bluuebunny/crossref_metadata_2025 huggingface dataset:
Highly Conductive p-Type Silicon Carbon Alloys Deposited by Hot-Wire Chemical Vapor Deposition
Authors: Chen Tao , Yang Deren , Carius Reinhard , Finger Friedhelm
Published: April 2010

P-type microcrystalline silicon carbide (µc-SiC:H) alloys for application as a window layer in silicon based thin film solar cells were grown by hot-wire chemical vapor deposition using hydrogen diluted monomethylsilane and trimethylaluminum. Conductivities up to 0.1 S/cm were obtained for p-type material. The optical properties were studied by photothermal deflection spectroscopy. At photon energies below 1.25 eV, both free carrier and defect absorption lead to a high absorption coefficient. For photon energies >2.0 eV, the absorption coefficient is affected by the crystallinity and the structural composition. The structure of Al-doped µc-SiC:H thin films were investigated by infrared and Raman spectroscopy. It was found that increase of the deposition pressure can compensate for the loss of crystallinity caused by Al-doping. At high deposition pressure (>100 Pa), increasing contributions of hexagonal SiC alloys, and separated carbon phases are observed.
Ambipolar Transport in Bilayer Organic Field-Effect Transistor Based on Poly(3-hexylthiophene) and Fullerene Derivatives
Authors: Morita Takeomi , Singh Vipul , Oku Shinya , Nagamatsu Shuichi , Takashima Wataru , Hayase Shuzi , Kaneto Keiichi
Published: April 2010

Ambipolar characteristics in an organic field-effect transistor (FET) with a bilayer structure consisting of poly(3-hexylthiophene) (P3HT) and a fullerene derivative (PCBM) are reported. P3HT was deposited by a floating film transfer method (FTM) with toluene solution on spin-coated PCBM. The FTM-deposited film was found to show relatively high hole mobility even when cast using toluene solution. Even after coating P3HT on PCBM by FTM, a relatively high n-type transport was obtained. This indicates that FTM employed in this study is a mild way to coat an organic thin film on an organic semiconductor layer in terms of minimizing the effect of carrier transport in the underlayer. The transport characteristics have been discussed in comparison with those of ambipolar FETs prepared by other methods previously reported.
Can Acid Amplifiers Help Beat the Resolution, Line Edge Roughness, and Sensitivity Trade-Off?
Authors: Kruger Seth , Higgins Craig , Revuru Srividya , Gibbons Sarah , Freedman Dan , Brainard Robert L.
Published: April 2010

In this paper, we describe the structures of several new acid amplifiers and of extreme ultraviolet (EUV) resist formulations prepared from them. We have synthesized and lithographically evaluated eleven new compounds specifically designed for use as acid amplifiers in EUV resists. We make direct comparisions between resolution, line-edge roughness (LER) and sensitivity using the common resolution, line-edge roughness, and sensitivity (RLS) analysis technique of Z-parameter. We show that acid amplifiers are capable of simultaneously improving resolution, LER, and sensitivity.
Investigation of PbI2 Film Fabricated by a New Sedimentation Method as an X-ray Conversion Material
Authors: Yun Min-seok , Cho Sung-ho , Lee Rena , Jang Gi-won , Kim Yun-seok , Shin Woon-jae , Nam Sang-hee
Published: April 2010

Radiation detectors are currently fabricated by a screen-print method at room temperature. However, this method has many disadvantages in terms of thickness control and electron trapping. We fabricated polycrystalline PbI2 films by a new sedimentation method and compared the results with those obtained by the existing screen-print (SP) method. We investigated the electrical and structural properties of the films. We fabricated 2 ×2 cm2 sample films with a thickness of about 200 µm. A field emission scanning electron microscopy (FE-SEM) analysis showed that these films were of higher density than those fabricated by a conventional SP method. We also measured the photosensitivity and dark current of the films. The photosensitivity of the films fabricated by the new sedimentation method was 4.8 pC/(mR·mm2), and the dark current was 2.2 pA/mm2 at 1.0 V/µm. The linearity of the film ranged from 3 to 12 mAs, which is promising for diagnostic radiography.
Collimated Light Source Using Patterned Organic Light-Emitting Diodes and Microlens
Authors: Aratani Sukekazu , Adachi Masaya , Shimizu Masao , Sugita Tatsuya , Shibasaki Toshinari , Shimazaki Katsusuke
Published: April 2010

We developed for the first time a collimated organic light-emitting diode (OLED) light source using a patterned OLED and a microlens. The structure of the collimated OLED light source was designed by conventional ray-tracking simulation. We demonstrated that the collimated OLED light source enhanced the luminance of a liquid crystal display (LCD) with a low aperture ratio by a factor of more than two compared with a conventional OLED light source, which was not patterned. The collimated OLED light source with the patterned OLED and microlens is thus very effective for achieving a highly efficient LCD with OLED backlight.
Electron-Bombardment-Induced Damage to Organic Light Emission Layer
Authors: Lei Hao , Hoshi Yoichi , Wang Meihan , Uchida Takayuki , Kobayashi Shinichi , Sawada Yutaka
Published: April 2010

Damage to an aluminum(III) bis(2-methyl-8-quinolinato)-4-phenylphenolate (BAlq) organic film by direct electron irradiation was investigated. An electron-bombardment system, which can supply a desired amount and energy of electrons, was set up. Changes in the photoluminescence (PL) intensity of the BAlq layer were used to evaluate the damage produced by electron bombardment. A marked reduction of the PL intensity was observed with the increase in the amount and energy of electrons irradiated to the BAlq films, although no changes in the Fourier transform infrared (FTIR) spectra of the BAlq layer due to electron bombardment were detected. A change in surface morphology, however, was observed by atomic force microscopy (AFM). These results suggest that electron bombardment induces significant damage to the organic layer and that a reduction of electron bombardment during the sputter deposition of electrode films is necessary to improve the performance of the organic layer.
Optical and Solar Cell Properties of Alpha-ray, Proton, and Gamma-ray Irradiated Cu(In,Ga)Se2 Thin Films and Solar Cells
Authors: Sugiyama Mutsumi , Yasuniwa Toshihiro , Nakanishi Hisayuki , Chichibu Shigefusa F. , Kimura Shinichi
Published: April 2010

The effects of alpha-ray, proton, and gamma-ray irradiation on the electrical properties of Cu(In,Ga)Se2 (CIGS) solar cells and the photoluminescence spectra of CIGS and CuInSe2 (CIS) thin films were investigated. Particle irradiation using alpha-ray and proton primarily degraded the interfaces of CIGS solar cells, even though the CIS and CIGS thin films did not degraded, in the case of a low irradiation fluence of the order of 109 cm-2. On the other hand, CIS and CIGS showed good tolerance to gamma-ray irradiation because the impact of wave radiation is insufficient to degrade the crystal, in comparison with particle radiation. These results will become the first step toward realizing practical applications of CIGS solar cells in space and clarifying their degradation mechanism.
Excellent Brightness with Shortening Lifetime of Textured Zn2SiO4:Mn2+ Phosphor Films on Quartz Glass
Authors: Park Jehong , Park Kwangwon , Lee Jaebum , Kim Jongsu , Kim Seongsin Margaret , Kung Patrick
Published: April 2010

Green-emissive textured Zn2SiO4:Mn2+ phosphor films were fabricated by the thermal diffusion of ZnO:Mn on quartz glass. The Zn2SiO4:Mn2+ phosphor films became textured along several hexagonal directions and their chemical composition was continuously graded at the interface. The decay time of Mn2+ was as short as 4.4 ms, and the optical transition probability of the films defined as the inverse of decay time showed a strong correlation with film texture degree as a function of annealing temperature. The brightest Zn2SiO4:Mn2+ film showed a photoluminescent brightness as high as 65% compared with a commercial Zn2SiO4:Mn2+ phosphor powder screen and a maximum absolute transparency of 70%. These excellent optical properties are explained by the combination of the unique textured structure and continuous grading of the Zn2SiO4:Mn2+ chemical composition at the interface.
Surface Roughness of Laser-Shock-Peened Aluminum Alloys and Its Effect on the Dispersion of Surface Acoustic Waves
Authors: Shen Zhong-Hua , Duan Ya-Xuan , Ren Xu-Dong , Ni Xiao-Wu
Published: April 2010

The experimental dispersion curves of laser-shock-peened aluminum samples were obtained from the phase spectra of the laser induced surface acoustic waves (SAWs) and the results indicated that the more the peening times, the greater the dispersion. The change in phase velocity resulting from the surface roughness was obtained by comparing the dispersions of the samples before and after being polishing. It was found that the surface roughness decreased the phase velocity, and the change in velocity depended on the frequency of the SAW as expected from the theoretical analysis of the case when the lateral correlation length is much smaller than the wavelength of the SAWs. Furthermore, the experimental dispersion results of the SAWs for three samples with different peening times showed that the more the peening times, the smaller the roughness, which was verified by the values measured with a roughmeter.
Single-Event Correlation Analysis of Quantum Key Distribution with Single-Photon Sources
Authors: Dong Shangli , Wang Xiaobo , Zhang Guofeng , Xiao Liantuan , Jia Suotang
Published: April 2010

Multiple photons exist that allow efficient eavesdropping strategies that threaten the security of quantum key distribution. In this paper, we theoretically discuss the photon correlations between authorized partners in the case of practical single-photon sources including a multiple-photon background. To investigate the feasibility of intercept-resend attacks, the cross correlations and the maximum intercept-resend ratio caused by the background signal are determined using single-event correlation analysis based on single-event detection.
Transmittance Fluctuation from Nearly Extinct Nematic Cells
Authors: Sumiyoshi Ken
Published: April 2010

By introducing geometrical optics approximation (GOA) solutions to a nearly extinct homogeneous nematic director, the effects of assembly misalignment and director fluctuation on light leakage transmittance are studied. Transmittance expressions including fluctuation swing are obtained for three misoriented cases: misaligned homogeneous case, misaligned analyzer case, and mistwisted nematic case. Except for the misaligned homogeneous case with second-order fluctuation, all the other expressions have a linear contribution caused by their own misorientation. From these results, the transmittance variance from fluctuation at a misaligned situation is more enhanced than that in the extinction situation. After introducing thermal average statistics, expressions for the average and variance of transmittance with fluctuation are given. A numerical estimation for these expressions shows that in the misaligned homogeneous case by 1°, the standard deviation of transmittance is 20% of its average.
Electrical Characterization of Metal–Silicon Microwire Interface Using Conductive Atomic Force Microscope
Authors: Moiz Syed Abdul , Jee Sang-Won , Um Han-Don , Lee Jung-Ho
Published: April 2010

Ni-catalyzed silicon microwires (SiMWs) were grown on n-Si(111) substrate. The bottom contacts of the SiMWs were selectively formed using Ni electrodeposition at the substrate. The current–voltage (I–V) characteristics of the microwires were measured using conductive atomic force microscope (CAFM). Different charge transport models such as thermionic-emission, field-emission and thermionic-field-emission were applied to the measuredI–Vcharacteristics of the metal–SiMW–metal structures in the array. It was observed that the thermionic-field-emission and field-emission were the leading Schottky transport mechanisms needed to explain the measuredI–Vresponses in forward and reverse bias respectively. By applying the thermionic-field-emission model to the measuredI–Vcharacteristics of SiMW array, parameters such as conductivity, free carriers density and mobility were estimated and discussed. It was also observed that the average estimated mobility of the carriers in SiMW array was lower than the reported bulk mobility. It may be due to the fact that higher aspect ratio, nonliner doping concentration both at radial as well as axial direction of SiMWs and surface scattering of the carriers were dominant and hence it degraded the mobility of the SiMW array.
Effect of H2Carrier Gas on the Growth of GaN Nanowires on Si(111) Substrates by Metalorganic Chemical Vapor Deposition
Authors: Ra Yong-Ho , Navamathavan Rangaswamy , Cha Jun-Ho , Song Ki-Young , Lim Hong-Chul , Park Ji-Hyeon , Kim Dong-Wook , Lee Cheul-Ro
Published: April 2010

We report on the morphological changes of GaN nanowires (NWs) induced by varying H2carrier gas flow rate. The GaN NWs were grown on Au-coated silicon (111) substrates by metalorganic chemical vapor deposition (MOCVD). The surface morphology and optical characterization of the grown GaN NWs were studied by field-emission scanning electron microscopy (FE-SEM) and photoluminescence (PL) and cathodoluminescence (CL) measurements, respectively. The GaN NWs with uniform diameters from bottom to top sizes ranging from 60 to 100 nm and lengths up to 2–3 µm were obtained. Energy-dispersive X-ray spectroscopy (EDX) analysis confirmed the presence of gallium and nitrogen in the grown GaN NWs. It was observed that the lateral growth behavior of the GaN NWs prevailed in the absence of H2carrier gas. On the other hand, the vertically aligned growth tendency of the GaN NWs was induced by the supply of H2carrier gas.
Experimental and Numerical Studies of Heat Convection in the Synthesis of Single-Walled Carbon Nanotubes by Arc Vaporization
Authors: Tan Guodong , Mieno Tetsu
Published: April 2010

Numerical analysis on heat convection in the synthesis of single-walled carbon nanotubes (SWNTs) by arc vaporization is carried out to calculate the cooling rate of carbon clusters and the temperature distribution of the buffer gas (helium) during the synthesis. The effects of three factors, gravity (G = 1, 2, and 3g
0, where 1g
0 is normal earth gravity), input power (P = 500, 1000, 2000, and 3000 W), and buffer gas pressure ( p = 40, 50, 80, and 100 kPa) are investigated. By comparing the calculated results with those of a previous synthesis experiment under gravity conditions of G = 1, 2, and 3g
0, it is clarified that differences in the cooling rate and the shape of the high-temperature region of the buffer gas cause considerable changes in both the yield and quality of SWNTs produced. The similarity of the heat convection under different input powers and buffer gas pressures is also considered.
Structure, Electrical, and Mechanical Properties of Silver Nanocontacts
Authors: Masuda Hideki , Kizuka Tokushi
Published: April 2010

Silver (Ag) nanocontacts (NCs) were produced by the retraction of a Ag nanotip from its contact with a Ag plate at room temperature inside a transmission electron microscope. The nanotip–plate distance was increased with a constant speed to thin the NCs, and the atomic configuration, applied force and stress, conductance, and current density of the NCs were investigated. The stress during thinning was analyzed as a function of strain, and the Young's modulus of the NCs was estimated. It was found that the Young's modulus, i.e., the elastic property, of the NCs changes when the minimum cross-sectional width of the NCs decreases to less than ∼1 nm. The critical shear stress of the NCs increased to 0.2 GPa when the width decreased to less than ∼1.5 nm, suggesting that the deformation mechanism of the NCs changed from dislocation-mediated slips to homogeneous slips owing to thinning. The nanotip–plate distance was also controlled using a conductance feedback system. Ag NCs exhibiting conductances of 1–3G
0 (where G
0 = 2e
2/h; where e is the charge of an electron and h is Planck's constant) were observed continuously. When feedback conductance was assigned to be 1G
0, zero-length contacts of width with one, two, and three atoms, were observed under a force of 4–5 nN with a count ratio of 27, 60, and 13%, respectively. It was demonstrated that several types of contacts exhibit the same conductance at the quantized levels.
Evaluation of Linear Thermal Expansion Coefficients of Perovskite Oxides Using Ab-initio Molecular Dynamics with Small Cell Sizes for Materials Design
Authors: Tsuru Yusuke , Shimazu Megumi , Shiono Mitsunobu , Morinaga Masahiko
Published: April 2010

Calculations of linear thermal expansion coefficients have been carried out using ab-initio molecular dynamics with a small cell containing only ten atoms, which is a suitable cell size for materials design. The perovskite oxides of SrTiO3, BaZrO3, LaNiO3, CMgO3, CCaO3, and LaCoO3 were selected as the reference materials for comparison between calculated and experimental values. The calculated lattice constants were in good agreement with the experimental values. The thermal expansion coefficients of the six oxides, including LaCoO3 in the complex spin state, were evaluated from the temperature dependence of the lattice constants. There was reasonable agreement between the calculated and experimental values. Our results clearly proved that it is possible to obtain linear thermal expansion coefficients by ab-initio molecular dynamics, even with the use of a small cell for the calculations.
Optical and Mechanical Characterization of Chemical Mechanical Planarization Pad Surfaces
Authors: Sun Ting , Zhuang Yun , Borucki Leonard , Philipossian Ara
Published: April 2010

Both contact and non-contact methods are used to analyze surface properties of three types of chemical mechanical planarization (CMP) pads: plain, X
Y grooved, and concentrically grooved. Optical interferometry is used to probe the pad surface without contact and to produce a surface height probability density function (PDF). The right hand contacting tail of the PDF is often found to be exponential for CMP pads and a decay length (λ) as a measure of pad surface abruptness can be extracted. An incremental loading device is developed and used to measure the pad surface mechanical response. A pad–wafer contact model based on Greenwood and Williamson theory is used to interpret the nonlinear features of the pad surface compression data, which, furthermore, enables independent calculation of λ from mechanical data. Surface abruptness (λ) extracted from both methods (optical and mechanical) is found to be consistent for all three types of pads. No significant difference is observed in the pad surface abruptness among the three types of pads.
Effect of Plasma Pretreatment on Fixed Charge at the Silicon Nitride/Silicon Interface
Authors: Takakura Tomoyuki , Imai Ryusuke , Okamoto Yasunari , Taniguchi Hiroshi
Published: April 2010

The effect of plasma treatment prior to hydrogenated amorphous silicon nitride (a-SiN:H) deposition on the a-SiN:H/Si interface was studied. NH3, NH3+N2, and NH3+H2 were used as source gases for plasma treatments. Nitridation of silicon surfaces after plasma treatment was observed by X-ray photoelectron spectroscopy (XPS). Fourier transform infrared spectroscopy (FTIR) measurement revealed that the stoichiometry of the thin nitrided layer varied depending on the source gas. After the plasma treatment and subsequent a-SiN:H deposition on the silicon substrate, capacitance–voltage (C–V) characteristics of the metal–insulator–semiconductor (MIS) structure were measured. As a result, it was found that the interface trap density (D
IT) of the plasma-treated sample decreased compared with that of the nontreated sample, whereas the type of source gas did not affect D
IT. On the other hand, flatband voltage (V
FB) of MIS structure shifted along with the type of source gas, and this phenomenon indicates that the fixed charge at the a-SiN:H/Si interface depends on the stoichiometry of the thin nitrided layer. Finally, the passivation effect of plasma treatment was evaluated quantitatively on the basis of the extended Shockley–Read–Hall (SRH) theory.
Possibility of Forming 18-nm-Pitch Ultrahigh Density Fine Dot Arrays for 2 Tbit/in.2Patterned Media Using 30-keV Electron Beam Lithography
Authors: Hosaka Sumio , Tanaka Yasunari , Shirai Masumi , Mohamad Zulfakri , Yin You
Published: April 2010

We studied the possibility of forming ultrahigh-density fine dot arrays using 30-keV electron beam (EB) drawing for 2 Tbit/in.2patterned media. We investigated the effects of calixarene resist thickness and exposure dosage on the drawing of dot arrays with a minimum pitch. We found that the 13-nm-thick calixarene resist was very suitable for forming resist dot arrays with a pitch of 20 nm. Furthermore, the allowable region of proper exposure dosage became narrow as the pitch decreased. It is clarified that there exists a minimum pitch of 18 nm in drawing ultrahigh density fine dot arrays with a 13-nm-thick resist.
Oxidized Al Film as an Insulation Layer in AlGaN/GaN Metal–Oxide–Semiconductor Heterostructure Field Effect Transistors
Authors: Gregušová Dagmar , Gaži Štefan , Sofer Zdeněk , Stoklas Roman , Dobročka Edmund , Mikulics Martin , Greguš Ján , Novák Jozef , Kordoš Peter
Published: April 2010

We report on the technology of a very thin oxidized Al sputtered film used for gate insulation and passivation in Al2O3/AlGaN/GaN metal–oxide–semiconductor heterostructure field-effect transistors (MOSHFETs). Their transport properties are presented. The MOSHFET with the Al2O3 layer had improved static output and transfer characteristics compared with the reference heterostructure field-effect transistors (HFETs): (1) their saturation drain current I
DS was ∼600 mA mm-1 at gate voltage V
G=1 V (HFETs with 2.5 µm gates had ∼430 mA mm-1); (2) their transconductance was 116–140 mS mm-1 (HFETs had ∼70 mS mm-1).
Analysis of Q-Value of Quartz-Crystal Tuning Fork by Use of Thermoelastic Coupling Equations Including an Effect of Thermal Radiation
Authors: Itoh Hideaki , Tamaki Yuhya
Published: April 2010

We investigated a method of predicting the actual Q-value of a quartz-crystal tuning fork on the basis of thermoelastic coupling equations by considering an effect of thermal radiation from the flexural vibrating arms of the tuning fork to the external environment. We developed the method of calculating the quartz-crystal tuning fork's Q-value by use of a new temperature distribution solution, indicating an intermediate situation between adiabatic and isothermal solutions by use of a parameter α1 (0 ≦α1 ≦1; isothermal solution is given at α1 = 0 and adiabatic solution is given at α1 = 1) for the coupled heat conduction equation without a thermal radiation term, which was adjusted so as to have almost the same curve as the approximated temperature distribution including the zero-order and first-order temperature distribution solutions of the coupled heat conduction equation with the thermal radiation term, given by the perturbation method. Our calculated Q-value was closer to the measured value for an etching-processed quartz-crystal tuning fork than that obtained by the coupled heat conduction equation without the thermal radiation term under an adiabatic boundary condition.
Transparent-Oxide–Semiconductor Based Top-Gate Self-Alignment Thin-Film Transistors
Authors: Yamagishi Akira , Naka Shigeki , Okada Hiroyuki
Published: April 2010

Top-gate self-aligned transparent-oxide–semiconductor transistors with indium–zinc-oxide as a semiconductor have been studied. During transistor fabrication, successive sputtering of oxide semiconductor and insulator without breaking the vacuum can be realized owing to the transparency of oxide semiconductor. The overlapping length between the gate–source and gate–drain electrodes was as small as 0.7 µm. The obtained field-effect mobility, on–off ratio, threshold voltage, mutual conductance, and subthreshold slope were 30 cm2 V-1 s-1, 105, -3 V, 2 mS/mm, and 0.7 V/decade, respectively.
Fabrication of a Calibration Scale for Biological Fluorescence Microscopy Using Nano Imprinting
Authors: Iketaki Yoshinori
Published: April 2010

Using nano imprinting technology, a scale tool was fabricated for evaluating image properties of a biological fluorescence microscope. Evaluation of the properties given by a laser scanning microscope could be demonstrated. On this scale, a minute scale pattern with 100 nm structure could be transcribed on the usual type of cover glass with a dyed resist. This fabrication technique can provide a disposable scale tool at a low cost, which is very suitable for calibrating the optical performance given by novel microscopy as well as the conventional one.
Production of Size-Controlled Nanoscopic Cap-Shaped Metal Shells
Authors: Kim Hyonchol , Takei Hiroyuki , Yasuda Kenji
Published: April 2010

A method of producing precisely size-controlled metal nanoparticles is described. Polystyrene (PS) spheres placed on a substrate were used as a cast for the metal nanoparticles. The diameters of the PS spheres were processed into the desired sizes by oxygen plasma etching, and metal was deposited on the PS to the desired thickness by thermal evaporation. The PS casts were then removed by the UV-excited ozone oxidization reaction. The diameters of the obtained cap-shaped metal shells had a distribution within 5% of the coefficient of variation. These particles can be used as simultaneously applicable biological labels along with different-sized nanoparticles in immuno-electron microscopy.
Leakage Reduction by Thermal Annealing of NiPtSi Silicided Junctions and Anomalous Grain-Incompatible Pt Network
Authors: Tsuchiaki Masakatsu , Nishiyama Akira
Published: April 2010

Using highly reliable damage-free junctions, the effectiveness and limitation of Pt addition for the stabilization of thin NiSi films are accurately specified and practically formulated in terms of the thermally induced leakage. In addition to the thermal leakage, the unexpected emergence of initial leakage is also witnessed and attributed to the emission of Si interstitials during silicidation and the subsequent formation of boron interstitial clusters. Rapid evanescence of the initial leakage by post-annealing is also successfully demonstrated owing to the Pt-induced thermal stabilization. Moreover, unlike other Pt distributions considered so far, Pt atoms are revealed to concentrate in a distinctive manner, forming an anomalous in-layer web-like structure which even extends within single NiSi grains. This grain-incompatible Pt network is thought to be a remnant of Pt-aggregation around grain boundaries of an earlier metal-rich silicide phase (e.g., Ni2Si), incorporated and left intact in the final phase (i.e., NiSi). Such intermediate-phase Pt-rearrangement may have interfered with the phase transition sequence and reoriented the final NiSi grains to constitute a crystallographically stable and thermally robust interface structure, resulting in the effective stabilization by Pt addition.
Activation of B and As in Ultrashallow Junction During Millisecond Annealing Induced by Thermal Plasma Jet Irradiation
Authors: Matsumoto Kazuya , Higashi Seiichiro , Murakami Hideki , Miyazaki Seiichi
Published: April 2010

We have investigated effects of annealing temperature and heating and cooling rates during millisecond annealing on the activation of B and As in the Si lattice. In the case of As+-implanted samples, efficient dopant activation was observed at a temperature higher than 1000 K, while it was observed at a temperature higher than 1400 K in the case of B-implanted samples. The sheet resistance (R
S) of B-implanted samples monotonically decreases with temperature, and no significant dependence on heating rate (R
h) or cooling rate (R
c) is observed. On the other hand, As+-implanted samples show significant dependence of R
S on R
h and R
c. We have performed thermal plasma jet (TPJ) annealing on an As2
+-implanted sample, and obtained an ultrashallow junction (USJ) with a junction depth (X
j) of 11.9 nm and a R
S of 1095 Ω/sq. B USJ is also obtained with a X
j of 23.5 nm and a R
S of 392 Ω/sq. Precise control of R
h and R
c in addition to annealing temperature is quite important for achieving highly efficient doping in USJ.
Low Contact Resistivity with Low Silicide/p+-Silicon Schottky Barrier for High-Performance p-Channel Metal–Oxide–Silicon Field Effect Transistors
Authors: Tanaka Hiroaki , Isogai Tatsunori , Goto Tetsuya , Teramoto Akinobu , Sugawa Shigetoshi , Ohmi Tadahiro
Published: April 2010

A current drivability improvement of p-channel metal–oxide–silicon field effect transistors (MOSFETs) is necessary for the performance enhancement of complementary metal–oxide–semiconductor (CMOS) circuits. In this paper, we present the key technology for fabricating indispensable CMOS circuits with a small Schottky barrier height and a low contact resistance for p-type silicon using Pd2Si. We fabricated a Pd2Si gate Schottky barrier diode and a Kelvin pattern on silicon. The measured Schottky barrier height is 0.29 eV for p-type silicon. We also realized a very low contact resistivity of 3.7 ×10-9 Ω cm2 for the p+ region of silicon. The p-channel MOSFET with Pd2Si source/drain contacts realized a good characteristic, that is, a small off current. The technology developed in this work involves silicide formation for source/drain contacts of p-channel MOSFETs, which is expected to realize the performance enhancement of MOSFETs.
Thermal Stability of Nickel Silicide and Shallow Junction Electrical Characteristics with Carbon Ion Implantation
Authors: Tsui Bing-Yue , Lee Chen-Ming
Published: April 2010

In this work, we investigated the impact of carbon ion implantation on the thermal stability of nickel silicide film and nickel-silicide-contact n+/p shallow junctions. A higher carbon ion implantation dose can prevent the nickel silicide film from agglomeration and phase transformation. However, good thermal stability does not necessarily lead to excellent junction current–voltage characteristics owing to the diffusion of nickel atoms. When the carbon ion implantation dose increases to 5×1015 cm-2, many crystal defects are created. Then, numerous nickel atoms diffuse along these defects into the junction depletion region during the silicide formation process, resulting in poor junction characteristics. The trade-off between thermal stability and junction electrical characteristics is discussed in this paper. Finally, two methods are suggested to solve the serious leakage current problem.
Carbon Incorporation into Substitutional Silicon Site by Molecular Carbon Ion Implantation and Recrystallization Annealing as Stress Technique in n-Metal–Oxide–Semiconductor Field-Effect Transistor
Authors: Itokawa Hiroshi , Miyano Kiyotaka , Oshima Yasunori , Mizushima Ichiro , Suguro Kyoichi
Published: April 2010

Since the lattice constant of silicon-carbon (Si:C) is smaller than that of Si, Si:C embedded in the source and drain (e-Si:C S/D) can induce tensile stress in the channel and improve the electron mobility of n-metal–oxide–semiconductor field-effect transistor (nMOSFETs). In this research, molecular carbon (C) ion implantation and recrystallization schemes employed to achieve strained Si:C films with a high substitutionally incorporated carbon concentration ([C]sub) and a high ratio of substitution were studied. Several recrystallization techniques including rapid-thermal-annealing (RTA)-based solid phase epitaxy (SPE), spike annealing, and nonmelt laser annealing have been used to optimize C incorporation into Si and strain application. Results of these different implantation and annealing techniques are compared and discussed. Furthermore, we proposed the first recrystallization by nonmelt laser annealing and the co-incorporation of a dopant that increases the rate of Si regrowth and has a covalent radius slightly different from that of Si. These processes markedly promoted the recrystallization of C densely incorporated in an amorphous Si layer and improved the crystallinity of strained Si:C films while maintaining a high [C]subat a high ratio of substitution.
Contribution of Carbon to Activation and Diffusion of Boron in Silicon
Authors: Itokawa Hiroshi , Agatsuma Yuji , Aoki Nobutoshi , Uchitomi Naotaka , Mizushima Ichiro
Published: April 2010

It is well-known that the coimplantation of carbon (C) in a concentration range comparable to the range of boron (B) concentrations could suppress B diffusion, resulting in a boxlike B profile. Substitutional C atoms can capture excess self-interstitial Si atoms and suppress the diffusion of ion-implanted intersitial-type dopants such as B in silicon (Si). However, the effect of C on activation properties in wide C and B concentration ranges has not been sufficiently investigated. In this work, in the experiment in wide C and B concentration ranges, it was clarified for the first time that the B activation ratio of Si increases or decreases varies depending on the concentration of C incorporated. The activation ratio of the B activation layer was increased markedly by C incorporation in the case of light B implantation such as in the concentration range of 8×1019 to 3×1020 cm-3. This might be attributed to the interaction of C with Si interstitials and the suppression of the boron Si-interstitial clustering induced by C incorporation. In contrast, in the case of heavy B implantation such as at a 1×1021 cm-3 concentration, the activation ratio was decreased slightly by C incorporation. When stable B-containing clusters and precipitates were formed at high B concentrations, the effect of C incorporation on activation ratio was considered to be small.
High-Hole-Mobility Single-Crystalline Ge Thin Films Formed on Insulating Substrates by SiGe Mixing-Triggered Directional Melting Growth
Authors: Toko Kaoru , Tanaka Takanori , Sadoh Taizoh , Miyao Masanobu
Published: April 2010

The development of high-carrier-mobility Ge-channel thin-film transistors (TFTs) is desired to realize advanced system-in-displays. To achieve the development of single-crystalline Ge films on insulating substrates, we have developed the directional melting growth process of amorphous Ge by using polycrystalline Si islands as growth seeds. Defect-free single-crystalline Ge stripes of 400 µm length are realized, and high-hole-mobilities of more than 1000 cm2 V-1 s-1 are demonstrated in the entire lateral growth region. This method opens up the possibility of fabricating high-speed Ge-channel TFTs for system-in-displays.
The Role of High-κ TiHfO Gate Dielectric in Sputtered ZnO Thin-Film Transistors
Authors: Su Nai-Chao , Wang Shui-Jinn , Huang Chin-Chuan , Chen Yu-Han , Huang Hao-Yuan , Chiang Chen-Kuo , Wu Chien-Hung , Chin Albert
Published: April 2010

In this study, we demonstrate the role of a titanium hafnium oxide (TiHfO) gate dielectric in improving the overall electronic performance of a ZnO thin-film transistor (TFT). Ti
x
Hf1-x
O (x = 0.63) was fabricated by the rf co-sputtering technique. Using TiHfO as the gate dielectric, the device fabricated in this study exhibits a threshold voltage of 0.34 V, a subthreshold swing of 0.23 V/dec, a field-effect mobility of 2.1 cm2 V-1 s-1, and an ON/OFF current ratio of 105. The small subthreshold swing and low positive threshold voltage are attributed to the higher value of κ of 40 for the dielectric. This result enables device operation below 2 V, allowing its use in low-power driving circuits in display applications.
Threshold Voltage Tunability of p-Channel Metal Oxide Semiconductor Field-Effect Transistor with Ternary HfxMoyNz Metal Gate and Gd2O3 High-k Gate Dielectric
Authors: Peng Hsing-Kan , Lai Chao-Sung , Wang Jer-Chyi
Published: April 2010

p-channel metal oxide semiconductor field-effect transistor (pMOSFET) devices with a ternary Hf
x
Mo
y
N
z
metal gate and a Gd2O3 high-k gate dielectric have been demonstrated for the first time. The nitrogen-concentration-control method is a simple and cost-effective technique for metal work-function modulation. Hf
x
Mo
y
N
z
thin films were cosputtered from pure hafnium (Hf) and molybdenum (Mo) targets in nitrogen (N2) and argon (Ar) mixtures. The Hf
x
Mo
y
N
z
thin films have low resistivity and high thermal stability up to 950 °C. The threshold voltage (V
th) of the Hf
x
Mo
y
N
z
/Gd2O3 pMOSFET can be tuned from -0.6 to -0.08 V by controlling the nitrogen flow ratio. Moreover, there is little negative bias temperature instability (NBTI) degradation of the Hf
x
Mo
y
N
z
/Gd2O3 pMOSFET device. Compared with the Hf
x
Mo
y
N
z
/SiO2 pMOSFET, the Hf
x
Mo
y
N
z
/Gd2O3 pMOSFET has a small threshold voltage modulation owing to the extrinsic Fermi level effect at the Hf
x
Mo
y
N
z
and Gd2O3 interface. A physical model has been proposed to explain the extrinsic Fermi level pinning effect of the Hf
x
Mo
y
N
z
/Gd2O3 pMOSFET device.
Investigation of Thermal Stability of TiN Film Formed by Atomic Layer Deposition Using Tetrakis(dimethylamino)titanium Precursor for Metal-Gate Metal–Oxide–Semiconductor Field-Effect Transistor
Authors: Hayashida Tetsuro , Endo Kazuhiko , Liu Yongxun , Kamei Takahiro , Matsukawa Takashi , O'uchi Shin-ichi , Sakamoto Kunihiro , Tsukada Junichi , Ishikawa Yuki , Yamauchi Hiromi , Ogura Atsushi , Masahara Meishoku
Published: April 2010

In this paper, we describe the superiority of the titanium nitride (TiN) film formed by atomic layer deposition (ALD) using a tetrakis(dimethylamino)titanium (TDMAT) precursor for metal-gate electrodes of planar metal–oxide–semiconductor field-effect transistors (MOSFETs). It was demonstrated that the resistivity of the ALD TiN was significantly reduced by NH3 post deposition annealing (PDA). The electrical characteristics of the ALD-TiN-gate MOS capacitors and planar MOSFETs were evaluated and compared with those of the physical-vapor-deposited (PVD) TiN. The performance of the ALD-TiN-gate cases was confirmed to be superior to that of the PVD-TiN-gate cases, which was explained by the lower interface trap density (D
it) of the ALD TiN/SiO2 gate stack.
Atomic Layer Control for Suppressing Extrinsic Defects in Ultrathin SiON Gate Insulator of Advanced Complementary Metal–Oxide–Semiconductor Field-Effect Transistors
Authors: Shimamoto Satoshi , Kawashima Hiroshi , Kikuchi Toshiyuki , Yamaguchi Yasuo , Hiraiwa Atsushi
Published: April 2010

By measuring the minimum supply voltage for normal operation of test random access memories, we detected low-density extrinsic defects in silicon-oxynitride (SiON) gate insulators that were formed by state-of-the-art technologies. The density of the detected defects had a strong correlation with optical thickness d
opt, which was ellipsometrically measured, regardless of the processing conditions of the SiON films. We propose to maintain the d
opt above a threshold value of 1.7 nm to suppress the problems caused by the defects. The optimization of post nitridation annealing (PNA) condition is promising for meeting the criterion without sacrificing device performance. By elaborate investigations based on the Clausius–Mosotti relation, we found that the optical thickness of SiON films is approximately proportional to the atomic area density in the films. On the basis of this finding, we developed a model, which is an extension of the conventional analytical cell-based model, to figure out the physical process of the extrinsic-defect formation. The results analyzed using the model revealed that the extrinsic defects are formed in the SiON films in the case when the number of normal cells in a vertical arrangement becomes equal to or smaller than the threshold value of 3 or 4.
Evaluation of Anisotropic Biaxial Stress by Raman Spectroscopy with a High Numerical Aperture Immersion Objective Lens
Authors: Kosemura Daisuke , Takei Munehisa , Nagata Kohki , Akamatsu Hiroaki , Shimidzu Ryosuke , Ogura Atsushi
Published: April 2010

It is expected to be necessary to measure the stress tensors in Si because the stress field in the channels of metal–oxide–semiconductor field-effect transistors is remarkably complicated. Raman spectroscopy enables us to evaluate the stress precisely, nondestructively, and with relatively high spatial resolution, although its standard implementation fails to resolve the stress tensor. The goal of this study is to establish a procedure for measuring an unknown plane-stress state. In this study, the anisotropic biaxial stress in Si induced by a SiN film was evaluated by Raman spectroscopy with an immersion objective lens with a high numerical aperture.
Fabrication of Back-Side Illuminated Complementary Metal Oxide Semiconductor Image Sensor Using Compliant Bump
Authors: Watanabe Naoya , Tsunoda Isao , Takao Takayuki , Tanaka Koichiro , Asano Tanemasa
Published: April 2010

We fabricated a back-side illuminated (BSI) complementary metal oxide semiconductor (CMOS) image sensor in which a very-thin BSI photodiode array chip was stacked on a CMOS read-out circuit chip by compliant bumps. Cone-shaped bumps made of Au were prepared as the compliant bumps. The base diameter was 10–12 µm and the height was 9–10 µm. To fabricate the BSI CMOS image sensor, we developed a novel thin-chip assembly process. The key features of the process are as follows: preparation of a photodiode array wafer and a CMOS read-out circuit wafer, Au cone bump formation, bonding to support glass, thinning of the photodiode array wafer to 21 µm, through silicon via (TSV) formation using Cu electroplating, formation of back-side electrodes, transfer of the photodiode array wafer to a polymer support tape, dicing of the photodiode array wafer, separation of support tape, formation of Ni–Au bumps, dicing of CMOS read-out circuit wafer, and three-dimensional (3D) chip-stacking. The BSI CMOS image sensor thus fabricated has the following specifications: number of active pixels is 16,384 (128 ×128), photodiode size is approximately 18 µm square, photodiode pitch is 24 µm, and fill factor is approximately 55%. No defects were observed in the obtained image frames.
Nondestructive Warpage Measurements of LSI Chips in a Stacked System in Package by Using High-Energy X-ray Diffraction
Authors: Toda Akio , Ikarashi Nobuyuki
Published: April 2010

We describe high-energy X-ray diffraction to examine the warpage of packaged LSI chips nondestructively. Less absorption of the high-energy X-rays enables us to observe diffracted X-rays through packaging materials and LSI chips. We demonstrate that it is possible to measure the warpage of LSI chips in a stacked system in package (SiP). Although an LSI chip in a single-chip ball grid array (BGA) package simply warps into a convex-down shape, the LSI chips packaged in the BGA package as a stacked SiP warp into the shape of waves. It is inferred from results of our examination that the stress due to a printed circuit board substrate and molding resin affects chip warpage.
Hard-Mask-Through UV-Light-Induced Damage to Low-k Film during Plasma Process for Dual Damascene
Authors: Matsunaga Noriaki , Okumura Hirokatsu , Jinnai Butsurin , Samukawa Seiji
Published: April 2010

Plasma irradiation impact on a SiO2-hardmask/SiOCH low-k film stacked structure was investigated in detail. The plasma irradiation induces damage to the low-k film although it is covered by a hard mask. The hard-mask-through UV-light-induced damage showed plasma source gas dependence. The damage is determined by the UV light wavelength and photon energy. It was also found that a high substrate temperature accelerates the hard-mask-through UV-light-induced damage. The hard-mask-through UV-light-induced damage was hardly seen for the hard masks thicker than 115 nm in the O2-irradiation experiment. Conversely, an actual SiO2 film deposition process by plasma-enhanced chemical vapor deposition (PE-CVD) induces damage during deposition. The PE-CVD process induces heavier damage to the low-k film than the O2-plasma experiment. Higher process temperature accelerates the hard-mask-through UV-light-induced damage in the hard mask SiO2 deposition process.
Evaluation of Dielectric Constant through Direct Chemical Mechanical Planarization of Porous Low-k Film
Authors: Kodera Masako , Takahashi Takumi , Mimamihaba Gaku
Published: April 2010

Nanoporous materials are utilized in back end of line (BEOL) processing of current devices. However, their low k-values often alter during device fabrication such as plasma processing and/or wet treatment. In this study, we analyzed the effect of chemical mechanical planarization (CMP) slurries on k-values, and also evaluated three types of nanoporous low-k materials that were exposed to CMP slurries, dry processing, and/or barrier sputtering. We confirm that the k-value increase during direct CMP of porous low-k films is caused by the diffusion of surfactant through the films, depending on the characteristics of the nanoporous film and surfactant. The diffusion is explained by the adsorption of surfactant on sidewalls of continuous pores formed by porogen desorption while it is easily released by post-CMP annealing. In contrast, the increase in k-value during CMP after dry processing is mainly caused by moisture uptake.
Comparison of Lifetime Improvements in Electromigration between Ti Barrier Metal and Chemical Vapor Deposition Co Capping
Authors: Kakuhara Yumi , Yokogawa Shinji , Ueno Kazuyoshi
Published: April 2010

As promising technologies for fabrication of highly reliable Cu interconnects, using Ti barrier metal (Cu/Ti) and chemical vapor deposition (CVD) Co capping (Co/Cu/Ta/TaN) were compared. Both Cu interconnects similarly showed longer electromigration (EM) lifetime and larger activation energy of lifetime than conventional Cu interconnects fabricated using Ta/TaN barrier metal without capping metal (Cu/Ta/TaN). The residual resistance of Cu lines was measured cryogenically. Cu/Ti showed a higher residual resistance than Co/Cu/Ta/TaN and Cu/Ta/TaN, which indicates the presence of more impurities and a higher density of grain boundaries in Cu/Ti. Energy dispersive X-ray spectroscopy (EDX) analysis showed that a large amount of Ti doped into the Cu line segregated mostly at the grain boundaries on the Cu surface. It is suggested that Ti doped into a Cu line suppresses Cu diffusion through only the grain boundaries on the Cu surface. On the other hand, Co capping suppresses Cu diffusion through the entire Cu surface. As Cu/Ti improved EM lifetime significantly, the grain boundaries on the Cu surface are proposed to be a predominant diffusion path in EM. Since the density of grain boundaries probably increases on the Cu surface as interconnects shrink, suppressing the grain boundary diffusion on the Cu surface is highly effective to strengthen EM reliability.
Prediction of Abnormal Etching Profile in High-Aspect-Ratio Via/Hole Etching Using On-Wafer Monitoring System
Authors: Ohtake Hiroto , Fukuda Seiichi , Jinnai Butsurin , Tatsumi Tomohiko , Samukawa Seiji
Published: April 2010

For the prediction of abnormal etching profiles, an ion trajectory prediction system has recently been developed. In this system, sheath modeling was combined with the on-wafer monitoring technique for accurate prediction. This system revealed that sidewall conductivity strongly affects the charge accumulation and ion trajectory in high-aspect-ratio holes. It was also found that the accumulated charge in adjacent holes is one of the reasons for the generation of twisting profiles according to analysis using the system. We presume that the prediction system is an effective tool for developing nanoscale fabrication.