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GATE STACK AND CHANNEL ENGINEERING:STUDY OF METAL GATES AND GERMANIUM CHANNEL DEVICES
Title
GATE STACK AND CHANNEL ENGINEERING:STUDY OF METAL GATES AND GERMANIUM CHANNEL DEVICES.
Creator
Todi, Ravi, Sundaram, Kalpathy, University of Central Florida
Abstract / Description
The continued scaling of device dimensions in complementary metal oxide semiconductor (CMOS) technology within the sub-100 nm region requires an alternative high dielectric constant (high-κ) oxide layer to counter high tunneling leakage currents, a metallic gate electrode to address polysilicon depletion, boron penetration and high polysilicon sheet resistance, and high mobility channel materials to boost the CMOS performance. Metal gates can also offer improved thermal and chemical...
Show moreThe continued scaling of device dimensions in complementary metal oxide semiconductor (CMOS) technology within the sub-100 nm region requires an alternative high dielectric constant (high-κ) oxide layer to counter high tunneling leakage currents, a metallic gate electrode to address polysilicon depletion, boron penetration and high polysilicon sheet resistance, and high mobility channel materials to boost the CMOS performance. Metal gates can also offer improved thermal and chemical stability, but their use requires that we improve our understanding of how the metal alloy phase, crystallographic orientation, and composition affect the electronic properties of the metal alloy-oxide interface. To replace n++ and p++ polysilicon gate electrodes and maintain scaled device performance requires metal gate electrodes with work functions within 0.2 eV of the silicon conduction and valence band edges, i.e., 5.0-5.2 and 4.1-4.3 eV, for PMOS and NMOS devices, respectively. In addition to work function and thermal/chemical stability, metal gates must be integrated into the CMOS process flow. It is the aim of this work to significantly expand our knowledge base in alloys for dual metal gates by carrying out detailed electrical and materials studies of the binary alloy systems of Ru with p-type metal Pt. Three n-type metals systems, Ru-Ta, Ru-Hf and Ru-Nb have also been partially investigated. This work also focuses on high mobility Ge p-MOSFETs for improved CMOS performance. DC magnetron sputtering has been used to deposit binary alloy films on thermally grown SiO2. The composition of the alloy films have been determined by Rutherford backscattering spectrometry and the identification of phases present have been made using x-ray and electron diffraction of samples. The microstructure of the phases of interest has been examined in the transmission electron microscope and film texture was characterized via x-ray diffraction. The electrical characterization includes basic resistivity measurements, and work function extraction. The work function has been determined from MOS capacitor and Schottky diodes. The need for electron and hole mobility enhancement and the progress in the development of high-κ gate stacks, has lead to renewed interest in Ge MOSFETs. The p-MOS mobility data for Ge channel devices have been reported. The results indicate greater than 2 x improvements in device mobility as compared to standard Si device. A low frequency noise assessment of silicon passivated Ge p-MOSFETs with a TiN/TaN/HfO2 gate stack has been made. For the first time we also report results on low frequency noise characterisation for a Ge P+- n junctions with and without Ni germanidation.
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Date Issued
2007
Identifier
CFE0001554, ucf:47122
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001554
INVESTIGATIONS ON RF SPUTTER DEPOSITED SICN THIN FILMS FOR MEMS APPLICATIONS
Title
INVESTIGATIONS ON RF SPUTTER DEPOSITED SICN THIN FILMS FOR MEMS APPLICATIONS.
Creator
Todi, Ravi, Coffey, Kevin, University of Central Florida
Abstract / Description
With the rapid increase in miniaturization of mechanical components, the need for a hard, protective coatings is of great importance. In this study we investigate some of the mechanical, chemical and physical properties of the SiCN thin films. Thin films of amorphous silicon carbide nitride (a-SiCxNy) were deposited in a RF magnetron sputtering system using a powder pressed SiC target. Films with various compositions were deposited on to silicon substrate by changing the N2/Ar gas ratios...
Show moreWith the rapid increase in miniaturization of mechanical components, the need for a hard, protective coatings is of great importance. In this study we investigate some of the mechanical, chemical and physical properties of the SiCN thin films. Thin films of amorphous silicon carbide nitride (a-SiCxNy) were deposited in a RF magnetron sputtering system using a powder pressed SiC target. Films with various compositions were deposited on to silicon substrate by changing the N2/Ar gas ratios during sputtering. Nano-indentation studies were performed to investigate the mechanical properties such as hardness and reduced modulus of the SiCN films. Surface morphology of the films was characterized by using atomic force microscopy (AFM). X-ray photoelectron spectroscopy (XPS) data indicated that the chemical status is highly sensitive to the nitrogen ratios during sputtering. Further, the films were annealed in dry oxygen ambient in the temperature range of 400 – 900°C and characterized using XPS to investigate the chemical composition and oxidation kinetics at each annealing temperature. The surface roughness of these films was studied as a function of annealing temperature and film composition with the help of a "Veeco" optical profilometer. Nano-indentation studies indicated that the hardness and the reduced modulus of the film are sensitive to the N2/Ar ratio of gas flow during sputtering. AFM studies revealed that the films become smoother as the N2/Ar ratio is increased. XPS data indicated the existence of C-N phases in the as-deposited films. The study of oxidation kinetics of RF sputter deposited SiCN thin films, using XPS, suggest that N2 co-sputtering helps to suppress the formation of a surface oxide, by allowing un-bonded Si to bond with N and C inside the vacuum chamber as opposed to bonding with O in atmosphere.
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Date Issued
2005
Identifier
CFE0000839, ucf:46669
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000839