bluuebunny/crossref_metadata_2025 huggingface dataset:
Low-Voltage Cathodoluminescent Properties of Blue-Emitting Yttrium Silicates Doped With Cerium
Authors: Bosze E. J. , Hirata G. A. , Mckittrick J. , Shea L. E.
Published: April 2011

Yttrium silicate activated with Ce3+, (Y1−xCex)2SiO5, has been found to be an efficient phosphor that can potentially be used as the blue-emitting component in field emission flat panel displays. This highly refractory powder can be synthesized by combustion synthesis, a low cost technique used to fabricate multicomponent oxide powders in a single step process. The effect of activator concentration and post-synthesis annealing was examined on the fluorescent properties. The powders were found to be monoclinic space group P21/c in the as-synthesized state, and transformed to monoclinic space group C2/c after annealing. The maximum luminous emission intensity was reached after a one hour anneal at 1350°C for x=0.0075, with the peak Ce3+ emission wavelength between 420 and 450 nm. When co-doped with Gd3+, no increase in the emission intensity was observed.
Hillock Formation and Reduction Using Metal Interlayers for Active Matrix Display Applications
Authors: Saha Sambit K. , Howell Robert S. , Hatalis Miltiadis K.
Published: April 2011

The effects of using an extra layer of nickel, cobalt or titanium with Al-1%Cu films were examined with regard to hillock formation. The density and sizes of hillocks in these double layer metallization structures were characterized using scanning electron microscopy (SEM) and interfacial reactions between the transition metal layer and Al-l%Cu were examined using glancing angle x-ray diffraction (GA-XRD). Resistivities of the double layer films were characterized using conventional 4-point probe measurements. Hillock formation was totally suppressed when Ni and Co was used as the transition metal, while Ti did not eliminate hillocks. Hillock formation and resistivities are explained on the basis of interfacial reactions.
High Conductivity Gate Metallurgy for TFT/LCD's
Authors: Fryer Peter M. , Colgan E. , Galligan E. , Graham W. , Horton R. , Jenkins L. , John R. , Kuo Y. , Latzko K. , Libsch F. , Lien A. , Nywening R. , Polastre R. , Rothwell M. E. , Wilson J. , Wisnieff R. , Wright S.
Published: April 2011

Amorphous silicon based thin film transistor liquid crystal displays (TFT/LCD) have become the dominant technology used for flat panel displays for notebook computers. The need for higher resolution, larger diagonal displays for both notebook and desktop applications is discussed. Calculations have shown that the use of high conductivity gate metal such as aluminum or copper, together with the implementation of improved groundrules, can significantly extend today's technology. Aluminum suffers from problems with hillock formation during PECVD processing, and copper typically has poor adhesion to glass, reaction problems with silicon and other PECVD films, and difficulties in contacting it to other metals. Approaches to solving problems with both materials are presented, and a novel reduced mask process to fabricate high resolution, high aperture ratio 10.5” SXGA (1280 × 1024) displays is described. The process uses copper gate metallurgy with redundancy, without the need for extra processing steps. The resulting displays have 150 dpi color resolution, an aperture ratio of over 35%, and excellent image quality, making them the first high resolution displays that are suitable for notebook applications.
Boron Nitride Emitters
Authors: Pryor R. W. , Li Lihua , Minina G. , Busta H. H.
Published: April 2011

New observations are presented on the emission of electrons from n-type boron nitride (BN) cold cathode films. These carbon-doped BN films demonstrate a significant improvement in the electron emission current, on the order of 1 to 3 orders of magnitude, as a function of the extraction field for many different materials and morphologies.

These BN cold cathodes have yielded stable DC currents in excess of 4 mA at an extraction field of approximately 30 V/μm.
Emission and Processing Requirements for Carbide Films on Mo Field Emitters
Authors: Mackie W. A. , Xie Tianbao , Matthews M.R. , Davis P. R.
Published: April 2011

We have been working for many years on electron emission and surface properties of transition metal carbides. These studies have covered field, photo, and thermionic emission from bulk carbides as well as field and photo emission from carbide coatings and films on various substrates. Thin film carbide overcoatings have also been used on field emitter arrays of both Mo and Si. These unique carbide materials have electron emission properties making them attractive candidates for several applications. Uses for these carbides include FEA video displays, microwave applications, high current and small spot electron sources (e.g. accelerators and FELs), and cold cathodes for operation at tube pressures and in poor vacuums (e.g. FEAs, vacuum detectors, and neutralizing beams for ion thrusters).

We report here on one aspect of our current research which deals with electron emission of ZrC films coating single Mo field emitters. The relevant application is Spindt-type field emitter arrays. Processing steps are evaluated showing the need for a clean substrate. After deposition treatments are also investigated. Emission degradation has been noted after exposure to air and we report on successful use of a hydrogen atmosphere to reverse those adverse effects.
Characteristics of Surface-Emitting Cold Cathode Based on Porous Polysilicon
Authors: Komoda Takuya , Sheng Xia , Koshida Nobuyoshi
Published: April 2011

It is demonstrated that porous polysilicon (PPS) diode fabricated on the silicon substrate operates as efficient and stable surface-emitting cold cathode. A 1.5 pm of non-doped polysilicon layer is formed on n-type (100) silicon wafer and anodised in a solution of HF(50%): ethanol = 1:1 at a current density of 10 mA/cm2 for 30 seconds under illumination by a 500W tungsten lamp from a distance of 20 cm. Subsequently, PPS layer is oxidized in a rapid thermal oxidation(RTO) furnace for one hour at a temperature of 700°C. A semi-transparent thin Au film (about 10 nm thick) is deposited onto the PPS layer as a positive electrode and an ohmic contact is formed at the back of the silicon wafer as a negative electrode. When a positive bias is applied to the Au electrode in vacuum, the diode uniformly emits electrons. No electron emission is observed in the negatively biased region. Emission current is about 10−4 A/cm2 at 20V bias, and no fluctuation of emission current is observed as a function of time. Emission current is not affected by a surrounding pressure up to around 10 Pa. It is envisaged that mechanism of this emission is attributed to hot electron tunnelling.
Field Emission from Low Temperature Carbon Coated Silicon Tips
Authors: Kosarev A.I. , Zhirnov V.V. , Vinogradov A.J. , Shutov M.V. , Bormatova L.V. , Givargizov E.I. , Felter T.E.
Published: April 2011

Field emission from silicon tips with carbon coatings deposited by VHF CVD at low temperature, Ts=225°C, has been studied. Emission was measured from both single tips and tip arrays. Structure and electronic properties of the films have been characterized. Significant effects due to pregrowth plasma treatment of the sample surface were observed on microstructure and emission characteristics. Optimized carbon coatings on silicon tips increased emission current by about two orders and reduced the threshold field to 0.1 V/μm.
New Lateral Field Emitter Arrays Inherently Integrated with Thin Film Transistor
Authors: Lim Moo-Sup , Park Cheol-Min , Han Min-Koo , Choi Yearn-Ik
Published: April 2011

Abstarct

We have fabricated a new three-terminal lateral field emitter structure in which the anode current is limited by the channel current of undoped region. The new device exhibits an excellent stability of the emission current. The field emission characteristics of fabricated device have two modes. In the first mode below 89 V, the mechanism of emission is identical to that of conventional poly-Si emitters and, in the second mode above 89 V, the emission current is limited by the inversion charges in the channel, so stable anode current is maintained. Furthermore, the fabrication process of the device is very simple.
Dielectric Properties of Glass Capillary Arrays
Authors: Huber T. E. , Silber Leo , Boccuzzi Frank
Published: April 2011

Glass Capillary Arrays (GCA) are low density columnar monolithic structures made of soda-lime glass. This structure, in which 76% of volume between the columns, the channels, is void, also has a greatly reduced dielectric constant in comparison with bulk glass. We have measured the index of refraction and absorption of samples of GCA's in the X-band, 8 × 109 Hz to 1.2×1010 Hz, for various orientations of the channels with respect to the polarization. For channels perpendicular to the polarization direction we have measured an index of refraction of 1.15. In comparison the index of refraction of (bulk) soda-lime glass is 2.6. We also examined the absorption in the far-infrared (FIR) frequency range between 6×1011 Hz and 6×1012 Hz. In this frequency range we obtain a k2 dependence due to losses in the glass matrix at higher frequencies. The results of the X-band and FIR results are interpreted in terms of an effective medium theory of the real and imaginary part of the dielectric constant of the composite.
Integration Issues for Diamond Like Carbon in a Copper Damascene Process Flow
Authors: Grill A. , Jahnes C. , Patel V. , Ott J. , Hummel J. , Mih R. , Liu J.
Published: April 2011

Hydrogenated “diamondlike” carbon (DLC) is a potential candidate as a low k material for the back end interconnect (BEOL) dielectric for VLSI chips. The DLC material is an attractive dielectric due to its isotropic properties and the ability to deposit the films by CVD techniques, such as PECVD or HDP systems. Under suitable preparation conditions such materials can reach dielectric constant values below 2.8, even as low as 2.4. While the as-deposited films are not stable to exposure to subsequent processing temperatures of about 400 C, it appears that they can be stabilized, in terms of dimensional stability and material loss, by an initial anneal.

The integration of DLC films in the BEOL structure further requires good adhesion with the materials in contact with the DLC dielectric, such as silicon nitride or silicon oxide, and liner metallurgy. As the potential application of the DLC films will be in Cu based damascene structures the behavior of the films under CMP conditions is also important.

The talk will discuss the evaluation of DLC films and of integration issues such as adhesion under processing conditions, patterning, CMP behavior. Blanket and patterned structures built with DLC films will be presented.
Copper damascene using low dielectric constant fluorinated amorphous carbon interlayer
Authors: Matsubara Y. , Endo K. , Iguchi M. , Ito N. , Aoyama K. , Tatsumj T. , Horiuchi T.
Published: April 2011

We have developed a new interconnect technique using a low-k (εt,=2.5) organic interlayer (fluorinated amorphous carbon: a-C:F) and a low-resistivity metal line (copper). The new technique attains a duction in both the capacitance of the interlayer and the resistance of the metal line. We found that a-C:F on Cu reduces reflection to 10% for Kr-F line lithography. However, a-C:F cannot act as a protection layer for oxidation even at 200°C in atmospheric ambient annealing. Cu diffusion into a-C:F is about 100 nm at the annealing temperature of 450°C. The resistivity of the Cu line is 2.3–2.4 μΩ · cm for the 0.5-μm line width. Although the leakage current of the a-C:F ILD is one order higher than that of the SiO2 ILD, electrical isolation is acceptable at < 20 V when annealing is carried out at 350°C in a vacuum.
Stability Of Silicon-Oxygen-Fluorine And Carbon-Fluorine LOW-K DIELECTRICS WITH RESPECT TO ATTACK BY WATER
Authors: Yang H. , Lucovsky G.
Published: April 2011

Ab initio configuration interaction calculations have been previously used to account for the relatively large decreases in the static dielectric constant of Si-O-F alloys with low alloy concentrations of F-atoms, ∼ 22%for F concentrations of ∼ 10 at.%. The present study addresses the stability of these alloy films and carbon-fluorine films with respect to attack of Si-F bonds or C-F bonds by water molecules. The present calculations show that the reaction: H20 + 2 Si-F - 2 HF + Si-O-Si is exothermic by about 0.7 eV. However, the reaction of H20 + 2 C-F - 2 HF + CO-C is calculated to be endothermic by 1.6 eV. Our calculations focus on the reaction energetics and geometries as a function of the distance between the F-atoms of the Si-F and C-F groups and water molecule.
Experimental and Theoretical Study of Structure-Dielectric Property Relationships for Polysilsesquioxanes
Authors: Kim Sung Mog , Yoon Do Y. , Nguyen Cattien V. , Han Jie , Jaffe Richard L.
Published: April 2011

Structures of polysilsesquioxanes {(R- SiO1.5)n with R=H, CH3, C6H5} in spin-on thin films are investigated in relation to their dielectric properties. IR spectroscopy in combination with results from quantum chemistry calculations shows that the initial hydrido-silsesquioxane films (cured to 250 °C) exhibit more symmetric ring structures than those for methyl-silsesquioxanes. Moreover, IR spectra indicate that increasing the cure temperature above a critical value, which varies with the Si-R moiety, causes extensive three-dimensional cross-linking in silsesquioxanes via breakage of the Si-R bond and formation of networks of O-Si-O structures with a lower ring symmetry than the initial materials. Dielectric properties do not appear to vary with the structural symmetry about the O-Si-O moiety nor with the R substituents, but rather depend on the extent of three-dimensional cross-linking as seen by the loss of Si-R absorbance. Highly cross-linked silsesquioxanes show a higher dielectric value and no variation with temperature from −100 °C to 150°C range, whereas a lower value and a negative temperature dependence are seen for dielectric constants of silsesquioxane samples with little loss of Si-R absorbance.
5.5 kV Bipolar Diodes From High Quality CVD 411-SiC
Authors: Irvine K. G. , Singh R. , Paisley M. J. , Palmour J. W. , Kordina O. , Carter C. H.
Published: April 2011

Thick, high quality 4H-SiC material suitable for high power devices has been grown in a hot-wall reactor. Recent improvements to the growth process have improved our thickness uniformity over a 50mm wafer to less than 1% and the doping uniformity to less than 5%, both values expressed as σ/mean.

A record breaking reverse blocking voltage of 5.5 kV was obtained on P-i-N diodes fabricated from a 85μm thick film. The on-state voltage drop was 5.4 V at 100 A/cm2. From this on-state voltage drop, the carrier lifetime was estimated in excess of 1μs.
Silicon Carbide Epitaxial Layers Grown ON SiC Wafers With Reduced Micropipe Density
Authors: Rendakova S. , Kuznetsov N. , Savkina N. , Rastegaeva M. , Andreev A. , Minbaeva M. , Morozov A. , Dmitriev V.
Published: April 2011

The characteristics of SiC high-power devices are currently limited by the small area of the devices, which is usually less than 1 sq. mm. In order to increase device area, defect density in SiC epitaxial structures must be reduced. In this paper, we describe properties of silicon carbide epitaxial layers grown on 4H-SiC wafers with reduced micropipe density. These layers were grown by the vacuum sublimation method. Large area Schottky barriers (up to 8 mm2) were fabricated on SiC epitaxial layers and characterized.
Temperature Dependence of Breakdown Field in p-π-n GaN Diodes
Authors: Osinsky A. , Shur M. S. , Gaska R.
Published: April 2011

We present the results of the study of the electric breakdown in p-π-n GaN diodes. The breakdown is observed at reverse biases above 40 V and is accompanied by the formation of microplasmas. The study shows that the observed breakdown field in GaN (on the order of 1 to 2 MV/cm) increases with the temperature. This feature makes GaN very promising for high power devices and avalanche photodetectors, operating at elevated temperatures.
Investigation Of Microplasma Breakdown In 4H Silicon Carbide
Authors: Zimmermann Uwe , Hallén Anders , Konstantinov Andrey O. , Breitholtz Bo
Published: April 2011

Reverse bias breakdown behaviour of high quality 4H silicon carbide p-n diodes was investigated, using optical and electrical measurement techniques. Most of the sample diodes suffered from early breakdown phenomena in the form of microplasmas at about 80% of the calculated parallel plane breakdown voltage for the diodes, as evident from measured I-V curves. A group of these microplasmas could be correlated to micropipes, identified by optical microscopy, while a large number of microplasmas were caused by other defects and inhomogenities in the space charge region under reverse bias. The same spots that revealed early breakdown phenomena under reverse bias also showed a different electroluminescence (EL) behaviour under low forward current densities compared to those areas with a homogeneous breakdown behaviour. However, even diodes containing one or more micropipes in the region of the junction showed good rectifying behaviour up to two third of the parallel plane breakdown voltage, where the turn-on of a microplasma was observed.
Scandium And Gallium Implantation Doping Of Silicon Carbide
Authors: Henkel T. , Tanaka Y. , Kobayashi N. , Koutzarov I. , Okumura H. , Yoshida S. , Ohshima T.
Published: April 2011

Rutherford backscattering, Raman spectroscopy as well as photoluminescence, resistivity and Hall measurements have been used to investigate the doping behaviour of Scandium and Gallium ions implanted into Silicon Carbide respectively. The recovery of the crystal lattice after implantation at room temperature followed by rapid thermal annealing is shown to be less effective in the case of Scandium compared with Gallium. Scandium implanted SiC exhibited a high resistivity in comparison to Gallium implanted crystals.
The Magnitude of the Piezoelectric Effect in InGaN Quantum Wells
Authors: Perlin Piotr , Kisielowski Christian , Mattos Laila , Shapiro Noad A. , Kruger Joachim , Yang Jinwei , Weber Eicke R.
Published: April 2011

A photoluminescence from a multiquantum GaN/InxGa1−xN/GaN well structure (x varies between 0.1 to 0.4) was investigated at various temperatures, pumping powers. While the temperature dependence of the peak position indicates normal band to band character of radiative recombination, the large pumping power induced “blue”shift of the peak position (up to 200 meV) can be observed. This kind of shift cannot be easily explained by the band tailing effect but is most likely the result of the screening of the strain-induced piezoelectric field. By evaluating the theoretical values of the piezoelectric filelds in the quantum well, we can show that in order to account for the experimental results we have to assume the partial relaxation of the strain.
Role of Nanopipes in Degradation of AlGaN/InGaN/GaN Devices Operating at High Voltage
Authors: Osiński Marek , Lee Jinhyun , Barton Daniel L.
Published: April 2011

We argue that the nanopipes recently observed in device-quality GaN grown on sapphire play an important role in degradation of nitride-based devices requiring high driving voltage, such as diode lasers or high-power electronics. The nanopipes offer a preferential path for the top (p-side) contact metal to migrate down towards the p-n junction under high-voltage operation, eventually causing a short and device failure. The metal migration process is enhanced by high voltage (tens of volts) required to drive high-current pulses through the device, and its elimination is of critical importance for achieving reliable GaN-based power devices and diode lasers.
Nitride Based High Power Devices: Transport Properties, Linear Defects And Goals
Authors: Bandić Z. Z. , Bridger P. M. , Piquette E. C. , Beach R. A. , Phanse V. M. , Vaudo R. P. , Redwing J. , McGill T. C.
Published: April 2011

The wide bandgap semiconductors GaN and AlGaN show promise for high voltage standoff layers in high power devices such as GaN Schottky rectifiers and GaN/AlGaN thyristorlike switches. The material properties which significantly influence the device design and performance are electron and hole diffusion lengths, recombination lifetimes and the critical field for electric breakdown. We have fabricated high standoff voltage (> 450 V) GaN Schot-tky rectifiers, and measured a lower limit for the critical field for electric breakdown to be (2 ± 0.5) · 106 V/cm. Diffusion lengths and recombination lifetimes were measured by electron beam induced current on unintentionally doped, n and p-type GaN samples grown by various epitaxial techniques. To establish the possible effects of linear dislocations and other defects on the transport and breakdown properties, the same sample surfaces were analyzed by AFM. On some of the samples, our measurements indicate that the dislocations appear to be electrically active and that recombination at dislocations occupying grain boundaries limit the minority carrier lifetime to the nanosecond range. Based on the measurements of transport properties, critical fields and the modeling of the devices proposed, our estimates indicate that DARPA/EPRI goals for megawatt electronics set at 5 kV standoff voltage and 200 A on-state current might be achieved with 15 – 20 μm thick layers grown by HVPE, at approximately 1. 1016 cm−3 doping levels, and 1 – 2cm2 device active area.
High Resolution X-ray Diffraction and X-ray Topography Study of Gan on A12O3
Authors: Chaudhuri J. , Ng M. Hooe , Koleske D. D. , Wickenden A. E. , Henry R. L.
Published: April 2011

High resolution x-ray diffraction and x-ray topography study of GaN thin films, grown on sapphire (00.1) substrate by reduced pressure metalorganic vapor phase epitaxy under various conditions, were performed. An attempt was made to correlate the mobility in films with similar carrier concentration with the strain and dislocation density. X-ray topography revealed the defects present in the film.
Correlation Between Oxide Breakdown And Defects In Sic Wafers
Authors: Soloviev S. , Khlebnikov I. , Madangarli V. , Sudarshan T. S.
Published: April 2011

A correlation between gate oxide breakdown in MOS capacitor structures and structural defects in SiC wafers is reported. The oxide breakdown under high applied fields, in the accumulation regime of the MOS capacitor structure, is observed to occur at locations corresponding to the edge of bulk structural defects in the SiC wafer such as polytype inclusions, regions of crystallographic mis-orientation, or different doping concentration. Breakdown measurements on more than 50 different MOS structures did not indicate any failure of the oxide exactly above a micropipe. The scatter in the oxide breakdown field across a 10mm × 10mm square area was about 50%, and the highest breakdown field obtained was close to 8 MV/cm.
Direct Growth of AIN Thin Layer on (111)Si Substrate by RF-MBE
Authors: Ohshima Naoki , Yonezu Hiroo , Uesugi Shinobu , Gotoh Keisuke , Yamahira Seiji
Published: April 2011

The nitridation process of (111)Si surface has been studied by in-situ reflection high-energy electron diffraction (RHEED) and Auger electron spectroscopy (AES) measurements. It has been clarified that the nitridation of the Si surface is occurred even if the shutter of the discharged rf-plasma gun is closed. The growth process of AIN epilayer on the Si substrate by migration enhanced epitaxy (MEE) has been investigated by in-situ RHEED and atomic force microscopy (AFM) observations. It has been found that the AIN epilayer is directly grown on (111)Si by MEE growth.
High Energy Implantation of Boron in 4H-SiC
Authors: Schönerl Adolf , Karlsson Stefan , Schmitt Thomas , Hallén Anders , Frischholz Manfred , Rottner Kurt
Published: April 2011

The high energy implantation of boron into n-type Silicon Carbide epitaxial layers of the polytype 4H was investigated for various sample temperatures during implantation and different doping concentrations. Depth profiling using secondary ion mass spectrometry was applied to determine the boron distribution in the as-implanted epilayers and the re-distribution of boron atoms during a half hour heat treatment at a temperature of 1700 °C. The SIMS boron profiles are compared to numerical Monte Carlo calculations using the program TRIM96 and to electrical profiling by scanning capacitance microscopy.

In general we found that boron is moving towards the implantation damage already during the implantation of a profile with four different energies. The defect enhanced diffusion of boron is more pronounced during the high temperature anneal, where a higher concentration of boron diffusing towards the sample surface was observed. Into the bulk of the epilayer the boron diffusion is on a lower level and shows an exponential decay with a length of up to 5 Pm. An out-diffusion of boron during the post implantation anneal was not observed at implantation temperatures up to 500 °C.

Electrical profiling using scanning capacitance microscopy revealed that complicated layer structures with several pn-junctions can occur due to the re-distribution of boron during post implantation anneal.
Dry Etching Damage Effect on Ohmic Characteristics of GaN
Authors: Khim Jin Seok , Kim Taek , Chae Su Hee , Kim Tae Il , Kim Hyon-Soo , Yeom Geun-Young
Published: April 2011

We report on the dry etching damage effects on the Ohmic contact characteristics of Sidoped n-type GaN. The 2-µm thick n-type GaN samples whose carrier concentrations are ∼7 × 1017/cm3 are grown on c-plane sapphire substrates by metalorganic chemical vapor deposition(MOCVD). The samples are processed to measure the transmission line method(TLM). We evaporated Ti/Al/Ni/Au=150/2700/400/4000 Å on the samples using an ebeam evaporator under 5 × 10−7 torr and annealed at 700 °C for lminute using a rapid thermal annealer(RTA). AES and XPS data show that the surface stoichiometry of the sample etched with H2 gas is gallium- richer than that of the one etched with Cl2 gas. According to the previous report[l], N-vacancy acts as shallow donor in GaN. However, specific contact resistivity of the sample etched with H2 gas is 3.03 × 10−6 Ω cm 2, which is much higher than that of the sample etched with C12 gas, 7.9 × 10 −7 Ω cm2. The difference of the N- vacancy formed during the etching process cannot completely explain the result. We suggest that formation of GaxOy during etching process, and the weakening of the bonding by ion bombardments might be responsible for the difference in the ohmic characteristics.
Comparison of Novel Chlorine, Bromine and Iodine Plasma Chemistries for Anisotropic Trench Etching In GaN, InN and Ain
Authors: Cho Hyun , Maeda T. , MacKenzie J. D. , Donovan S. M. , Abemathy C. R. , Pearton S. J. , Shul R. J. , Han J. , Ren F.
Published: April 2011

Anisotropic pattern transfer has been performed for GaN, InN and AIN in Cl2/Ar, BI3/Ar and BBr3/Ar Inductively Coupled Plasmas(ICP). Controlled etch rates in the range of 500–1500Å·min−1 are obtained for III-nitride materials in Cl2/Ar chemistry. Etch selectivities of 100:1 were achieved for InN over both GaN and AIN in the BI3 mixtures, while for BBr3 discharges values of 100:1 for InN over AIN and 25:1 for InN over GaN were measured.
Low Bias Dry Etching of Sic and Sicn in ICP NF3 Discharges
Authors: Wang J. J. , Cho Hyun , Lambers E. S. , Peartont S. J. , Ostling M. , Zetterling C.-M. , Grow J.M. , Ren F. , Shul R. J. , Han J.
Published: April 2011

A parametric study of the etching characteristics of 6H p+ and n+ SiC and thin film SiC0.8N0.2 in Inductively Coupled Plasma NF3/O2 and NF3/Ar discharges has been performed. The etch rates in both chemistries increase monotonically with NF3 percentage and rf chuck power reaching 3500Å·min−1 for SiC and 7500 Å·min−1 for SiCN. The etch rates go through a maximum with increasing ICP source power, which is explained by a trade-off between the increasing ion flux and the decreasing ion energy. The anisotropy of the etched features is also a function of ion flux, ion energy and atomic fluorine neutral concentration. Indium-tinoxide( ITO) masks display relatively good etch selectivity over SiC(maximum of 70:1) while photoresist etches more rapidly than SiC. The surface roughness of SiC is essentially independent of plasma composition for NF3/O2 discharges, while extensive surface degradation occurs for SiCN under high NF3:O2 conditions. The high ion flux available in the ICP tool allows etching even at very low dc self-biases, ≤ −10V, leading to very low damage pattern transfer.
Effect of V/III Ratio on the Properties of GaN Layers Grown by Molecular Beam Epitaxy Using NH3
Authors: Grandjean N. , Leroux M. , Massies J. , Mesrine M. , Lorenzini P.
Published: April 2011

Ammonia as nitrogen precursor has been used to grow III-V nitrides by molecular beam epitaxy (MBE) on c-plane sapphire substrates. The efficiency of NH3 has been evaluated allowing the determination of the actual V/III flux ratio used during the GaN growth. The effects of the V/III ratio variation on the GaN layer properties have been investigated by photoluminescence (PL), Hall measurements, atomic force microscopy (AFM), and secondary ion mass spectroscopy (SIMS). It is found that a high V/III ratio leads to the best material quality. Optimized GaN thick buffer layers have been used to grow GaN/AlGaN quantum well (QW) heterostructures. Their PL spectra exhibit well resolved emission peaks for QW thicknesses varying from 3 to 15 monolayers. From the variation of the QW energies as a function of well width, a piezoelectric field of 450 kV/cm is deduced.
Pulsed-Field-Gradient NMR Studies of Hydrogen Diffusion in Laves-Phase Hydrides
Authors: Majer G.
Published: April 2011

The diffusivities D of hydrogen in cubic Laves-phase hydrides have been measured by means of pulsed-field-gradient nuclear magnetic resonance over wide temperature ranges. A review is given of the diffusion coefficients of hydrogen in ZrCr2Hx, rTi2Hx, ZrV2Hx, ZrMo2Hx. and HfV2Hx. with special emphasis on the variation of D with the hydrogen concentration x. The formation of ordered low-temperature phases in ZrV2Hx results in a substantial reduction of the hydrogen diffusivity. The dependence of D on the lattice parameter of the host compound is considered.
Hydrogen Motion In Lanthanum Hydrides By Means Of Quasielastic Neutron Scattering
Authors: Karmonik C. , Udovic T. J. , Rush J. J.
Published: April 2011

The hydrogen dynamics in LaHx was studied for different concentrations x ≥ 2.5 at different temperatures by quasielastic neutron scattering. The neutron spectra show the existence of both long-range translational diffusion and localized motion. The prefactor of the jump rate for the first process exhibits a maximum around x= 2.75. The radius for the second motion is in agreement with neutron powder diffraction measurements which support a localized motion of H confined in an octahedral site.
Hydrogen Migration In Phosphorous Doped Polycrystalline Silicon
Authors: Nickel N. H. , Kaiser I.
Published: April 2011

Hydrogen diffusion in phosphorous doped polycrystalline silicon was investigated by deuterium diffusion experiments. The presence of phosphorous enhances hydrogen diffusion. For high hydrogen concentrations the activation energy of the effective diffusion-coefficient amounts to 0.25-0.35 eV. At low hydrogen concentrations diffusion is governed by deep traps that are present in an appreciable concentration of 6×108 - 1019 cm−3. The hydrogen chemical-potential, 9H, decreases with increasing temperature at a rate of ˜ 0.002 eV/K. The data are discussed in terms of a two-level model used to describe hydrogen diffusion in amorphous and undoped polycrystalline silicon.
Microscopic Study Of The Hydrogen Diffusion In III-V Semiconductors
Authors: Burchard A. , Deicher M. , Forkel-Wirth D. , Knopf M. , Magerle R. , STötzler A. , Fedoseyev V. N. , Mishin V. I. , Isolde-Collaboration The
Published: April 2011

We report on experiments which observe on a microscopic scale the migration of isolated hydrogen in InP, GaAs, and InAs. Using the radioactive acceptor 117Cd, Cd-H pairs have been formed in these III-V semiconductors. After the decay of 117Cd to 117In, H is no longer bound to an acceptor and can diffuse freely. This diffusion has been observed by perturbed yy angular correlation (PAC) spectroscopy. At 10 K, the occupation of two different lattice sites by hydrogen has been observed. First results on the diffusion of hydrogen will be discussed.
Annealing Behavior of the Hydrogen-Vacancy Complex in Bulk Indium Phosphide Crystals
Authors: Ye Q. , Wolk J. A. , Bourret-Courchesne E. D. , Bliss D. F.
Published: April 2011

In order to explain the effects of hydrogen on the electrical properties of bulk indium phosphide crystals, we have performed a series of high temperature annealing studies with both undoped and iron-doped indium phosphide crystals. Our samples were annealed at 900°C for 6, 36, and 72 hours, respectively, under a phosphorus overpressure of five atmospheres. Samples were characterized at 10 K by Fourier transform infrared absorption spectroscopy which allowed us to measure the concentrations of both the Fe2+ and VIn-H4 defects simultaneously. Undoped samples were further characterized by the Hall effect measurements. We find in the iron-doped samples that the [Fe2+]/[Fe3+] ratio decreases gradually with increasing annealing time, indicating a reduction in the number of donors in the samples. In the undoped samples, annealing leads to a reduction of the free electron concentration accompanied by an increase in the 77 K mobility. The increase of the sample's mobility eliminates the possibility that the reduction of the free electron concentration is due to an increase in the concentration of the compensating acceptors. Our explanation for the observed behavior in all samples is that hydrogen acts as a donor and it diffuses out of the crystal during the annealing process. Based on our experimental data, we propose a calibration equation of [VIn-H4] = 4.2×1016 cm−1 × Absorbance (cm−1) which is used to correlate the hydrogen-vacancy complex concentrations with the changes of the VIn-H4 absorption peak in both the iron-doped and the undoped samples. Our results confirm the donor nature of the hydrogen-vacancy complex and provide strong evidence regarding the reduction mechanism of free carrier concentrations in bulk indium phosphide crystals during high temperature annealing under a phosphorus atmosphere.
An Alternative Approach for Modeling the Hot Carrier Degradation of the Si/SiO2 Interface
Authors: Chen Zhi , Lee Jinju , Lyding Joseph W.
Published: April 2011

An alternative approach for modeling the hot carrier degradation of the Si/SiO2 interface based on the dispersive characteristics of the interface trap generation has been proposed. The timedependent interface trap generation has been modeled using the stretched exponential expression. The conventional power law of degradation is just the approximation of this general form. Very good agreement has been found between the theoretical model and the experimental data. This approach gives more physical insight into the understanding of the mechanism for the interface trap generation.
Deuterium Diffusion, Trapping and Stability in Buried Silicon Dioxide Layers
Authors: Boutry-Forveille A. , Nazarov A. , Ballutaud D.
Published: April 2011

The interaction of hydrogen (deuterium used as tracer) with Si-Si02-Si buried oxide layers (BOX) prepared by thermal oxidation or by oxygen implantation (SIMOX) are investigated using Secondary Ion Mass Spectrometry (SIMS) measurements combined with effusion experiments. The sample deuteration is performed at different temperatures between 150 and 300°C using a radiofrequency plasma. In SIMOX samples, the deuterium diffusion profiles analysed by SIMS show deuterium trapping on implantation defects, and deuterium diffusion in the silicon substrate by permeation through the oxide layer for temperatures higher than 250°C. The deuterium is still detected in the buried oxide layers after isothermal annealing at 600°C during 2 hours. The deuterium trapping at the siliconsilicon dioxide interfaces is analysed.
Electrical Properties of Transition Metal Hydrogen Complexes in Silicon
Authors: Weber J.
Published: April 2011

A summary is given on the electrical properties of transition-metal hydrogen complexes in silicon. Contrary to the general understanding, hydrogen leads not only to a passivation of deep defect levels but also creates several new levels in the band gap due to electrically active transition-metal complexes. We present detailed data for Pt-H complexes and summarize briefly our results on the transition metals Ti, Co, Ni, Pd, and Ag. The introduction of hydrogen at room temperature by wet chemical etching, followed by specific annealing steps allows us to study the formation of the different complexes. In particular, depth profiles of the defect concentrations give an estimate of the number of hydrogen atoms involved in the complexes. Transition-metals binding up to four hydrogen atoms are identified.
Hydrogen-induced Changes of The Microscopic Structure of Microcrystalline Silicon
Authors: Kaiser I. , Nickel N. H. , Pilz W. , Fuhs W.
Published: April 2011

Microcrystalline silicon samples were exposed to an electron cyclotron resonance (ECR) hydrogen plasma at various exposure times and substrate temperatures. Before and after each post-hydrogenation treatment the crystalline fraction, Xc, was determined from Raman backscattering spectra. The results reveal that the change of Xc strongly depends on the structural composition of the starting material. Amorphous samples exhibit an increase of Xc while for ltc-Si specimens the Xc decreases. The decrease of Xc is enhanced for specimens with a high initial crystalline fraction. The same plasma treatment of Si-wafers did not lead to amorphisation. We conclude that the presence of lattice strain is required to observe a H-induced decrease of Xc.
H-passivation of Si(100) By Wet Chemical Cleaning: Discovery of Ordering
Authors: Atluri V. , Herbots N.
Published: April 2011

Si(100) is H-passivated via a modified pre-RCA cleaning followed by etching in HF:alcohol, to produce ordered (1 × 1) templates which desorb at low temperature (T ≥ 600°C). Four sets of 12 wafers, each set processed identically, are used to test reproducibility, and are characterized by Ion Beam Analysis (IBA), Tapping Mode Atomic Force Microscope (TMAFM), and Fourier Transform Infrared Spectroscopy (FTIR). The absolute coverage of oxygen and carbon is measured by ion channeling combined with nuclear resonance at 3.05 MeV for oxygen and 4.265 MeV for carbon, improving the signal to noise by a factor 10 for oxygen and by 120 for carbon. It is then possible for the first time to measure ordering of oxygen atoms with respect to the surface by comparing the amount of oxygen from rotating random spectra to the disordered oxygen measured by channeling. Hydrogen is measured via the elastic recoil detection (ERD) of 4He2+ at 2.8 MeV.

Si(100) etched in HF:methanol after a modified preliminary RCA cleaning yields the cleanest surface. The data suggest that Si(100) passivated by HF in alcohol is terminated by an ordered hydroxide layer, which desorbs at lower temperatures than the more refractory Si02.
Effect of Hydrogen on Surface of Niobium
Authors: Gadgil V. J. , Keim E. G.
Published: April 2011

Niobium single crystals are used as substrate material for constructing superconducting quantum interference device or SQUID. The use of niobium is prompted by the fact that it is a low Tc metallic superconductor. In order to fabricate the device the surface of the crystal has to be polished flat. This is achieved by combination of mechanical polishing and electrochemical polishing. It has been reported that during electrochemical polishing hydrogen can enter the material forming Niobium hydrides. These can result in surface roughening of a magnitude greater than the thickness of the films subsequently deposited. This leads to failure of the films. The problem can be solved by annealing the material at 300° C to remove any hydrogen that might be present. However it is phenomenologically interesting to study the effect of electrochemical hydrogen charging on the surface of Niobium.
Power Supply Distribution and Other Wiring Issues For deep-submicron Ic's
Authors: Lynch W. T. , Arledge L. A.
Published: April 2011

An Interconnect Architecture Optimization (IAO) methodology is proposed. The algorithm makes use of fundamental RLCLL2 relations for wiring delays, as well as predictive 3D interconnect density function histograms with y and x axes of wire length and inverse gate delay. The fundamental RLCLL2 relations determine “maximum” wire lengths as a function of wiring size within the wiring hierarchy; the 3D histogram establishes the pre-physical design allocations of wiring nets within the hierarchy. The decision process begins with the set-asides of wiring for power, clock, and vias, and ends with an optimized number of wiring levels and sizes. Some of the major conclusions of the preliminary analyses are: there are no significant problems with wiring at the lowest level as long as the local wire lengths are appropriately scaled; the MOSFET device may not be able to provide enough current to satisfy the capacitive fanout loads within the future allocations of clock period; and the global wires, despite significant improvements in performance, will continue to provide a design and technology challenge for larger chips and higher frequencies.
Thickness Effects in the Reaction of Cobalt with Slicon-Germanium Alloys
Authors: Boyanov B. I. , Goeller P. T. , Sayers D. E. , Nemanich R. J.
Published: April 2011

The thickness dependence of the reaction of cobalt with silicon and epitaxial silicongermanium alloys (SiGe) was studied. Cobalt layers 25 Å and thicker deposited on Si(100) and annealed at 600°C formed CoSi2. When the thickness of the Co film was reduced to 10 Å the Co/Si(100) reaction resulted in a mixture of CoSi and CoSi2 even after annealing for 20 minutes at 800°C. The products of the reaction of Co with (100)-oriented Si1−x Gex after annealing at 800°C depended on the thickness of the Co film and the Ge concentration in the SiGe layer. When the thickness of the Co film was below a critical value, the only phase formed during the Co/SiGe reaction was CoSi. A mixture of CoSi and CoSi2 was observed when the thickness of the Co film exceeded the critical value. The critical thickness for CoSi2 nucleation increased superlinearly with Ge concentration in the range 0≤x≤0.25, and did not depend on the doping of the Si(100) substrate or the strain state of the SiGe film. XRD and EXAFS measurements indicated no measurable incorporation of Ge had occurred in either the CoSi or CoSi2. The amount of CoSi2 formed above the critical thickness increased monotonically with the thickness of the as-deposited Co film. The observed thickness effect was attributed to preferential Co–Si bonding in the reaction zone, and was modeled in terms of the energy cost of Ge segregation, which accompanies the formation of CoSi and CoSi2 during the reaction of Co with SiGe.
Integration of NiSi SALICIDE for Deep Submicron CMOS Technologies
Authors: Lin X. W. , Ibrahim N. , Topete L. , Pramanik D.
Published: April 2011

A NiSi-based self-aligned silicidation (SALICIDE) process has been integrated into a 0.25 Ion CMOS technology. It involves rapid thermal annealing (RTA) of Ni thin films (300, Å thick) on Si substrates in the temperature range ≈400 - 700 °C. It was found that the NiSi sheet resistance (Rs) gradually decreases with decreasing linewidth. Parameters, such as RTA temperature, substrate dopant (As vs BF2) and structure (single crystal vs poly), were found to have little effects on Rs. NiSi forms a smoother interface with single crystalSi than with poly Si, and has a slightly lower resistivity. MOSFETs based on NiSi show comparable device characteristics to those obtained with Ti SALICIDE. Upon thermal annealing, NiSi remains stable at 450 °C for more than 39 hours. The same is true for 500 °C anneals up to 6 hours, except for NiSi narrow lines (<0.5 μm) on n+ poly Si substrates whose Rs is moderately increased after a 6 hr anneal. This work demonstrates that with an appropriate low-thermal budget backend process, NiSi SALICIDE can be a viable process for deep submicron ULSI technologies.
Growth and Characterization of Self-Aligned Erbium Silicide on N-Type, (100) Oriented Silicon
Authors: Das Suhit R. , LeBrun Les , Sproule G. Irwin
Published: April 2011

In view of its low barrier height to n-type Si, ErSi2 has potential applications as an infrared detector, as low-resistance ohmic contacts and as source/drain regions in Schottky barrier MOSFETs. Although there is a substantial body of work on ErSi2 grown on Si(111), there are relatively few published papers on the growth and properties of ErSi2 on Si(100). In order to develop a CMOS-compatible process, we have studied the growth of ErSi2 using a multi-source, UHV magnetron system to sputter-deposit 20 nm Ti/(10–50) nm Er bilayers on chemically cleaned n-Si(100) substrates followed by ex-situ rapid thermal annealing in N2. Highly oriented ErSi2 in the hexagonal phase was formed at an annealing temperature of 400°C with ErSi2 (100) Si(100). The Ti overlayer and the unreacted Er were selectively etched in HF and HNO3, respectively, leaving behind an ErSi2 layer with a smooth surface morphology, a uniform bulk composition and a planar ErSi2/Si interface. Results of electrical sheet resistance and Schottky barrier height measurements on these layers will be reported.
Suppression of the Phase Transition and Agglomeration of TiSi2 by Addition of Zr Element
Authors: Yoon Sanghyun , Jeon Hyeongtag
Published: April 2011

The formation of C49 TiSi2 phase at high temperatures was investigated by adding the Zr contents in Ti-silicide film. Stabilizing the C49 TiSi2 phase which exhibits lower surface and interface energies than those of the C54 TiSi2 phase at high temperatures was expected to suppress the problems of Tisilicide, such as the phase transition and the film agglomeration. The thin films of Ti and Zr were codeposited (40 nm) on Si substrates in the dual e-beam evaporation system equipped with an ion pump and its base pressure of ∼5 × 10−9 torr. The amounts of Zr contents (5 and 10 atomic %) added on Tisilicide were monitored by in-situ quartz crystal monitor. Immediately after the deposition, this film was annealed by ex-situ vacuum furnace at temperatures between 600 °C and 900 °C in 100 °C increments. The identification of the phase and the chemical composition were investigated by XRD and AES, respectively. The surface and interface morphologies were examined using cross-sectional TEM. The phase transition temperature of TiSi2 was raised with increasing Zr contents. The agglomeration of TiSi2 film was also suppressed by adding Zr element and much improved interface morphologies were observed.
New Approaches for Formation of Ultra-Thin PtSi Layers for Infrared Applications
Authors: Donaton Ricardo A. , Jin Sing , Bender Hugo , Zagrebnov Maxim , Baert Kris , Maex Karen , Vantomme Andre , Langouche Guido
Published: April 2011

PtSi is one of the most used silicides in infrared Schottky barrier detectors due to its low Schottky barrier to p-type Si ( Øb ∼ 0.23 eV). Control of the thickness and uniformity of the silicide layer is fundamental for a good infrared detector performance, since the silicide thickness has to be in the range of 3 to 8 nm. Such thin layers are usually made by evaporation of Pt followed by a furnace annealing. We will show different approaches for fabrication of utra-thin PtSi layers. In all of the processes, high-vacuum sputtering is used for Pt deposition and the silicidation is performed in a rapid thermal annealing system. Smooth and uniform Pt Si layers down to 3 nm thick are formed in this way. It will be shown that the controllability of the thickness during sputter deposition is not a critical issue and the deposition process has a large process window. Moreover, when taking an optimal approach, a large process window can also be found for the RTA step. The implementation of these approaches for device fabrication and some electrial results of diodes made with them will also be presented.