bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical Properties of III-V/Oxide Interfaces
Authors: Brammertz Guy , Lin H.C. , Martens Koen , Alian Ali-Reza , Merckling C. , Penaud Julien , Kohen David , Wang W.-E , Sioncke S. , Delabie A. , Meuris Marc , Caymax Matty R. , Heyns Marc
Published: May 2009

We present the interface state distribution at GaAs-oxide interfaces, which consist of two large peaks around mid-gap energies, one donor-like and one acceptor-like, as well as two smaller peaks closer to the band-edge energies, which are responsible for room temperature frequency dispersion in CV-curves. The latter two peaks are strongly reduced by S-passivation treatments as well as forming gas anneals, whereas the mid-gap peaks do not get affected by such treatments. It is argued that the large midgap peaks are likely caused by physical relaxation of the surface due to stress created by the oxidation, with creation of large densities (~1013 cm-2) of As and Ga vacancies at the GaAs surface. The interface state distribution of In0.53Ga0.47As-oxide interfaces is presented as well, which consists of two donor-like peaks, one large peak close to (and partly in) the valence band edge and one smaller peak around mid-gap energies. Such an interface state distribution explains the results obtained by In0.53Ga0.47As-based nMOSFET devices. Here, again, it is argued that these two peaks are likely proper to the In0.53Ga0.47As surface itself, and due to the presence of a large density of vacancies at the surface.
Surface Studies of III-V Materials: Oxidation Control and Device Implications
Authors: Hinkle Christopher , Milojevic Marko , Sonnet Arif , Kim Hyunchul , Kim Jiyoung , Vogel Eric M. , Wallace Robert M.
Published: May 2009

Despite the long history of research on III-V semiconductor materials, the determination and control of the individual oxidation states of these substrates is still poorly understood. In this study, multiple surface treatments have been employed to determine the presence and concentration of the individual oxidation states of both As and Ga. The removal of these surface oxides is demonstrated through particular techniques. It is established that not all of these oxidation states are of poor electrical quality, while eliminating the presence of certain oxidation states results in a marked improvement in MOS device performance.
Effect of the Flat and Pattern Surface Texturing on Light Extraction of GaN Flip-Chip Light-Emitting Diodes
Authors: Horng Ray-Hua , Liao Zi-Wei , Tsai Yu-Li , Hu Hung Lieh , Tsai Yao-Jun , Hsu Chen-Peng , Chu Mu-Tao
Published: May 2009

Device performances of GaN-based flip-chip light-emitting diodes (FC LEDs) with planar and patterned sapphire substrates (PSS) were compared in this study. It was found that for the FC LED with planar sapphire, enhancement factor of luminous intensity can be raised to 107.5% after the processes of substrate removal and surface roughening. By contrast, for the FC LED with PSS, the intensity enhancement factor is already up to 169.5% without any post-processes as compared with the intensity of an as-fabricated conventional FC LED. Further intensity improvement to 205.1% can be achieved for the FC LED with PSS by employing subsequent processes such as substrate removal and surface roughening. These results indicate that the PSS approach is useful in improving light extraction of a nitride-based FC LED.
III-V Semiconductors, a History in RF Applications
Authors: Barratt Curtis A.
Published: May 2009

The history of III-V semiconductors in RF applications is more than forty years long. It began in epitaxially prepared diodes based on unique physical properties for certain applications including the "Gunn" effect as well as the higher mobility of an electron when compared with silicon. This gave way to planar processing and ion implantation which permitted the realization of the monolithic microwave integrated circuits (MMICs). Digital wireless applications have become the most ubiquitous applications for III-V RF devices. This was facilitated by taking advantage of not simply the mobility advantages of III-V semiconductors but also the unique properties available through the use of different combinations of active layer alloy compositions. This has driven wide market acceptance for pHEMT and HBT based electronics used in every day life.
Photoelectrochemical Splitting of Water to H2 and O2 at n-Fe2O3 Nanowires and Nanocrystalline Carbon-Modified (CM)-n-Fe2O3 Thin Films
Authors: Frites Mourad , Khan Shahed U.
Published: May 2009

Iron oxide n-Fe2O3 nanowire thin films were synthesized by thermal oxidation of Fe metal sheet (Alfa Co. 0.25 mm thick) in an electric oven then tested for their photoactivity. The photoresponse of the n-Fe2O3 nanowires was evaluated by measuring the rate of water splitting reaction to hydrogen and oxygen, which was found to be proportional to photocurrent density, jp. The optimized electric oven-made n-Fe2O3 photoelectrodes showed photocurrent densities of 1.32 mA cm-2 at measured potential of 0.0 V/SCE with photoconversion efficiency of 1.69 % at applied potential of 0.70 V vs Eaoc (electrode potential at open circuit conditions) under illumination intensity of 100 mW cm-2 from a Solar simulator with a global AM 1.5 filter. The photoactivity was improved upon incorporation of carbon into the lattice of n-Fe2O3 by flame oxidation at 850{degree sign}C. The carbon modified (CM)-n-Fe2O3 showed enhanced photocurrent response to 3.14 mA cm-2 at a measured potential of 0.0 V/SCE with an efficiency of 2.23% at applied potential of 0.52 V vs Eaoc. The nanocrystalline CM-n- Fe2O3 and n-Fe2O3 nanowires thin films were characterized using photocurrent density measurements under monochromatic light illumination, UV-Vis spectra, X-ray diffraction (XRD) and scanning electron microscopy (SEM).
Hydrothermally Grown ZnO Nanorods as Cell Adhesion Control Coating for Implant Devices
Authors: Chu Byung Hwan , Chang C.Y. , Leu L.C. , Norton David , Lee Jiyeon , Lele T.P. , Jiang Peng , Tseng Y. , Pearton Stephen J. , Gupte Anand , Keselowsky B. , Ren F
Published: May 2009

Recent studies show that hydrothermally grown ZnO nanorods can modulate cell adhesion and survival on various substrates. Hydrothermal growth of ZnO nanorods on biliary stents and nitinol wires used in metal stents is demonstrated. The nanorods can be conformably coated with silicon dioxide using low temperature plasma enhanced chemical vapor deposition (PECVD) system to reduce immunogenic response. In addition, the control of nanorod density is demonstrated by using a surfactant, Triton X-100. These results show promise of using nanorod array to control cell adhesion and viability on implantable devices.
Observation of Self-limiting Regime in the Atomic Layer Deposition of ZnO Films using Nitrous Oxide as the Oxygen Supply
Authors: Chung Ping-Han , Lai Hung-Wei , Lin Yen-Ting , Yen Kuo-Yi , Kung Chung-Yuan , Gong Jyh-Rong
Published: May 2009

We report the observation of self-limiting process in the atomic layer deposition (ALD) of zinc oxide (ZnO) films on (0001) sapphire substrates at low temperatures using diethylzinc (DeZn) and nitrous oxide (N2O). I was found that a monolayer-by- monolayer growth regime occurred in a range of DeZn flow rates from 5.7 to 8.7 μmole/min. Furthermore, the temperature window for the self-limiting process of the ALD-grown ZnO films was also observed ranging from 290 to 310 °. The transmission and absorption spectra of the ZnO films prepared in the self-limiting regime show good optical characteristics with tramsmittance being more than 80% in the visible light region. Experimental results indicate that ZnO films grown in the self-limitng regime all exhibit improved materials characteristics and thickness uniformity.
Electrochemical Growth Gold Buffer Layer on H-Si(111) Surfaces and Their Applications
Authors: Allongue Philippe , Maroun Fouad , Jurca Hugo , Cortes Robert , Prod'homme Patricia , Tournerie Nicolas
Published: May 2009

This paper reviews our recent work about gold electrodeposition on H-terminated Si(111). It is shown that Au(111)/Si(111) epitaxial layers are grown and that the film morphology can be varied according to the deposition conditions (potential and solution pH). At pH = 14 (cyanide solution) selective gold nucleation at the substrate monatomic step edges is observed. A homogeneous nucleation is obtained at pH 4 (chloride solution). In the former case 3D growth occurs and in the latter case ultra smooth buffer layers are obtained. Application of these substrates to formation of magnetic nanostructures with tuneable properties is demonstrated.
Characterisation of Self-Assembled Monolayers on Germanium Surfaces via NEXAFS
Authors: Lommel Martin , Reinhardt Falk , Kolbe Michael , Beckhoff Burkhard , Müller Matthias , Hönicke Philipp , Kolbesen Bernd
Published: May 2009

The formation of self-assembled monolayers (SAMs) by suitable organic molecules with appropriate anchor groups on semiconductor surfaces may be used either to probe both the chemical state and the quality of the surface or to achieve surface passivation. Molecules with thiol anchor groups are able to bond to hydrogen-terminated germanium surfaces (Ge-S bond). We have prepared SAMs of alkylthiols with trifluoroacetate head groups on germanium. The germanium surface prior to and after SAMs formation has been characterised by Near-Edge X-Ray Absorption Fine Structure spectroscopy (NEXAFS) with synchrotron radiation in the PTB laboratory at BESSY II. We succeeded in assigning S-NEXAFS peaks to the Ge-S bond formed during self-assembly and were able to distinguish between different fluorine species via F-NEXAFS.
Electrochemical Stability of a Novel Inorganic Protective and Functionalizable Monolayer onto InP
Authors: El Ali Oula , Goncalves Anne-Marie , Mezailles Nicolas , Mathieu Charles , Le Floch Pascal , Etcheberry Arnaud
Published: May 2009

A new route of InP passivation was clearly ruled by an anodic electrochemical process in liquid ammonia as a relevant nonaqueous solvent. The coupling approach using both galvanostatic control and XPS analyses evidenced that this first protective film upon InP was definitely associated to one coating monolayer of general formula [ (H2N)P=N-]n. The electrochemical stability of the complete covering thin film was tested during hydrogen evolution in HCl aqueous solution. In spite of the high cathodic charge, unexpectedly no cathodic decomposition of the coated InP semiconductor was detected by XPS analyses. The electrical conductivity of this protective film and its electrochemical stability under negative overvoltage was then reported. In contrast to a bare InP, the electroless immersion of the protected InP in K2PtCl4 solution did not lead to the formation of metallic Pt cluster onto the substrate. On the contrary, the presence of amino groups in the film offered a unique opportunity for Pt (+II) grafting. A hybrid inorganic structure was proposed from the N/Pt atomic surface ratio, slightly higher than 2.0. The stability of the covered InP substrate as well as the ultra thin passivated film upon functionalization were also demonstrated from XPS analyses.
Morphology, Composition and Electrical properties of Thin Anodic Oxides on InP
Authors: Simon Nathalie , Decorse Pascanut Claudia , Santinacci Lionel , Goncalves Anne-Marie , Joudrier Anne-Laure , Etcheberry Arnaud
Published: May 2009

Depending on the applied electrochemical parameters, various anodic films can be grown onto InP in aqueous media. In borate buffer at pH = 9, the formation of homogeneous and thin InPO4-like films occurred when anodic treatment is performed with a low current density, while with higher imposed current configuration porous and thicker layers are grown. In this work, AFM measurements coupled with XPS analyses and capacitance-voltage investigations have been used to study the relationship between morphology, composition and electrical properties of different anodic oxide films performed on InP surface, with current densities ranging from 1 mA.cm-2 to 100 mA.cm-2.
Simulating Crystallographic Pore Growth on III-V Semiconductors
Authors: Leisner Malte , Carstensen Jürgen , Föll Helmut
Published: May 2009

In this work, the growth of crystallographically oriented pores in III-V semiconductors has been investigated. Based on new and previous results a model for pore growth has been developed, which is mainly based on a stochastic branching probability of the pores. The stochastic nature of the model allowed to implement it as the core for Monte-Carlo-Simulations of pore growth. The simulations were able to reproduce the main features of crystallographically oriented pores, like uniform pore growth in n-type InP or the formation of domains on n-type GaAs and InP. The model is also capable of reproducing the logarithmic growth law for the pore depth, as well as the pore density oscillations with depth, as recently found.
Production of High Aspect Ratio Single Holes in Semiconductors
Authors: Gerngroß Mark-Daniel , Föll Helmut , Cojocaru Ala , Carstensen Jürgen
Published: May 2009

In many areas of research exists a need for single small holes with diameters from a few nm to several µm and large aspect ratios. Ex-isting technologies for that are complex and rather limited. It is shown by a simple proof of principle that suitable single holes or specific arrays of some single holes can be made by first etching a very large number of small and deep holes or pores into semicon-ductors like Si or InP by established electrochemical means, fol-lowed by masking the desired holes and filling all others with, e.g., a metal in a galvanic process. The potential and limitations of this technique are discussed in some detail.
Surface Chemistry and Nanotopography of Step-Bunched Silicon Surfaces: in-system SRPES and SPM Investigations
Authors: Stempel Thomas , Munoz Andres , Skorupska Katarzyna , Lublow Michael , Kanis Michael , Lewerenz H. J.
Published: May 2009

The formation of step bunching was observed by atomic force microscopy on n-type Si(111) surfaces during the electrodeposition of noble metals under semiconductor depletion conditions. The surface chemical analysis performed by synchrotron radiation photoelectron spectroscopy (SRPES) indicates the formation of an ultra-thin oxide film along with the topological transformation. Step bunching is interpreted in terms of site-specific etching controlled by the reactivity of kink sites and step edges together with the surface accumulation of holes supplied by the reduction of Pt-chloride complexes via the valence band.
The Influence of Thermal Treatment on the Electronic Properties of a-Nb2O5
Authors: La Mantia Fabio , Santamaria Monica , Habazaki Hiroki , Di Quarto Francesco
Published: May 2009

The effect of thermal treatments for 1h at 250{degree sign}C in air or under vacuum on the electronic structure of thick amorphous anodic niobia was characterized by electrochemical impedance, differential admittance (DA) and photocurrent spectroscopy (PCS). The analysis of anodized niobia has revealed that it behaves as a pure dielectric. The thermal treatment in air increases the value of the differential capacitance of the niobia sample. The effect is stronger when the thermal treatment is carried out in vacuum and can be cancelled out by reanodizing the oxide to the initial formation potential. In the case of thermally vacuum-treated sample, a behavior typical of semiconducting amorphous material has been revealed at different frequencies. The PCS measurements were used to derive the optical band gap value of niobia sample and to confirm the location of the flat band potential derived from admittance data.
Positive and Negative Oxygen Vacancies in Amorphous Silica
Authors: Kimmel Anna , Sushko Peter , Shluger Alexander , Bersuker Gennadi
Published: May 2009

We modeled all stable positive and negative charge states of oxygen vacancies originating from the neutral O3≡Si=Si≡O3 defect in amorphous SiO2 (a-SiO2) using an embedded cluster method on a distribution of structural sites. For the first time, we predict the geometry, electronic structure and spectroscopic properties of doubly ionized and negatively charged oxygen vacancies in a-SiO2 and demonstrate that negatively charged vacancies serve as deep electron traps. The results demonstrate that oxygen vacancies can be responsible for both the electron and hole trapping in silica. We compare our findings with the previous calculations and with the recent experimental data.
Interfacial Control and Electrical Properties of Ge MOS structures
Authors: Takagi Shinichi , Taoka Noriyuki , Takenaka Mitsuru
Published: May 2009

Ge MOSFETs have generated a strong interest as a current drive enhancement technology beyond strained-Si technologies. The key technologies for realizing Ge MOSFETs are the formation of superior MOS interfaces. However, control technologies of to provide superior Ge MOS/MIS interfaces has not been fully established yet. In this report we review recent technologies for controlling Ge MOS interfaces. In particular, we report the interface properties of thermally-oxidized GeO2/Ge and Si-passivated GeO2 interfaces in detail. In addition, we introduce a new measurement method for studying the physical origin of low current drive in Ge n-MOSFETs, where electron and hole mobility of SiO2/Ge interfaces are evaluated for an identical MOS interface by using metal source/drain GOI MOSFETs with a Kelvin pattern.
Control of Properties of GeO2 Films and Ge/GeO2 Interfaces by the Suppression of GeO Volatilization
Authors: Kita Koji , Lee Choong Hyun , Nishimura Tomonori , Nagashio Kosuke , Toriumi Akira
Published: May 2009

Control of both GeO2 film quality and GeO2/Ge interface properties were successfully demonstrated, based on the understanding of GeO kinetic behaviors in GeO2/Ge stacks. The GeO volatilization was driven by GeO generation at GeO2/Ge interface, but the volatilization rate was limited by GeO diffusion process in GeO2 film. It was found that the gap states in GeO2 films induced by GeO volatilization were detectable as a sub-gap photo-absorption by spectroscopic ellipsometry. We have successfully demonstrated two approaches to control the GeO volatilization: the cap layer introduction and the annealing in high-pressure O2 ambient. The characteristics of Ge MOS capacitors were significantly improved by both of those two approaches. In addition, a Ge MOSFET fabricated with GeO2, thermally grown in high-pressure O2 ambient, showed a relatively high electron mobility.
Design of High-k Interfacial Layer Formation by Cycle-by-Cycle Deposition and Annealing Method
Authors: Ogawa Arito , Iwamoto Kunihiko , Ota Hiroyuki , Takahashi Masashi , Hirano Akito , Nabatame Toshihide , Toriumi Akira
Published: May 2009

We have developed a process for forming an ultra-thin high-k interfacial layer (HfSiOx-IL or AlSiOx-IL) for high-k gate stacks. The HfSiOx-IL and AlSiOx-IL was grown by Cycle-by-Cycle Deposition & Annealing method (this method is called CC-D&A, and the IL deposited by this method is called CC-IL). This method utilizes the solid-phase reaction between high-k films (HfO2 or Al2O3) and Si-substrate performed by repeating the sequence of 1 cycle ALD HfO2 (or Al2O3) deposition and RTA. The CC-IL enables the formation of very uniform films consisting of a few mono-layers. In this paper, we demonstrated the physical properties for CC-IL, and electrical properties for high-k gate stacks with CC-IL, and we achieved 0.5nm-EOT high-k gate stacks of CMOS with gate-first process.
Multi-Vibrational Hydrogen Release: A Dielectric Breakdown Model for Ultra-thin SiO2/SiON and High-K Stack
Authors: Ribes Guillaume C. , Mora Pascal , Roy D.
Published: May 2009

In this paper we propose a review of the model called MVHR (Multi-Vibrational Hydrogen Release) dealing with Si-H bond physics and allowing explaining the complex physics of gate oxide breakdown. A large amount of effect as polarization, gate bias, temperature, and oxide thickness impacts are well explained by this physical model. In addition the model predicts some process related effects such as poly doping and oxide nitridation impact. The application of this model to high-K metal gate stack is discussed and a complete description of physical degradation in high-K stack is provided. A large amount of gate stack is studied as gate material (TiN, TaC, Poly), gate oxide (SiON, HfSiON, HfO2, HfZrO2). Hence the reliability limit of the SiON gate oxide will be predicted and guideline will be provided for metal gate dielectrics lifetime extrapolation.
New Insights of BTI Degradation in MOSFETs with SiON Gate Dielectrics
Authors: Li Ming-Fu , Huang D.M , Liu W.J , Liu Z.Y , Huang X. Y.
Published: May 2009

It is widely recognized that recovery during measurement delay seriously misleads the BTI phenomena. We have developed a modified Charge Pumping (MCP) method to measure the interface trap generation under stress with negligible recovery during measurement delay. The method simply extends the inversion level Vinv of the CP pulse to the stress voltage and keeps the duty cycle of Vinv as large as possible, therefore the stress is almost "on" during measurement. For the first time, we developed a diagram representation of CP process and used to the physical analysis for the contribution and exclusion of slow oxide charge contribution in the CP current of this MCP method. Using this MCP method and the fast pulsed Id-Vg method (FPM) we developed in the past, we systematically investigate and compare the NBTI degradation of p-MOSFETs with thermal (TNO) and plasma (PNO) nitrided SiON gate dielectrics with the same nitrogen surface concentration. We also systematically measure the interface trap degradations in four configurations of NBTI and PBTI stresses for both n-MOSFETs and p-MOSFETs. The following results are achieved: (1) The oxide charge induced degradation in TNO SiON devices is several times larger than those in PNO devices under the same stress condition, due to the larger charge moment in the gate dielectrics of the TNO devices. (2)
Different Types of Degradation and Recovery Mechanisms on NBT Stress for Thin SIO2 Films by On-The-Fly Measurement
Authors: Teramoto Akinobu , Kuroda Rihito , Suko Tomohiro , Sato Masaki , Tsuboi Takashi , Sugawa Shigetoshi , Ohmi Tadahiro
Published: May 2009

We demonstrate NBTI characteristics induced by the conventional high voltage and the hole injection stresses using an On-the-Fly measurement technique. In the case of the conventional stress, the recovery rate just after the stress is much larger than that of the hole injection stress in which stress gate bias voltage is same as the operation condition. The recovery rate of conventional stress becomes same as that of the high hole injection stress but it is still larger than that of the low hole injection stress. It is considered that the conventional stress causes the excess trap occupation and the different degradation from the operation condition. The low hole injection under the same gate voltage as the operation condition causes the same degradation and recovery mechanisms as operation condition. An accurate NBTI lifetime prediction based on the gate voltage acceleration stress is very difficult especially when using the On-the-Fly characterization method.
Impact of Sensing Gate Bias on NBTI of Hf-based Dielectric Stacks
Authors: Ji Zhigang , Lin Lin , Zhang Jian
Published: May 2009

The negative bias temperature instability (NBTI) is limiting the lifetime of pMOSFETs with SiON gate dielectric and it is generally believed that Hf-based dielectric stack has higher instability than SiON. As Hf-based dielectric stacks are replacing SiON, there is a pressing need for characterizing their NBTI. Traditionally, the threshold voltage instability, ΔVth, is evaluated with a sensing gate bias, Vgsense, close to Vth. Vth is lower than the digital circuit operation bias and the implicit assumption is that ΔVth is independent of Vgsense. This work will show that ΔVth for Hf-based stacks increases substantially when Vgsense rises from Vth to the operation level. This Vgsense effect should be taken into account when modeling the impact of NBTI on circuit operation in the future.
The Influence of Oxide Charge on Carrier Mobility in HfO2/TiN Gate Silicon MOSFETs
Authors: Hurley Paul K. , Negara Adi , Van Hemert Tom , Cherkaoui Karim
Published: May 2009

In this work we will provide the results of an investigation into electron and hole mobility at high inversion charge density (6 to 8x1012 cm-2) in TiN/HfO2/SiOx/Si MOSFETs. We examine the influence of oxide charge on carrier mobility by using temperature bias stress to deliberately increase the density of oxide charge in the HfO2/SiOx gate stack. The temperature dependence of the electron mobility (50 K to 350 K) and hole mobility (218 K to 373 K) is determined before and after the various levels of oxide and interface degradation to allow an experimental determination of the Coulomb scattering term (α) as a function of temperature for various oxide charge levels. Based on the temperature dependant α determined for a 3nm HfO2 gate thickness n channel MOSFET, an empirical model has been developed which accurately predicts the measured electron mobility for the 2.4, 2.0 and 1.6nm HfO2 gate thicknesses.
2-D Roughening of SiO2 Thermally Grown on Atomically Flat Si Surface
Authors: Yamabe Kikuo , Ohsawa Keiichiro , Hayashi Yuusuke , Hasunuma Ryu
Published: May 2009

In this study, the atomic-scale roughness and uniformity of SiO2 thermally grown on atomically flat Si surface are investigated. The SiO2 surface roughness increases with increasing oxide thickness in the initial rapid oxidation region in the Deal-Grove model. This roughness growth can be related to re-oxidation of SiO emitted from the Si/SiO2 interface near the SiO2 surface. On the other hand, the roughness growth is saturated in the linear rate oxidation region. It is explained that the emitted SiOs within the SiO2 are re-oxidized and the generated oxidation stress is absorbed within the film.
Investigation of Hydrogenated Amorphous SiNx:H Films Grown by Rapid Thermal Chemical Vapor Deposition
Authors: Lai Yi-Sheng , Yung S. W.
Published: May 2009

Hydrogenated silicon nitride films were deposited with NH3, SiH4 and N2 gas mixture at 700oC by rapid thermal chemical vapor deposition (RTCVD) system. Wafer curvature measurements were carried out at room temperature to study the SiNx:H film stress with various deposition parameters. The NH3/N2 flow ratio and deposition pressure are found to influence the film stress. The stress of SiNx:H films deposited by RTCVD is tensile, which can reach ~ 1.5 GPa in our study. The influence of the reactive gas mixture and working pressure on the film stress, in connection with its material properties, is demonstrated.
Development and Characterization of High-k Gate Stack for Ge MOSFETs
Authors: Xie Ruilong , Zhu Chunxiang
Published: May 2009

Recent developed high-permitivity (high-k) materials provide another opportunity to germanium (Ge) as a channel material in metal-oxide-semiconductor field-effect transistor applications. In this paper, developments of high-k/Ge gate stack have been reviewed. Various interface engineering processes including surface passivation techniques and post-gate treatments have been discussed. Physical and electrical characterizations have been made to evaluate the performance of interface engineered Ge MOS devices.
Structural Metastability and Size Scalability of Phase-Controlled HfO2 Formed through Cap-PDA
Authors: Migita Shinji , Watanabe Yukimune , Ota Hiroyuki , Nabatame Toshihide , Toriumi Akira
Published: May 2009

Cubic phase HfO2 films are prepared by the "Cap-PDA" process, wherein amorphous HfO2 films are annealed after deposition of gate electrodes. A high dielectric constant, as large as 50, is obtained in these cubic phase HfO2 films. Through investigations of electrode materials, such as Si/TaN, Si/TiN and Si, the key material in the Cap-PDA process is found to be Si. In order to obtain a metastable cubic phase, both the initial phase of the HfO2 film before Cap-PDA and thermal management during Cap-PDA are crucial. The advantages of cubic phase HfO2 films in scaled devices are confirmed by demonstrations of sub-1 nm equivalent oxide thickness MOSCAPs and sub-100 nm gate length MOSFETs. Cubic phase HfO2 film, which yields a higher dielectric constant than other lower symmetry phases, is a strong candidate for future scaled CMOS.
Cubic Structured HfLaO Dielectrics for MIM Capacitor for RF IC Applications
Authors: Zhang Lu , He Wei , Chan Daniel , Cho Byung Jin
Published: May 2009

Metal-Insulator-Metal (MIM) capacitors with various thickness as (22 nm, 30 nm, 37 nm and 44 nm) of La (8%) doped HfO2 deposited using atomic layer deposition were fabricated. A high dielectric constant value of 38 can be obtained when 8% La doped HfO2 is crystallized into cubic structure. While amorphous HfLaO demonstrates a quadratic voltage linearity <1000 ppm/V2 up to a capacitance density of 9fF/µm2, both amorphous and crystallized HfLaO film shows good leakage current characteristics. The higher k value of HfLaO benefits MIM capacitor for RF ICs.
The Perovskite SrTiO3 on Si/SiO2 by Liquid Injection MOCVD
Authors: Dubourdieu Catherine , Salicio Olivier , Lhostis Sandrine , Auvray Laurent , Rozier Yohann , Ducroquet Frederique , Daniele Stephane
Published: May 2009

SrTiO3, which has a very high dielectric permittivity κ in the form of bulk material (κ ~ 300), has been considered as a potential candidate for the replacement of SiO2-based gate oxide in future CMOS transistors and as a promising dielectric for next generations of DRAM capacitors. Like all perovskite-type oxides, optimized properties require a stringent control of the composition and of the interfaces with the electrodes. Here, we address issues such as the stoichiometry control of the films synthesized by metal organic chemical vapor deposition and the interface engineering on Si/SiO2 through the precursor chemistry. The silicate layer formed at 700{degree sign}C can be minimized and even suppressed. The dielectric properties are discussed with respect to thickness and composition. Although the perovskite phase is obtained for a large range of Sr/Ti ratio in the films, optimal dielectric properties are obtained in a very narrow range for Sr-deficient films.
Charge Trapping Characteristics of TaYOx Gate Dielectrics on Ge under DC and AC Stressing
Authors: Mahata Chandreswar , Bera Milan K. , Mallick S. , Majhi B. , Hota M. K. , Das T. , Verma S. , Maiti C. K.
Published: May 2009

TaYOx gate dielectric has been deposited on p-Ge by RF co-sputtering of Ta2O5 and Y2O3 targets. Charge trapping/detrapping behavior of Au/TaYOx/p-Ge MIS capacitors have been studied under DC and AC stressing of different amplitudes and dynamic voltage stresses in order to study the transient response and the degradation mechanism of the dielectric. The current transients observed during dynamic voltage stress have been interpreted in terms of the charging/discharging of Ge/TaYOx interface and bulk TaYOx traps. The change in Vfb and gate current during unipolar pulse voltage stressing shows that the main degradation takes place at low frequencies. Both types of trapping are observed under dynamic stressing both with the gate and substrate injections.
Pulsed-Chemical Vapor Deposition of Ruthenium and Ruthenium Dioxide Thin Films using RuO4 Precursor for the DRAM Capacitor Electrode
Authors: Han Jeong Hwan , Lee Sang Woon , Choi Gyu Jin , Lee Sang Young , Hwang Cheol Seong , Dussarrat Christian , Gatineau Julien
Published: May 2009

Ru and RuO2 thin films were grown on Si, SiO2 and TiN substrates by pulsed chemical vapor deposition using RuO4 and 5%H2/95%N2 as the precursor and reducing gas, respectively. Ru film showed an excellent thermal stability, high growth rate of 0.18nm/pulse (0.43nm/min), low impurity concentration, conformal step coverage and very smooth surface. The TiO2 film grown on this Ru electrode showed much improved electrical performance compared to those on the other Ru electrode. RuO2 thin film can be deposited by decreasing the H2/N2 gas supply rate. RuO2 thin film has excellent conformal step coverage on a hole structure with an opening diameter of 100nm and a depth of 1000nm. With ¬RuO2 thin film as sub-electrode of MIM capacitor, the equivalent oxide thickness of TiO2 film could be decreased to 0.56nm within the specification of DRAM leakage current.
PECVD Bi-Layer ARC for BARC-less Immersion Lithography
Authors: Tang Betty , Seamons Martin , Lin Michael , Dai Huixiong , Ramirez Ricardo
Published: May 2009

A PECVD bi-layer Dielectric Anti-Reflective Coating (DARC®) process has been developed as a cost-effective solution for immersion lithography. The proposed bi-layer DARC scheme eliminates the need for a Bottom Anti-Reflective Coating (BARC) which is commonly used in both dry and immersion lithography processes, thereby reducing manufacturing cost and improving etch margin for better CD control. The bi-layer DARC film properties are highly tunable for different underlayers to provide optimal reflectivity control. With the bi-layer DARC scheme, we have demonstrated a minimum line width of 30 nm with a wider process window and comparable line edge roughness (LER) as a BARC scheme. The patterning performance is stable after multiple rework cycles and extended queue time, proving the manufacturability of the bi-layer DARC process.
Investigation of the Thin Silicon Oxide Deposited with Different Main Gases and Gap Distances of Atmospheric-pressure Plasma Jet at Low Temperature for OTFTs Gate Insulator
Authors: Chang Kow-Ming , Huang Shih-Syuan , Lin Je-Uai , Lin Chih-Hsiang
Published: May 2009

Low operation voltage organic thin film transistors (OTFTs) were successfully fabricated with top contact structure at low fabrication temperature. The thin gate dielectric of OTFTs were deposited by atmospheric pressure plasma jet at substrate temperature about 150° and under atmospheric pressure. The environment of processes would significantly improve the abilities of large area application for display and decrease the cost of instruments. We found that the quality of silicon oxide deposited with atmospheric pressure plasma jet strongly depended on the main gas and the gap distance between the plasma nozzle and the surface of the device and even influenced the deposition rate. Due to the improve of gate insulator quality, excellent electrical characteristics of OTFTs were obtained, including carrier mobility as large as 0.66 cm2/ V . s, operation voltage as low as -2 V, and subthreshold swing as low as 0.7 V/dec.
Preparation of SiOx and SiOxNy Films on PEN using Facing Target Sputtering System
Authors: Kim Hwamin , Sohn Sunyoung
Published: May 2009

In this study, facing target sputtering(FTS) apparatus was fabricated and its process characteristics were investigated to estimate possibility to thin film passivation for optoelectronics. We report that the FTS system can prepare a high quality silicon oxide(SiOx) and silicon oxynitride(SiOxNy) films with a dense micro structure and an excellent uniformity less than 5%. In addition, the low temperature deposition is possible because the bombardment of high energy particles can be restrained. Thus, we suggest that the FTS is one of the suitable deposition techniques for the thin film passivtion layer and the gas barrier layer for optoelectronics.
Improvement of CVD SiO2 by Post Deposition Microwave Plasma Treatment
Authors: Nagata Kohki , Akamatsu Hiroaki , Kosemura Daisuke , Yoshida Tetsuya , Takei Munehisa , Hattori Maki , Ogura Atsushi , Koganezawa Tomoyuki , Machida Masatake , Son Jin-young , Hirosawa Ichiro , Shiozawa Toshihiko , Katayama Daisuke , Sato Yoshihiro , Hirota Yoshihiro
Published: May 2009

We evaluated density and chemical bonding states of the CVD SiO2 film with and without plasma treatment to clarify an effect of the plasma treatment. It was found that the chemical bonding states were homogenized by the plasma treatment from the results of X-ray photoelectron spectroscopy. In addition, an increase of the film density was also observed. These results indicate the densification of SiO2 film, suppression of bond-angle fluctuation, and decrease of impurities (e.g. Hydrogen, Nitrogen and so on) in the SiO2 film. These results can well explain the improvement of the electrical properties by the plasma treatment. Furthermore, UV-Raman measurement was performed to evaluate the modification of Si stress and crystal quality at the SiO2/Si interface.
Effect of KIO3 on Electrochemical Mechanical Removal of Ta/TaN Films
Authors: Govindarajan Rajkumar , Venkataraman Nandhini , Raghavan Srini
Published: May 2009

This paper reports results obtained from the polishing of Ta and TaN films at low pressures (~0.5psi) in solutions containing 2,5 dihydroxy benzene sulfonic acid (DBSA) as a tantalum complexant, potassium iodate (KIO3) as an oxidant and a small amount of silica particles (~0.1wt%), under galvanostatic conditions. Variables such as pH, KIO3 concentration and current density have been investigated to develop an optimized formulation. Solution containing 0.1M DBSA, 0.05M KIO3 and 0.1% silica particles removes tantalum and tantalum nitride at the rates of ~170Aå/min and ~200Aå/min, respectively at 1mA/cm2 current density. Under the same conditions, Ta/Cu selectivity of ~0.8:1 and TaN/Cu selectivity of ~0.9:1 were achieved.
Characterization of Dressing Behaviors and Optimization Technique in Chemical Mechanical Polishing
Authors: Chen Kuen-Ren , Young Hong-Tsu
Published: May 2009

Chemical mechanical polishing (CMP) is the planarization technology most often used for semiconductor processes. The polishing pad needs to be dressed by a dresser to maintain the stability and the throughput of the planarization process. The uniformity of the dressing process is crucial to the in-situ CMP equipment. In this study, the dressing process is characterized by calculating the scratch number of the diamonds over a given cross section of pad and this method was experimentally verified. Effects of different dressing conditions were studied through this model. Then, a uniformity index (UI) was defined to find the optimum sweep frequency for a certain dressing condition. The sweep frequency is the factor that influences the uniformity most. The sweep frequency with small UI can ensure that the pad to be regenerated uniformly anytime. The UI can be obtained under any given dressing conditions.
Optimization of Post-CMP Ultrasonic Cleaning Parameters By Taguchi DOE
Authors: Nagarajan Ramamurthy , Rahul V.
Published: May 2009

Post-CMP cleaning effectiveness is best assessed by studying the cleanliness of polished wafers obtained directly from the CMP process. In this study, a Taguchi DOE was designed as an L27 orthogonal array, and 3 levels of ten CMP and ultrasonic parameters were incorporated in the experimental matrix. The CMP parameters studied were: CMP velocity, pressure, slurry concentration, pH and temperature. The sonication parameters investigated were: frequency, amplitude, pH of the cleaning solution, surfactant type and concentration. The output properties measured were erodability and cleanability. High Level Analysis (HLA) of the DOE data indicate that under conditions of CMP that can embed particles with greater force, lower-frequency (more cavitational) conditions are more effective in particle removal. In general, ultrasonic frequencies in excess of 132 kHz are ineffective in removing strongly-adhered or embedded particles. Ionic surfactants are, in general, more conducive to CMP residue removal compared to non-ionic surfactants (natural, or man-made).
Lab-On-Chip Fabrication of Atomic Scale Magnetic Junctions
Authors: Kemp Neil T. , Majjad Hicham , Lunca-Popa Petru , Dalmas Guillaume , Doudin Bernard
Published: May 2009

We have demonstrated a unique and versatile approach for fabrication and measurement of magnetic nanocontacts on a single chip. Integration of microfluidics is shown to be a key advantage, enabling device miniaturisation as well as rapid and convenient changing of plating solutions. Initial tests are presented, showing that contacts made with thick deposits exhibit properties departing from anisotropic magnetoresistance, and mimicking early results of very large magnetoresistance values.
Crystallographic Damage to Mn-Ir Antiferromagnets by Ion Beam Etching
Authors: Watanabe Katsuro , Ueda Kazuhiro
Published: May 2009

The etching damage caused by ion beam etching with a low energy from 100 to 425 eV to manganese (Mn) - iridium (Ir) antiferromagnets was investigated by fluorescent x-ray analysis and a way of precise grazing incidence-controlled x-ray diffraction. Two kinds of damage were observed: one was an increase in iridium content, which increased as the etching depth (detched) increased. The other kind of damage was a lattice strain. IBE at a higher acceleration voltage (Vacc) and larger detched caused expansion of the in-plane MnIr(220) spacing near the etched surface; the out-of-plane MnIr(202) spacing remained constant. A smaller detched limited the lattice strain. The depth at which the lattice strain occurred was about 12 nm from the surfaces etched with various Vacc's and to various detched's. The causes of these two types of damage might be the same, i.e., preferential etching of Mn atoms at the surface.
Influence of pH on Electrodeposition and Properties of 2.4T CoFe Alloy
Authors: Gong Jie , Riemer Steve , Vas'ko Vlad , Kief Mark , Tabakovic Ibro
Published: May 2009

Electrodeposition of 0.5 mm thick 2.4T CoFe films with 60-63 wt% Fe was achieved at various solution pHs (2.0, 2.2, 2.3, 2.4, 2.6, and 2.8, respectively) in the presence of saccharin on 6 in AlTiC wafers with Cu-seed layer. The effect of pH on electrodeposition including voltammetric behavior, plating rate, and selectivity ratio was discussed. The increase of solution pH affects some material properties like: surface roughness, grain size, morphology, and corrosion. Notably, texture, coercivity, and tensile stress of 0.5 mm 2.4T CoFe films with 60-63 wt. % Fe are less affected by solution pH. Possible reasons for such behavior were discussed.
Long Term Investigations on NiFe Electroplating Processes
Authors: Chen Jue , Hansen Stefan , Gatzen H. H.
Published: May 2009

NiFe alloys are suitable to fabricate the cores of micro actuators and micro sensors. The soft magnetic properties of NiFe45/55 are sufficient for most actuator applications. Electroplating of NiFe45/55 structures enables to fabricate Micro Electro-mechanical Systems (MEMS) using patterned films with a thickness of up to some ten micrometers. One drawback is the fact that the electrolyte used for the electroplating process shows aging effects. This is caused by the generation of Fe3+ ions in the electrolyte. The Fe3+ ion content of the electrolyte influences the saturation flux density and the permeability of the deposited NiFe45/55 structures. A reduction of the Fe3+ ion formation is achieved by a flow of inert gas through the electrolyte. Three plating cells were analyzed using different flow-through concepts for the inert gas. These cells were compared with a reference cell. The electrolyte quality is monitored by measurement of the magnetic properties of deposited films.
Electrodeposition of NiP Film used as a Nonmagnetic Spacer in Laminated (CoFe/NiP)n Writer Pole
Authors: Sun Ming , Riemer Steve , Kief Mark , Tabakovic Ibro
Published: May 2009

Electrodeposition of NiP film used as a thin nonmagnetic spacer in laminated multilayer (2.4T CoFe/NiP)n perpendicular writer pole is described. The electrodeposition of laminated multilayers was carried out in a dual-bath automated electroplating tool. The thin NiP films with thicknesses from 2.0 to 20 nm were obtained as nonmagnetic amorphous alloys with P-content higher than 18 at%. The problem of a concentration gradient at the CoFe/NiP interface, i.e. a lower P-content in the NiP deposit within a distance of 10 nm from the CoFe-interface, was solved by using STI-1 Proprietary organic additive in the plating solution. The details of the electrodeposition of NiP films and their properties are described.
Controlled Synthesis and Magnetic Properties of Iron Oxide Nanostructures using Biogenic Polyamines
Authors: Shanmugam Sangaraju , Nakanishi Takuya , Osaka Tetsuya
Published: May 2009

A facile and simple approach has been described for the synthesis of magnetite nanoparticles and iron oxyhydroxide nanorods using biogenic polyamines. At room temperature, highly crystalline magnetite particles with average size of 44 {plus minus} 2 and 37 {plus minus} 1 nm were synthesized with spermine and spermidine, respectively. The formation of nanoparticles was characterized with TEM, HRTEM, XPS and SQUID. The magnetite nanoparticles formed by the biogenic polyamines exhibits ferromagnetic behavior at 300 K. When the reaction was carried out at low temperature, high aspect ratio, well crystalline nanorods were observed. X-ray diffraction and Infrared spectroscopy suggests that the nanorods correspond to lepidocrocite (γ-FeOOH). TEM analysis shows each bundle consisting of several nanorods stacked together by side on fashion. γ-FeOOH nanorods with high aspect ratio of 70 were observed. The SQUID analysis reveals that the lepidocrocite nanorods exhibit superparamagnetic behavior at room temperature.
Surface Modification of Chemically Synthesized FePt Nanoparticles
Authors: Hachisu Takuma , Yotsumoto Takahiro , Sugiyama Atsushi , Osaka Tetsuya
Published: May 2009

L10-FePt nanoparticle having high magnetic anisotropy is a promising candidate for the future ultra high magnetic recording material. We have succeeded in the fabrication of cubical FePt nanoparticles. It is necessary for high areal recording density to develop a homogeneous assembled technique of the cubical nanoparticle with its magnetic easy axis in the vertical direction on a substrate. It has been known the selective chemical reaction between metal species and functional group of organic molecules. We focused on the selective chemical reaction to control the direction of the magnetic easy axis in the cubical nanoparticle. In this study, the modification of the organic molecule with various functional groups to the surface of the cubical nanoparticle was examined. Consequently, the amino groups were replaced by thiol groups and carboxyl groups on the surface ligands of the nanoparticle were residual, and then, we confirmed bonding thiol group end to Pt atom selectively.
A Concept for the Characterization and Analysis of the Permeability of Soft Magnetic Thin-Films
Authors: Traisigkhachol Ornwasa , Rissing Lutz , Gatzen H. H.
Published: May 2009

A simple approach for accomplishing soft thin film magnetic measurements is evaluated. A modular system based on a pair of HELMHOLTZ coils taken from an existing magnetometer was designed. To characterize it, a quantitative comparison between analytic calculations, Finite Element Methode (FEM) simulation and measurements was conducted. The field uniformity over the measured area of 10 cm along the x-axis was found to be within1.6% of toleration; a sampling rate of 50 kSPS and 50 Hz external magnetic field excitation frequency were used. The system setup and analysis methods were analyzed. The system shows high correlations to other magnetometers, that allows easy calibration with commercial HALL sensors and other magnetometers. The measurement of electroplated NiFe samples fabricated in thin-film technology at the imt demonstrated the validity of the approach.