest electron mobility to-date, about 1.5 times the universal Si mobility. Detailed interface characterizations, trapping analyses and gated Hall device measurements are performed to identify the mechanisms behind poor Ge NMOS performance in the past.

Due to the ever increasing electric fields in scaled CMOS devices, reliability is becoming a showstopper for further scaled technology nodes. Although several groups have already demonstrated functional Si channel devices with aggressively scaled Equivalent Oxide Thickness (EOT) down to 5Å, a 10 year reliable device operation cannot be guaranteed anymore due to severe Negative Bias Temperature Instability. This book focuses on the reliability of the novel (Si)Ge channel quantum well pMOSFET technology. This technology is being considered for possible implementation in next CMOS technology nodes, thanks to its benefit in terms of carrier mobility and device threshold voltage tuning. We observe that it also opens a degree of freedom for device reliability optimization. By properly tuning the device gate stack, sufficiently reliable ultra-thin EOT devices with a 10 years lifetime at operating conditions are demonstrated. The extensive experimental datasets collected on a variety of processed 300mm wafers and presented here show the reliability improvement to be process - and architecture-independent and, as such, readily transferable to advanced device architectures as Tri-Gate (finFET) devices. We propose a physical model to understand the intrinsically superior reliability of the MOS system consisting of a Ge-based channel and a SiO2/HfO2 dielectric stack. The improved reliability properties here discussed strongly support (Si)Ge technology as a clear frontrunner for future CMOS technology nodes.

The performance and power scaling of metal-oxide-semiconductor field-effect-transistors (MOSFETs) has been historically achieved through shrinking the gate length of transistors for over three decades. As Si complementary metal-oxide-semiconductor (CMOS) scaling is approaching the physical and optical limits, the emerging technology involves new materials for the gate dielectrics and the channels as well as innovative structures. III-V materials have much higher electron mobility compared to Si, which can potentially provide better device performance. Hence, there have been tremendous research activities to explore the prospects of III-V materials for CMOS applications. Nevertheless, the key challenges for III-V MOSFETs with high-[kappa] oxides such as the lack of high quality, thermodynamically stable insulators that passivate the gate oxide/III-V interface still hinder the development of III-V MOS devices. The main focus of this dissertation is to develop the proper processes and structures for III-V MOS devices that result in good interface quality and high device performance. Firstly, fabrication processes and device structures of surface channel MOSFETs were investigated. The interface quality of In[subscript 0.53]Ga[subscript 0.47]As MOS devices was improved by developing the gate-last process with more than five times lower interface trap density (D[subscript it]) compared to the ones with the gate-first process. Furthermore, the optimum substrate structure was identified for inversion-type In[subscript 0.53]Ga[subscript 0.47]As MOSFETs by investigating the effects of channel doping concentration and thickness on device performance. With the proper process and channel structures, the first inversion-type enhancement-mode In[subscript 0.53]Ga[subscript 0.47]As MOSFETs with equivalent oxide thickness (EOT) of ~10 Å using atomic layer deposited (ALD) HfO2 gate dielectric were demonstrated. The second part of the study focuses on buried channel InGaAs MOSFETs. Buried channel InGaAs MOSFETs were fabricated to improve the channel mobility using various barriers schemes such as single InP barrier with different thicknesses and InP/InAlAs double-barrier. The impacts of different high-[kappa] dielectrics were also evaluated. It has been found that the key factors enabling mobility improvement at both peak and high-field mobility in In[subscript 0.7]Ga[subscript 0.3]As quantum-well MOSFETs with InP/InAlAs barrier-layers are 1) the epitaxial InP/InAlAs double-barrier confining carriers in the quantum-well channel and 2) good InP/Al2O3/HfO2 interface with small EOT. Record high channel mobility was achieved and subthreshold swing (SS) was greatly improved. Finally, InGaAs tunneling field-effect-transistors (TFETs), which are considered as the next-generation green transistors with ultra-low power consumption, were demonstrated with more than two times higher on-current while maintaining much smaller SS compared to the reported results. The improvements are believed to be due to using the In[subscript 0.7]Ga[subscript 0.3]As tunneling junction with a smaller bandgap and ALD HfO2 gate dielectric with a smaller EOT.

Comprehensive reference on the fundamental principles and basic physics dictating metal–oxide–semiconductor field-effect transistor (MOSFET) operation Advanced Nanoscale MOSFET Architectures provides an in-depth review of modern metal–oxide–semiconductor field-effect transistor (MOSFET) device technologies and advancements, with information on their operation, various architectures, fabrication, materials, modeling and simulation methods, circuit applications, and other aspects related to nanoscale MOSFET technology. The text begins with an introduction to the foundational technology before moving on to describe challenges associated with the scaling of nanoscale devices. Other topics covered include device physics and operation, strain engineering for highly scaled MOSFETs, tunnel FET, graphene based field effect transistors, and more. The text also compares silicon bulk and devices, nanosheet transistors and introduces low-power circuit design using advanced MOSFETs. Additional topics covered include: High-k gate dielectrics and metal gate electrodes for multi-gate MOSFETs, covering gate stack processing and metal gate modification Strain engineering in 3D complementary metal-oxide semiconductors (CMOS) and its scaling impact, and strain engineering in silicon–germanium (SiGe) FinFET and its challenges and future perspectives TCAD simulation of multi-gate MOSFET, covering model calibration and device performance for analog and RF applications Description of the design of an analog amplifier circuit using digital CMOS technology of SCL for ultra-low power VLSI applications Advanced Nanoscale MOSFET Architectures helps readers understand device physics and design of new structures and material compositions, making it an important resource for the researchers and professionals who are carrying out research in the field, along with students in related programs of study.

As scaling of silicon-based CMOS devices approaches its end, there is an ever increasing interest in high mobility materials. Among potential candidates for future CMOS devices, III-V materials are the most promising option due to their superior carrier transport properties. Despite their attractive material properties, they face several critical challenges that need to be resolved. The main limitation in III-V MOSFETs is lack of a good native oxide. Recently, devices utilizing a gate stack formed with high-[greek small letter kappa] and metal gate electrode are being explored for EOT scaling. Compared to Si MOSFETs, the surfaces of III-V channel materials are prone to deteriorate, resulting in degradation threshold voltage control, subthreshold characteristics, and overall device performance. The purpose of this dissertation is to address improvement of surface characteristics of III-V materials, especially, InGaAs. First of all, beryllium oxide (BeO) is considered as interface passivation layer for InGaAs MOSFETs. In order to apply BeO onto InGaAs, the chemical and mechanical properties are first studied. Liquid BeO precursor is never used in ALD systems. The chemical properties of ALD BeO film are revealed from AES, XPS, NRA, RBS, and REELS. Using nano-indentation, the mechanical characteristics of ALD BeO are investigated. The second part of the study focuses on the application of ALD BeO to InGaAs MOSFETs. The surface channel MOSFET is employed to understand BeO dielectric with III-V channel. The quantum well (QW) structure is known to withstand InGaAs intrinsic material properties from a device point of view. ALD BeO is applied to QW InGaAs MOSFETs as an interface passivation layer below HfO2. The impact of ALD BeO application for interface passivation is presented using the improvement in device characteristics, for example, drive current (ION), low leakage current (IOFF), effective mobility ([mu]eff), and interface trap density (Dit). The third and final part are about process research for InGaAs surface quality. III-V channel materials are inherent to create notorious native oxide that needs to be treated before the fabrication process. In order to protect pristine III-V surface, in-situ Ar treatment is studied and used before high-[greek small letter kappa] deposition. In addition, deuterium (D2) high-pressure annealing is considered to passivate III-V interface with high-[greek small letter kappa]. To demonstrate the efficacy of these treatment processes, InGaAs MOSCAPs are fabricated, and capacitance characteristics are analyzed and compared. The C-V hysteresis and multi-frequency C-V are measured, and the interface trap density (Dit) is extracted using the C-V result.

Si complementary metal-oxide-semiconductor (CMOS) technology has been prospered through continuously scaling of its feature size. As scaling is approaching its physical limitations, new materials and device structures are expected. High electron mobility III-V materials are attractive as alternative channel materials for future post-Si CMOS applications due to their outstanding transport property. High-k dielectrics/metal gate stack was applied to reduced gate leakage current and thus lower the power dissipation. Combining their benefits, great efforts have been devoted to explore III-V/high-k/metal metal-oxide-semiconductor field-effect-transistors (MOSFETs). The main challenges for III-V MOSFETs include interface issues of high-k/III-V, source and drain contact, silicon integration and reliability. A comprehensive study on III-V MOSFETs has been presented here focusing on three areas: 1) III-V/high-k/metal gate stack: material and electrical properties of various high-k dielectrics on III-V substrates have been systematically examined; 2) device architecture: device structures from planar surface channel MOSFETs and buried channel quantum well FETs (QWFETs) to 3D gate-wrapped-around FETs (GWAFETs) and tunneling FETs (TFETs) have been designed and analyzed; 3) fabrication process: process flow has been set up and optimized to build scaled planar and 3D devices with feature size down to 40nm. Potential of high performances have been demonstrated using novel III-V/high-k devices. Effective channel mobility was significantly improved by applying buried channel QWFET structure. Short channel effect control for sub-100nm devices was enhanced by shrinking gate dielectrics, reducing channel thickness and moving from 2D planar to 3D GWAFET structure. InGaAs TFETs have also been developed for ultra-low power application. This research work demonstrates that III-V/high-k/metal MOSFETs with superior device performances are promising candidates for future ultimately scaled logic devices.

This book contains 35 review articles on nanoscience and nanotechnology that were first published in Nature Nanotechnology, Nature Materials and a number of other Nature journals. The articles are all written by leading authorities in their field and cover a wide range of areas in nanoscience and technology, from basic research (such as single-molecule devices and new materials) through to applications (in, for example, nanomedicine and data storage).