bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Oxygen-doping on Crystallization and Physical Properties of Ge2Sb2Te5 Films
Authors: Perng Yu-Hsung , Hsu Ying-Tai , Chou Lih-Hsin 
Published: April 2011

ABSTRACTOxygen-doped Ge2Sb2Te5 films (denoted as Ge2Sb2Te5-O) with oxygen concentration in between 0 and 10.3 at. % were prepared by direct current magnetron reactive sputtering with Ge2Sb2Te5 target. Both the crystallization temperature and activation energy of Ge2Sb2Te5-O films increased, while the crystalline grain size refined with oxygen concentration. For both amorphous and crystalline phases, optical band gap Egopt increases with oxygen concentration – a similar trend as observed in resistivity measurements. X-ray diffraction results showed that the face center cubic (fcc) structure maintained even after 400°C anneal with oxygen addition in between 7.5 − 8.3 at.% - a different phenomenon from undoped Ge2Sb2Te5 film, but with crystallinity diminished gradually with oxygen concentration. Only Sb2Te3 diffraction peak was observed in the 10.3 at.% O film after 400°C anneal. In conjunction with the bonding information obtained from X-ray photoelectron spectroscopy (XPS), effects of oxygen on the microstructures, thermal properties, resistivity and stability of fcc structure are examined and the embedded mechanisms are discussed in this study.
Investigations of High Endurance Asymmetric Phase Change Random Access Memory
Authors: Lee Hock Koon , Shi Luping , Zhao Rong , Yang Hongxin , Lim Kian Guan , LI Jianming , Chong Tow Chong 
Published: April 2011

ABSTRACTAsymmetric PCRAM structure with the upper contact opening at an offset to the bottom contact opening allowed us to improve the thermal distribution within the phase change layer and lower the reset current to 50% that of a conventional symmetrical structure. In terms of endurance, asymmetric cell lasted for 1.1 × 108 cycles which is at least 10X higher than the conventional symmetrical cell. These results were based on Ge2Sb2Te5 as the phase change material.In this paper, we used nitrogen doped Ge2Sb2Te5 [1] instead and the thickness of this phase change layer was 100 nm. During the sputtering of Ge2Sb2Te5, the Argon gas flow rate was fixed at 15 sccm while nitrogen flow rates of 0, 3, 4.5 and 6 sccm were introduced each time. Thus N2/Ar gas ratio of 0, 0.2, 0.3 and 0.4 were obtained respectively. After fabrication, the cell endurance of Asymmetric PCRAM cells incorporating Ge2Sb2Te5 doped with varying concentrations of nitrogen was tested. During testing, the PCRAM was repeatedly Reset/Set and the resistances of the two states were recorded at every 100k cycles. The cell was considered to be functioning well when its Reset/Set resistance ratio was greater than 10. From experiments, N-doped asymmetric cell with N2/Ar gas ratio of 0.2 lasted 2.4 × 1010 cycles which is 1000 times that of a conventional symmetrical PCRAM cells. The N2 doping concentration was also shown to be optimized when the N2/Ar gas ratio was fixed at 0.2. Higher doping concentrations with N2/Ar gas ratio of 0.3 and 0.4 decreased the cell endurance to 8.8 × 108 and 7.6 × 108 cycles respectively. Excessive doped nitrogen atoms might have degraded the phase change material, causing breakdown to occur sooner.N-doped conventional symmetrical PCRAM was also fabricated and its overwrite cycles were measured only up to 1.2 × 109. With better thermal confinement, asymmetric PCRAM has proved to be better in endurance too. The above results were based on asymmetric PCRAM cells with 1 µm offset.[1] H. Horii et al, “A Novel Cell Technology Using N-doped GeSbTe Films For Phase Change RAM”, p. 177-178, VLSI Tech. 2003
Oxygen Vacancies in Amorphous HfO2 and SiO2
Authors: Kaneta Chioko , Yamasaki Takahiro 
Published: April 2011

ABSTRACTFormation energies and electronic properties of oxygen vacancies in amorphous HfO2 gate dielectrics are investigated by employing the first-principles method based on the density functional theory. We have found that the formation energy of neutral oxygen vacancy in amorphous HfO2 distributes from 4.7 to 6.1 eV, most of which is lower than the value for cubic HfO2, 6.0 eV. We also investigated the stabilities of the Vo pairs in various charged state and compared with those in amorphous SiO2. We found that Vo++ is stabilized in the vicinity of Vo in SiO2. In HfO2, however, this does not happen. This suggests the difference of defect propagation mechanism in HfO2 and SiO2.
Work Function Tuning of MoxSiyNz metal gate electrode for Advanced CMOS Technology
Authors: Patel Pommy , Buchanan Douglas A , Wallace Robert M 
Published: April 2011

ABSTRACTDue to continued transistor scaling, the work function tuning of metal gates has become important for advanced CMOS applications. The primary objective of this research is to understand the tuning of the MoxSiyNz (also referred to as MoSiN) gate work function through the incorporation of nitrogen. A molybdenum silicide (MoSi2) target was reactively sputtered in nitrogen (N2) and argon (Ar) plasma. The amount of nitrogen in the MoSiN films was varied by controlling the gas flow ratio, RN = N2/(N2+Ar). Capacitance-voltage (CV) and internal photoemission (IPE) measurements are used to extract the work function (ϕm) of the MoSiN gate. A decrease in the MoSiN work function was observed from ∼4.7eV to ∼4.4eV for an increase in the gas flow ratios from 10% to 40%. The SIMS depth profiles suggested a uniform distribution of nitrogen throughout the films. The XPS surface analysis confirmed a steady increase in the total nitrogen concentration in the MoSiN films as gas flow ratio was increased. The increase in N2 concentration corresponded directly with the lowering of the MoSiN work function. These results clearly demonstrated that the MoSiN work function maybe altered over ∼0.3 eV tuning window by adjusting the N2 concentration in these films.
Combinatorial Pulsed Laser Deposition of ITO-ZnO:Al Thin Films for Solar Cells Applications
Authors: Craciun Doina , Socol Gabriel , Mihailescu Ion N. , Craciun Valentin 
Published: April 2011

ABSTRACTTransparent and conductive mixtures of ITO-ZnO and ITO-ZnO:Al have been deposited by a combinatorial pulsed laser deposition on Si and quartz substrates. Measurements of the In to Zn ratios along the transversal axis of the substrates were performed using energy dispersive x-ray spectroscopy. From simulations of the x-ray reflectivity spectra, collected with a 2 mm mask on different locations along the transversal axis of the samples, the density and thickness of the deposited films were calculated and then the In to Zn ratios. The crystalline structure and electrical properties of the deposited films were also investigated along the same axis. Changes in the ratio of In/Zn along this axis resulted in changes of the lattice constant, texture, optical and electrical properties of the films. By changing the In to Zn ration we could tailor the properties of the transparent electrode and found ways to partially replace the more expensive ITO material with ZnO.
Carrier Compensation Mechanism of Highly Conductive Anatase Ti0.94Nb0.06O2 Epitaxial Thin Films
Authors: Nogawa Hiroyuki , Hitosugi Taro , Kamisaka Hideyuki , Yamashita Kouichi , Chikamatsu Akira , Yoshimatsu Kouhei , Kumigashira Hiroshi , Oshima Masaharu , Nadao Syoichiro , Furubayashi Yutaka , Hirose Yasushi , Shimada Toshihiro , Hasegawa Tetsuya 
Published: April 2011

ABSTRACTWe investigated electrical conduction of anatase Ti0.94Nb0.06O2 (TNO) epitaxial thin films in relation to oxygen defects generated by post-annealing. Annealing of TNO in oxygen was found to cause dramatic decreases in ne. Resonant photoemission spectroscopy measurements revealed that a deep acceptor state just above the top of valence band evolves, synchronized with the decrease of ne. We proposed that the acceptor state originates from interstitial oxygen atoms combined with Nb dopants and compensates electron carriers.
Integrated (Ba,Sr)TiO3 Thin-Film Technology for RF and Microwave Applications
Authors: Suzuki Toshimasa , Ishii Daiki , Iwazaki Yoshiki , Morito Kentaro , Mizuno Youichi 
Published: April 2011

ABSTRACTThe microwave tunable capability and its related material optimization of (Ba,Sr)TiO3 thin films in the parallel-plate capacitor form is discussed in terms of the dependence of barium concentration, acceptor doping, and in-plane film stress, based on the present broadband microwave characterization technique under various bias fields. The barium-content dependence indicates the tradeoff between tunability and dielectric loss, and the notable field-induced loss in SrTiO3 is confirmed as an intrinsic quasi-Debye contribution. The Mg dopant incorporated into a perovskite lattice shows almost no effectiveness on tunable device performance, except for enhanced insulation as an electron acceptor, while the low bias-field dependence of the dielectric loss suggests the possibility of the partial occupation of the alkaline-earth-ion site by Mg. The reduction of in-plane thermal stress controlled by the pressure during sputtering deposition leads to higher permittivity and tunability while degrading the film crystallinity by ion bombardment. The low-frequency loss tends to increase with crystal damage; however, the microwave loss remains unchanged, revealing the applicability of sputtering stress control to real microwave devices. In addition, we demonstrate the operation of an analog phase shifter using parallel-plate ferroelectric tunable capacitors and its application to a phased array antenna monolithically integrated on a silicon substrate.
Characterisation of PZT in Thin Film Bulk Acoustic Wave Resonators
Authors: Conde Janine , Muralt Paul 
Published: April 2011

ABSTRACTPb(Zr0.53, Ti0.47)O3 (PZT) thin films are potentially interesting as piezoelectric layer in bulk acoustic wave (BAW) resonators. We investigated properties and performance of {111} and {100} textured, dense films deposited by sol-gel techniques in the frequency range of 1 to 2 GHz. The resonators were fabricated on Si wafers using deep silicon etching to create a membrane structure and using platinum as top and bottom electrodes. The best response of the resonators was observed at a bias voltage of −15kV/cm with values of around 10% for the coupling constant and around 50 for the quality factor. This voltage corresponds to the maximal value of the piezoelectric constant d33 and minimal value of the dielectric permittivity measured as a function of the electric field. Resonance and antiresonance frequencies were strongly influenced by a bias voltage, showing a hysteretic behaviour as expected for ferroelectrics. Both of these frequencies shifted in the same direction. As a consequence, the dc voltage can be potentially used to shift the whole band of a filter. In unipolar operation, the coupling constant could be varied from 6 to 10 %. Materials parameters were extracted from the admittance as a function of frequency. Dielectric, piezoelectric and elastic properties of textured PZT films are reported and compared to direct (low frequency) measurements and to literature values. It was found that PZT thin films have lower stiffness than the one of PZT bulk ceramics and it was observed that {111}-textured films are stiffer than {100}-textured films.
Mechanical Integrity of Hybrid Components used in Flexible Optoelectronic Devices
Authors: Sierros Konstantinos A , Morris Nicholas J , Abell J Stuart , Cairns Darran R , Kukureka Stephen N. 
Published: April 2011

ABSTRACTFabrication of truly flexible optoelectronic devices, such as flexible displays and flexible photovoltaics, is highly dependent on the mechanical integrity of individual thin inorganic/organic hybrid device components. A common feature of almost all thin composite film components for flexible optoelectronic applications is indium tin oxide (ITO) coated on polyester.The mechanical mismatch of the ITO ceramic coating, a few tens of nm thick, with the polyester, either polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), 125 ìm thick, causes the flexible functional structure to fail at moderately low strains under various, externally applied, stress states. It is therefore important to assess the mechanical integrity of such hybrid systems experimentally. We report on the electromechanical behavior of such hybrid systems.
High-Speed, High-Sensitivity Polyimide Humidity Sensors Based on MEMS Microhotplates
Authors: Kim Jea Sung , Kim Tea Jin , Kang Moon Sik , Yoo Kum Pyo , Min Nam Ki 
Published: April 2011

ABSTRACTPolyimides thin films, which are the most commonly used group of sensing materials for capacitive humidity sensors, were cured locally using MEMS microhotplates. The polyimide locally cured at temperature over 350 °C for 1 hour was fully cured. There were no significant differences in the polyimide thin films between cured in convection ovens and locally cured on microhotplate. The locally cured polyimide humidity sensor showed a linearity of 0.9995, a sensitivity of 0.766pF/%RH, a hysteresis of 0.6%RH, and a time response of 3 s. These results show the possibility of locally-cured polyimide films as high speed, high-sensitivity humidity sensors.
UV Laser Ablation of PLZT and PSZT Films
Authors: Leech Patrick W , Holland Anthony S , Sriram Sharath , Bhaskaran Madhu 
Published: April 2011

ABSTRACTThe ablation of strontium-doped lead zirconate titanate (PSZT) and lanthanum-doped lead zirconate titanate (PLZT) films has been examined using a 5 ns pulsed excimer laser. Individual squares were patterned with sides in the range of 10-30 µm using single and multiple pulses. The depth of ablation in PLZT films was higher at all fluences than in PSZT films. The morphology of the etched surfaces has comprised the formation of globules which had diameters of 200-250 nm in PLZT and 1400-1600 nm in PSZT films. The diameter of the globules has been shown to increase with fluence until reaching an approximately constant size at >20 J/cm2 in both types of film. The composition of the films following ablation has been analyzed using x-ray photoelectron spectroscopy (XPS) and energy dispersive x-ray (EDX) spectroscopy.
Quantum Well and Quantum Dot Based Detector Arrays for Infrared Imaging
Authors: Gunapala Sarath , Bandara Sumith , Hill Cory , Ting David , Liu John , Mumolo Jason , Keo Sam , Blazejewski Edward 
Published: April 2011

ABSTRACTA mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) 320x256 pixel quantum well infrared photodetector (QWIP) dualband focal plane arrays (FPAs) have been demonstrated with excellent imagery. Currently, we are developing a 1024x1024 pixel simultaneous pixel co-registered dualband QWIP FPA. In addition, epitaxially grown self-assembled InAs/InGaAs/GaAs quantum dots (QDs) are exploited for the development of large-format FPAs. The Dot-in-a-Well (DWELL) structures were experimentally shown to absorb both 45° and normal incident light, therefore a reflection grating structure was used to enhance the quantum efficiency. The devices exhibit peak responsivity out to 8.1 microns, with peak detectivity reaching ∼ 1 × 1010 Jones at 77 K. The devices were fabricated into the first LWIR 640x512 pixel QDIP FPA, which has produced excellent infrared imagery with NETD of 40 mK at 60K operating temperature.
Development Effort of the Lunar Orbiter Laser Altimeter Laser Transmitter
Authors: Shaw George B , Yu Anthony W , Novo-Gradac Anne-Marie D 
Published: April 2011

ABSTRACTThe Lunar Orbiter Laser Altimeter (LOLA) is one of six instruments on the Lunar Reconnaissance Orbiter (LRO) with the objectives to determine the global topography of the lunar surface at high resolution, measure landing site slopes and search for polar ices in shadowed regions. The LOLA laser transmitter is a passively q-switched cross-Porro resonator. The flight laser beryllium bench houses two oscillators (a primary oscillator and a cold spare). The two oscillators are designed to operate sequentially during the mission. The secondary laser will be turned on if the primary laser can no longer provide adequate scientific data products. All components used in the laser have space flight heritage. In this paper we will summarize the development effort of the LOLA laser including the material choice, design criteria and contamination control as applied to the flight laser build.
Dielectric Recovery of Plasma Damaged Organosilicate Low-k Films
Authors: Huang Huai , Bao Junjing , Huang Huai , Liu Junjun , Smith Ryan Scott , Sun Yangming , Ho Paul S. , McSwiney Michael L. , Moinpour Mansour , Kloster Grant M 
Published: April 2011

ABSTRACTMethyl depletion and subsequent moisture uptake have been found to be the primary plasma damages leading to dielectric loss in porous organosilicate (OSG) low-k dielectrics. A vacuum vapor silylation process was developed for dielectric recovery of plasma damaged OSG low-k dielectrics. The methyl or phenyl containing silylation agents were used to convert the hydrophilic -OH groups to hydrophobic groups. Compared with Trimethylchlorosilane (TMCS) and Phenyltrimethoxysilane (PTMOS), Dimethyldichlorosilane (DMDCS) was found to be more effective in recovering surface carbon concentration and surface hydrophobicity. But the carbon recovery effect was limited to the surface region.Alternatively, UV radiation with thermal activation was applied for dielectric recovery of plasma damaged OSG low-k dielectrics. The combined UV/thermal process was found to be efficient in reducing −OH, physisorbed water, and C=O bonds. The dielectric constant was recovered within 5% of the pristine sample and the leakage current was also much reduced. Aging test in air showed that no moisture retake was observed, indicating the repaired film was stable.
Patterned wafers backside thinning for 3-D Integration and multilayer stack achievement by direct wafer bonding
Authors: Charlet Barbara , Chiteboun Antoine , Zussy Marc , Bally Laurent , Leduc Patrick , Assous Myriam 
Published: April 2011

ABSTRACTScaling down the devices to keep increasing the integrated circuits (ICs) performance at the rate defined by Moore's [1] law becomes more and more difficult and so costly that new circuits architectures and new integration technologies are investigated. One of the most promising ways in integration technology is the vertical stacking of circuits, also called “3D Integration”. One of the challenges in this technology is the patterned substrate backside thinning. Compatibility with the whole 3D Integration process has to be guaranteed, the existing circuit has to be kept intact and the bonding interface mustn't be damaged. In this study we discuss some experimental results of wafer thinning by grinding and polishing of molecular bonded silicon wafers applied to 3D Integration [2-4]. The wafer with patterned copper interconnections are stacked by direct SiO2 bonding and thinned down on one backside. These stacks are then bonded again to one or two circuits via a deposited oxide on the thinned surface. The top bulk Si surface was thinned down again on one backside, giving a multi layers stack. This wafer level vertical assembly demonstrates the possibility to adjust the remaining Silicon thickness to small values (<15μm) and then bond the thinned surface to achieve multiple layer 3D structure.
Changes of UV Optical Properties of Plasma Damaged Low-k Dielectrics for Sidewall Damage Scatterometry
Authors: Marsik Premysl , Urbanowicz Adam , Vinokur Klara , Cohen Yoel , Baklanov Mikhail R 
Published: April 2011

ABSTRACTPorous low-k dielectrics were studied to determine the changes of optical properties after various plasma treatments for development of scatterometry technique for evaluation of the trench/via sidewall plasma damage. The SiCOH porogen based low-k films were prepared by PE-CVD. The deposited and UV-cured low-k films have been damaged by striping O2Cl2, O2, NH3 and H2N2 based plasmas and CF4/CH2F2/Ar etching plasma. Blanket wafers were studied in this work for the simplicity of thin film optical model. The optical properties of the damaged low-k dielectrics are evaluated the using various angle spectroscopic ellipsometry in range from 2 to 9 eV. Multilayer optical model is applied to fit the measured quantities and the validity is supported by other techniques. The atomic concentration profiles of Si, C, O and H were stated by TOF-SIMS and changes in overall chemical composition were derived from FTIR. Toluene and water based ellipsometric porosimetry is involved to examine the porosity, pore interconnectivity and internal hydrophilicity.
Pd Segregation at (001) B2-NiSi/Si Epitaxial Interface Studied by Density Functional Theory
Authors: Kim Dae-Hee , Seo Hwa-Il , Kim Yeong-Cheol 
Published: April 2011

ABSTRACTPd segregation at (001) B2-NiSi/Si epitaxial interface was studied by using density functional theory (DFT). An epitaxial interface between 2×2×4 (001) B2-NiSi supercell and 1×1×2 (001) Si supercell was first constructed by adjusting the lattice parameters of B2-NiSi structure to be matched with those of Si structure. We chose Ni atoms as terminating layer of the B2-NiSi, and an equilibrium gap between the B2-NiSi and Si was calculated to be 1.1 Å. The Ni atoms in the structure moved away from the original positions along z-direction in a systematic way during the energy minimization. Two different Ni sites were identified at the interface and the bulk, respectively. The Ni sites at the interface farther away from the interface were more favorable for Pd substitution.
Dependence of thermal stability of NiSi and Ni(Pt)Si /Si on crystal orientation
Authors: Okubo Kazuya , Kawamura Kazuo , Akiyama Shinich , Kotaka Yasutoshi , Itani Tsukasa , Watatani Hirofumi , Yanai Kenichi , Nakaishi Masafumi , Kase Masataka 
Published: April 2011

ABSTRACTWe report NiSi and Ni(Pt)Si films with excellent thermal stability showing a particular crystal orientation on Si(001). The Ni-silicide film with a deposition temperature of about 200 °C consists of a conformal domain structure. We examined detail crystallographic analysis of silicide and clarified the psudo-epitaxial growth of NiSi(202)//Si(220) [or NiSi(211)//Si(220)] was the key scheme of superior thermal stability. By using this optimized Ni-silicide formation process, we have fabricated Ni-silicide that is thermally stable up to 650 °C and shows low fluctuation in sheet resistance and low leakage current in electrical measurements. This process is a promising candidate for future silicidation technology.
Electromigration of Cu Interconnect Lines Prepared by a Plasma-based Etch Process
Authors: Liu Guojun , Kuo Yue 
Published: April 2011

ABSTRACTThe electromigration performance of Cu lines patterned by a Cl2 plasma-based etch process has been studied with the accelerated isothermal lifetime test. An electromigration activation energy of 0.6 eV and a current density acceleration exponent of 2.7 were obtained. Both the copper-silicon nitride cap layer interface and the copper grain boundary were active diffusion paths. The applied mechanical bending stress changed the electromigration void distribution in the film, which leaded to the shorter lifetime and lower activation energy.
Fabrication and Electronic Characteristics of Silicon Nanowire MOSFETs
Authors: Yoshioka Hironori , Nanen Yuichiro , Suda Jun , Kimoto Tsunenobu 
Published: April 2011

ABSTRACTThe n-type silicon nanowire MOSFETs with a nanowire shape being triangular or trapezoidal, have been fabricated on SOI substrates and characterized. The height and bottom-width of the triangular nanowire has been 10 nm and 19 nm, respectively. The devices have shown good gate control, such as a nearly ideal subthreshold slope of 63 mV/decade, high Ion/Ioff ratio of 107, and small drain-induced barrier lowering of 5 mV/V at room temperature. The low field mobility of triangular nanowire has been estimated to be 130 cm2/V·s and shown no difference with the change of the nanowire shape and direction within the investigated range.