bluuebunny/crossref_metadata_2025 huggingface dataset:
Deposition Rate Monitoring using Laser Induced Fluorescence
Authors: Reiley Timothy C. , Marinero Ernesto E. , Notarys Harris
Published: March 2011

Ultra thin films (< 10 nm) prepared using sputtering or other deposition techniques are becoming more technologically important, with promise of increased importance in the future, particularly in certain magnetic structures. For example, giant-magnetoresistive structures may incorporate individual layers having a thickness < 1 nm. Such a small thickness is commonly associated with relatively short deposition times (∼10 s) and may place limits on the reproducibility and accuracy of the conventional techniques for in situ thickness monitoring or integrated rate monitoring. Experiments have been performed to use laser induced fluorescence (LIF) as a rate monitoring technique for ultra thin films. An RF diode sputtering system was combined with a YAG-pumped, frequency-doubled dye laser to monitor the deposition rale of copper over a range of conditions. When coupled with an absolute calibration reference, the LIF signal gave a reproducible, well-behaved output over a range of pressure and temperature. The technique is potentially advantageous for depositions where rapid (∼1 s) measurements are needed. LIF is also projected to be a valuable tool for detecting very low deposition rates, and it offers the potential of sensitive, real time, spatially-resolved detection in time regimes extending to the nanosecond regime.
Bimetallic Precursors for Ferroelectric Thin Films; Molecular Control of Stoichiometry
Authors: Vaartstra Brian A.
Published: March 2011

The application of ferroelectric oxides in microelectronic and optical devices is critically dependent upon methods to deposit high quality thin films. A major factor influencing the film quality is non-ideal metal stoichiometries caused by process variables. Materials such as PbTiO3 and POZrO3 are well suited for stoichiometric control via molecular precursors having the required metal ratio, eliminating many process variables. Bimetallic precursors for the deposition of lead titanate and PZT thin films have been designed in order to optimize control over the metal stoichiometry. This is accomplished by the synthesis of volatile metalorganic compounds having a 1:1 ratio of Pb:Ti or Pb:Zr. Synthesis and characterization of these novel compounds are presented, and viability for metalorganic chemical vapor deposition (MOCVD) is discussed, based upon decomposition and volatility studies.
Mass Spectrometric Thermal Evolution of Novel Indium Metalorganic Precursors for MOCVD
Authors: Bruno G. , Capezzuto P. , Cicala G. , Losurdo M. , Rossetto G. , Porchia M. , Zanella P.
Published: March 2011

The thermal behaviour of dialkylindium-dialkylamides R2InNR/2 (R,R'=Me, Et) and dialkylindium-azolides R2lnNR' (NR'=Pyrrole, Pyrazole) has been examined by a mass spectrometric thermal evolution technique, in the temperature range 30–400°C. Data on volatility, identity of gasified molecules, threshold temperature and products of the decomposition processes are reported and discussed.
Selective Growth of Polycrystalline Diamond Thin Films
Authors: Ramesham R.
Published: March 2011

Microwave plasma assisted CVD is employed to grow diamond films using a gas mixture of H2 and CH4on various substrates. Diamond has a tendency not to nucleate growth on mirror-smooth finished substrates irrespective of the substrate type (except single crystal diamond). We have developed various processes to enhance the nucleation density of the diamond substantially by damaging or seeding the surface of the substrates. Several process techniques such as 1. silicon nitride and silicon dioxide process, 2. ultrasonic agitation process, 3. selective seeding of diamond by electroplating of Cu, 4. patterning of diamond films by air-microwave plasma etching, etc., were developed to achieve the patterns of diamond on various substrates. Selective growth of doped diamond and low temperature growth of diamond for microelectronic applications have also been achieved by using the above processes (1 and 2). Details on selective diamond growth processes and the morphology of as-deposited selective diamond by SEM are presented.
Pyrolysis Studies and Deposition of Sb Films Using the Novel Omvpe Source (I-Pr)2 SbH
Authors: Gedridge Robert W. , Lee Kenneth E. , Lowe-Ma Charlotte K.
Published: March 2011

The novel antimony source compound di-isopropylantimony hydride, (i-Pr)2 was synthesized and evaluated for use as a volatile Sb-source compound for low temperature growth of Sb-containing semiconductor materials. (i-Pr)2SbH was pyrolyzed in a horizontal atmospheric pressure organometallic vapor phase epitaxy (OMVPE) reactor using Arand H2 as carrier gases. The gaseous exhaust products were analyzed by a residual gas analyzer. Complete pyrolysis of (i-Pr)2SbH in our OMVPE reactor occursaround 300°C and 350°C in Ar and H2, respectively. A comparison between the pyrolysis temperatures and pyrolysis byproducts with respect to a proposed decomposition mechanism of (i-Pr)2SbH is presented. Sb films were grown on Si(100) andSi(111) as low as 200° C. The Sb films were analyzed by Auger and X-ray diffraction. These polycrystalline Sb films were free of detectable carbon by AES. X-ray diffraction data indicated that these Sb films were highly oriented in the [000L] direction.
High Quality P-Doped μc-Si:H Films as Obtained by low Temperature Lpcvd of Disilane
Authors: Manfredotti C. , Fizzotti F. , Amato G. , Boarino L. , Abbas M.
Published: March 2011

Both B- and P- doped silicon films deposited by Low Pressure Chemical Vapor Deposition (LPCVD) at 300 °C (p-type) and 420 °C (n-type) have been characterized by optical absorption, Photothermal Deflection Spectroscopy (PDS), resistivity, Elastic Recoil Detection Analysis (ERDA), Transmission Electron Microscopy (TEM), Convergent-Beam Electron Diffraction (CBED) and Raman spectroscopy measurements. P-doped films, deposited at large PH3 flux rates, show a high degree of microcrystallinity, indicating that P activates the nucleation process even at low temperatures. In this case, values of activation energy of resistivity as low as 0.007 eV were obtained. Both TEM and RAMAN results confirm a volume percentage of micro crystallinity above 30%. On the contrary, B-doped samples are not microcrystalline at least in the doping range investigated, and show a behaviour not different from samples deposited by PECVD.
Si2p Core Level Absorption and Photoemission Spectra of Porous Si
Authors: Nakashima Hisao , Inoue Koichi , Maehashi Kenzo
Published: March 2011

Si2p core level absorption and photoemission spectra are taken for different porous Si layers using synchrotron radiation, toknow the electronic structures of porous Si. The core level absorption spectra show the high energy shift of the conduction band which correlates with the photo-luminescence blue shift. The oxidation states of porous Si are clarified from the photoemission spectra.
Visible Luminescence from Porous Silicon and Siloxene: Recent Results
Authors: Fuchs H. D. , Rosenbauer M. , Brandt M. S. , Ernst S. , Finkbeiner S. , Stutzmann M. , Syassen K. , Weber J. , Queisser H. J. , Cardona M.
Published: March 2011

The optical properties of porous Si (p-Si) are compared to those of siloxene and its derivatives in order to gain more insight into the mechanism of the luminescence observed in p-Si. We report new results of photoluminescence (PL), photoluminescence excitation (PLE), time-dependent and pressure-dependent photoluminescence, and optically detected magnetic resonance (ODMR). Important information about the structural, electronic, and microscopic nature of the two classes of materials are deduced from these experiments. Annealed siloxene and p-Si show very similar properties, suggesting that siloxene-related structures, e.g. electrically isolated Si6-rings, might be responsible for the luminescence in p-Si. The Si-planes in as-prepared siloxene, with their green luminescence, are metastable and are readily oxidized into red-luminescent siloxene configurations.
Characterization of Porous Silicon Layers by Reflectance Spectroscopy
Authors: Theiβ W. , Grosse P. , Münder H. , Lüth H. , Herino R. , Ligeon M.
Published: March 2011

The characterization of porous silicon layers by optical reflectance spectroscopy in the infrared, visible and UV is presented. A fit of simulated to measured spectra is used to interprete the experimental results. We stress that the microgeometry of the porous system determines the optical properties to a large extent and must be taken into account in a correct way in order to achieve reliable results.
Intense Visible Luminescence from Thermally-Oxidized Porous Silicon
Authors: Miyazakj S. , Shiba K. , Sakamoto K. , Hirose M.
Published: March 2011

Photoluminescence from porous silicon oxidized at 800 or 900°C in an N2 +O2 gas mixture has been investigated. The ideal passivation of the porous Si surface with thermally grown oxide results in stable, intense visible-light emission. The steady-state and time-resolved luminescence measured as functions of temperature and excitation power have indicated that a possible pathway for the light emission is the radiative recombination through localized states.
Degradation of Porous Si Layers Caused by Thermal Treatment
Authors: Münder H. , Berger M. G. , Frohnhoff S. , Lüth H. , Rossow U. , Frotscher U. , Richter W.
Published: March 2011

Porous Si Alms formed on different p-doped substrates are studied by Raman spectroscopy, photoluminescence, and spectroscopic ellipsometry. Due to a thermal treatment the morphology is changed. A reduction in the number of nanocrystals with diameters below 30Å is found. It is shown that the photoluminescence is caused by the formation of small nanocrystals and that the effect of amorphous Si as a basic mechanism can be ruled out. The strain which must be taken into account for the interpretation of the Raman spectra decreases with increasing heating temperature.
A Unity Quantum Efficiency Photodiode using Porous Silicon Film
Authors: Zheng J. P. , Jiao K. L. , Shen W. P. , Anderson W. A. , Kwok H. S.
Published: March 2011

A highly sensitive photodiode was fabricated with a metal-porous silicon junction. The spectral response was measured for the wavelength range from 400 nm to 1.075 μm. It was demonstrated that close to unity quantum efficiency could be obtained in the wavelength range of 630 to 900 nm without any anti-reflective coating. The detector response time is about 2 ns for a 9 volts reverse bias. The acceptance angle of photodiode is 2 times better than that of conventional Si detectors. The uniformity and stability were also studied. Possible mechanisms are discussed.
The Depth Dependence of Photoluminescence and Electrolytic Electroluminescence in Porous Silicon Films
Authors: Beale M. I. J. , Cox T. I. , Canham L. T. , Brumhead D.
Published: March 2011

The depth dependence of the photoluminescence (PL) spectrum, both in terms of intensity and wavelength of the peak, is correlated with the electrochemical and chemical processes occurring during the formation of the porous silicon. The depth dependence of the intensity of the electroluminescence (EL) under both anodic bias and cathodic bias, in solutions containing 1M H2SO4 and 0.1M Na2S2O8, is found to be identical with that of the PL. These observations strongly suggest that the silicon skeleton is highly conductive during electrolytic EL, in marked contrast to its high resistivity in air. Strong evidence is provided linking the electrolytic EL to the PL. We extend the quantum confinement based model for PL to the case of electrolytic EL.
Crystallinity and Optoelectronic Properties of μc-SiC:H
Authors: Demichelis F. , Crovini G. , Osenga c. , Pirri C. F. , Tresso E. , Boarino L.
Published: March 2011

Samples of μc-Si1-xCx:H with different degree of crystallinity and different carbon content were deposited by Plasma Enhanced Chemical Vapor Deposition and characterized by means of optical, electrical and structural measurements. The correlation between the degree of crystallinity and the mechanism of conductivity and optical transitions in both amorphous and crystalline phases and at the crystalline-amorphous interfaces is reported and discussed in terms of a band structure model.
Nanocrystalline Ge Synthesis by Reduction of Si1-xGexO2 Formed by High Pressure Oxidation
Authors: Paine David C. , Caragianis Christine , Kim Tae Young , Shigesato Yuzo
Published: March 2011

Nanocrystalline Ge suitable for photoluminescence studies was synthesized from hydrothermally oxidized alloys of Si60Ge40 using steam at 25 MPa and 475°C. Annealing in either an inert atmosphere (UHP N2) or in flowing forming gas (80:20 N2:H2) results in Ge precipitation. In the first case the Ge precipitates are large and concentrated in the bottom portion of the oxide and result from Si reduction of GeO2. In the case of flowing forming gas the Ge precipitates are distributed diroughout die oxide and are formed by reaction between H2 and GeO2. The precipitated samples were analyzed using Raman spectroscopy and cross sectional TEM. Preliminary photoluminescence data reveal that oxide samples excited by the 325 nm line of a HeCd laser after annealing in H2 at both 750 and 800°C for 30 min show strong visible luminescence while unannealed samples do not.
Separation of Nucleation and Growth Processes of Nanocrystalline Silicon by Hydrogen Radical Treatment of Hydrogenated Amorphous Silicon
Authors: Otobe Masanori , Oda Shunri
Published: March 2011

We have investigated nucleation and growth mechanism of nanocrystalline silicon (nc-Si) based on the experimental observation of plan-view transmission electron microscopy. Nanocrystalline Si has been prepared by hydrogen radical annealing of hydrogenated amorphous silicon (a-Si:H) layer, which is deposited on hydrogen radical treated a-Si:H buffer layer. Nanocrystallization depends critically upon hydrogen radical annealing time and the thickness ofa-Si:H layer. Hydrogen radicals play important roles in both nucleation and growth processes in a different way. Growth of nc-Si can be explained by “hydrogen diffusion model”, in which hydrogen radicals diffusing through a-Si:H layer to interface cause nanocrystallization. Our results imply that nuclei for nc-Si are generated at the interface between a-Si:H and under layer when treated by hydrogen radicals.
The Micro-Structure and Electron Conduction Mechanism of Hydrogenated Nano-Crystalline Silicon Films
Authors: He Yuliang , Chu Yiming , Lin Hongyi , Qin Guoguang
Published: March 2011

The hydrogenated nano-crystalline silicon (nc-Si:H) films have been deposited with PECVD method.1–2 The micro-structure of these films has been studied by TEM and HREM. The PECVD nc-Si:H films show fiber texture structure which is exceptional compared with the nano-size materials made by the method of compressing granules method. The fractal dimention of this texture structure has been calculated with a Fourier filtered image. The relationshisps between conductivity and temperature and micro-structure has also been studied and the mechanism of electron conduction is discussed.
Electrical Properties of Boron-Doped μc-Si:H Prepared by Reactive Magnetron Sputtering from c-Si Targets
Authors: Turner W. A. , Williams M. J. , Chen Y. L. , Maher D. M. , Lucovsky G.
Published: March 2011

We discuss the preparation and electrical properties of B-doped μc-Si:H thin films prepared by reactive magnetron sputtering in a hydrogen containing ambient. The B-concentration, and hence the dark conductivity, have been varied by controlling the rf power supplied to two sputtering targets, one, of undoped c-Si, and the other of B-doped c-Si. Films deposited from either target alone display dark conductivity activation energies of approximately 0.5 eV due to Fermi level pinning by native donorlike defects and B-doping for samples prepared from the undoped and B-doped targets, respectively. Films deposited by simultaneously sputtering undoped and B-doped targets display activation energies which first increase to approximately 0.7 eV and then decrease as the fraction of power supplied to the B-doped target is increased. For the combination of deposition parameters used, the cross over point between B-compensated, n-type films, and B-doped p-type films occurs for powers of 50 W supplied to the B-doped target and 100 W to the undoped target. B-compensated samples display trends in photoconductive properties essentially identical to results for μc-Si:H samples prepared by remote plasma CVD. However, IR studies indicate that the material shows significant post-deposition oxide formation. TEM studies confirm the existence of a low-density, porous network. Work is underway to optimize the structural aspects of this material.
Silicon Quantum Wires Oxidation and Transport Studies
Authors: Liu H. I. , Biegelsen D. K. , Johnson N. M. , Ponce F. A. , Maluf N. I. , Pease R. F. W.
Published: March 2011

Fabricating well controlled nanostructures and obtaining precise structural, electrical, and optical information from them are essential for understanding die intrinsic properties of silicon (Si) nanostructures, which in turn is important for exploring the potential of quantum confinement induced light emission from crystalline Si. A combination of high resolution electron beam lithography, anisotropic reactive ion etching (RIE), and thermal oxidation has been successfully applied to obtain sub-5 nm Si columnar structures [1]. A transmission electron microscopy (TEM) technique has also been used to characterize die precise structural dimensions of these columns [1]. To obtain the electrical and optical information, a process based on polyimide planarization was developed to establish electrical contacts to these nanostructures. The same process is also applicable for fabricating device structures to study electrically pumped optical response. Preliminary transport studies have confirmed current conduction through die Si nano-pillars and yielded an estimate of die conductivity.
Electroluminescence as a Function of Electric Field and Temperature in Amorphous Silicon-Carbon Based p-i-n Structures
Authors: Pevtsov A. B. , Pilatov A. G. , Feoktistov N. A. , Zherzdev A. V. , Karabanov S. M. , Muschik T. , Zrenner D. , Schwarz R.
Published: March 2011

Electroluminescence at room temperature with a peak energy between 1.6 and 1.8 eV is observed in a-SiC:H p-i-n devices containing thin injection layers of high bandgap a-SiC:H. The temperature dependence of electroluminescence between 80 K and 320 K is much weaker than expected from the photoluminescence signal. No shift of the electroluminescence spectrum is observed up to voltages of 20 V applied across a 110 nm thick device. The results are compared to well-known features of electroluminescence in a-Si:H devices.
Effects of Diluted-Hydrogen and Hydrogen-Atom-Treatment on the Silicon-Hydrogen Bonding Configurations of Hydrogenated Silicon Films
Authors: Hsu K. C. , Chang H. , Hwang H. L.
Published: March 2011

The silicon—hydrogen bonding configuration studies of hydrogenated silicon films that were fabricated by diluted—hydrogen and hydrogen—atom—treatment methods are presented. The diluted—hydrogen samples tend to show a very sharp line—shape in the NMR spectra as the H2/SiH4 dilution ratio is increased and/or temperature is elevated. The addition of atomic hydrogen treatment can produce the same NMR spectra at a temperature lower than 200°C. The Raman scattering spectra show that the μc—Si phase can be formed by the atomic hydrogen treatment. The infrared absorption spectra also indicate an increase of SiH2 bonding configuration and a hydrogen content reduction when atomic hydrogen treatment is employed. These results suggest that the degree of crystallinity of hydrogenated silicon films can be systematically adjusted.
Micro-Crystalline Silicon in Image Sensor
Authors: Park B. W. , Choi J. I. , Hur C. W. , Oh T. K. , Kang I. K.
Published: March 2011

Amorphous semiconductors play a major role in the field of electronic imaging. The function of an image sensor is to generate an electrical signal corresponding to the light distribution in the optical image. The photodiodes convert light into electrical signal. We investigated the linear image sensor driven by thin film transistor as an switching element, with each photodiode connected to the corresponding thin film transistor. The photo/dark conductivity of photodiode are compared in the case of amorphous silicon and microcrystalline. The influences in contact resistance between microcrystalline n+ layer and the source/drain metal electrode, electron mobility, threshold voltage, and on-off current ratio of thin film transistor with intrinsic microcrystalline silicon channel layer were also investigated.
Growth of Polycrystalline Silicon films at low Temperature by Remote Plasma CVD
Authors: Chul Kim Sung , Chang Park Kyu , Ki Kim Sung , Mok Jun Jung , Jang Jin
Published: March 2011

We studied the growth of polycrystalline silicon by using remote plasma chemical vapour deposition technique. The effects of RF power and the substrate temperature on the structural properties have been investigated. With increasing the RF power, the crystalline volume fraction and the grain size increase up to 100W, but decrease for the further increase in power level. We obtained the poly-Si with the crystalline volume fraction of about 74 at.% at the substrate temperature of 330°C.
Early Stage in Polycrystalline Growth of Si by Fluoro-Oxidation of Silane
Authors: Endo Kenji , Bunyo Masahiro , Shimizu Isamu , Hanna Jun-Ichi
Published: March 2011

We have studied the polycrystalline growth of Si prepared by a reactive gas flow of SiH4 and F2. In a very early stage of the film growth on the amorphous substrates, a thin layer of the amorphous phase was deposited even in the favorable condition for the crystal growth, whose thickness was determined by the growth condition and reached to 200–300nm in a certain condition. The crystalline phase consisted of closely packed small grains perpendicular to the substrate, 200–500nm in diameter, each of which displayed a tooth-like shape with fine structures, indicating a formation of the crystal nuclei in the amorphous phase and their growth to the grains. The generation probability of the nuclei was not uniform in the amorphous phase, high at the region far from the substrate, and very sensitive to the growth temperature, judging from cross sectional TEM micrographs of the films. These suggest that the network propagation of Si in which fluorine, participates the chemical process in the vicinity of the growing surface enhances a formation of the long range ordering in the network, resulting in the generation of the crystal nuclei.
Deposition of Polycrystalline Silicon thin Films by Plasma Enhanced CVD
Authors: Hollingsworth Russell E. , Bhat Pawan K.
Published: March 2011

Polycrystalline silicon films have been grown using high frequency (110 MHz) rf plasma enhanced chemical vapor deposition with a hydrogen diluted silane gas. Polycrystalline growth was obtained when the silane fraction was less than 10% of the total gas mixture for all rf powers, in marked contrast to growth at 13.56 MHz where high power and more dilution are typically required for microcrystalline growth. Grains with [111] and [220] orientations were observed to have grain sizes up to 900 Angstroms. Room temperature free carrier concentrations as low as 5 × 1015 cm-3 for undoped films were determined by capacitance voltage measurements. Boron doped microcrystalline films were grown with conductivity as high as 8 (Ωcm) V
A New Annealing Method to Obtain High Quality Poly-Si
Authors: Song Yoon-Ho , Baek Jong-Tae , Nam Kee-Soo , Kang Sang-Won
Published: March 2011

A new annealing method, a combination of rapid thermal annealing (RTA) and furnace annealing, has been developed to obtain a high quality poly-Si from a-Si deposited by LPCVD. This method produces a large grain poly-Si with good uniformity, which may result from the growth of relatively defect-free nucleus generated at a high temperature by RTA. Poly-Si thin film transistors fabricated by this new annealing method have higher field effect mobility and better uniformity compared with those by the conventional furnace annealing.
Heterogeneous Reactions of GaAs Quantum Dots with Organometallic Precursors
Authors: Saunders Winston A. , Lee Robert B. , Atwater Harry A. , Vahala Kerry J. , Flagan Richard C. , Sercel Peter C.
Published: March 2011

We report recent results on the homogeneous nucleation of GaAs quantum dots from organometallic precursors and subsequent heterogeneous nucleation of epitaxial regrowth of GaAs on the clusters. We find that clusters onto which we have regrown GaAs exhibit a much higher degree of faceting, whereas particles subject to che same thermal cycles but onto which no new GaAs has been grown, though crystalline, have highly irregular shapes. These results suggest that epitaxial regrowth exhibits selectivity in the growth rates on the various crystal facets akin to that found in bulk samples.
Growth of GaAs Epitaxial Microcrystals on a S-Terminated GaAs (001) by Vls Mechanism in MBE
Authors: Koguchi Nobuyuki , Ishige Keiko , Takahashi Satoshi
Published: March 2011

Numerous GaAs epitaxial microcrystals having nearly equal size were fabricated on a S-terminated GaAs(001) surface by a sequential supply of Ga and As molecular beams. The GaAs(001) surface was terminated by sulfur atom in the MBE chamber. The growth of GaAs epitaxial microcrystals is caused by a Vapour-Liquid-Solid(VLS) mechanism. GaAs epitaxial microcrystals were also fabricated on a S-terminated GaAlAs(001) surface by the same procedure.
Composite Semiconductor Nanoparticles
Authors: Zhou H. S. , Honma I. , Komiyama H. , Haus J. W.
Published: March 2011

Nanometer size semiconductor particles coated with another semiconductor can exhibit unusual and interesting phenomena associated with the redistribution of the electron and hole wavefunctions. Using the band offsets and effective-masses, the band gap as well as the wavefunctions can be altered by changing the core radius of the particles. CdS/PbS coated semiconductor nanoparticles are synthesized by ion displacing method and experimental results are discussed along with the theoretical calculation. Optical absorption as well as TEM, Electron diffraction results provides for the evidence that the particles are coated.
TEM Investigation of Si/βFeSi2/Si (100) and (111) Heterostructures Formed by Fe Implantation
Authors: Bulle-Lieuwma C. W. T. , Oostra D. J. , Vandenhoudt D. E. W.
Published: March 2011

Si/βFeSi2/Si (100) and (111) structures were obtained by implantation of 450 keV Fe+ ions with a dose of 6×1017 Fe+ ions/ cm2 into Si substrates. A continuous buried βFeSi2 layer with thickness of 250 nm was formed during subsequent annealing. By transmission electron microscopy it has been found that for (100) Si the layer consists of βFeSi2 grains with lateral dimensions of approximately O.5 μm and for (111) Si of grains of 5 μm in size. The βFeSi2 films exhibit a high degree of epitaxy with the Si substrate. A detailed structural examination shows the occurrence of several epitaxial relationships of βFeSi2 with the Si substrate. In contrast to two-dimensional surface growth techniques, the formation of a buried layer by implantation occurs by a three-dimensional growth process by the coalescence of βFeSi2 precipitates. The different orientations of the βFeSi2 grains in the buried layer are already established by the orientation of the precipitates formed during implantation.
Raman Scattering Study of Boron Doped Diamond Synthesized at High Pressure
Authors: Shiomi Hiromu , Kirillov Dimitry , Hagstrom Stig B.
Published: March 2011

Boron doped diamond synthesized at high pressure was studied using Raman scattering. Shift and broadening of the diamond phonon line was observed and attributed to disorder produced by boron doping. Electronic transitions within boron acceptor states and Fano-type interference between phonons and the electronic continuum have also been observed in the spectra.
Silicon Nitride Deposited at Very Low Silane Pressures Using Electron Cyclotron Resonance Plasmas
Authors: Flemish J. R. , Pfeffer R. , Buchwald W. , Jones K. A.
Published: March 2011

We report on the material properties of SiNx:H films deposited using a 2% SiH4/N2 mixture with additional N2 in an ECR reactor. Deposition rates, refractive index, and stoichiometry have been characterized using ellipsometry, Rutherford backscattering spectroscopy, and infrared spectroscopy. Reactor conditions of 2m Torr total pressure, 650W microwave power, and substrate temperature of 250°C result in high quality, stoichiometric silicon nitride. With a SiH4/N2 ratio = 0.003, hydrogen incorporation is approximately 1.5% and the refractive index is nr =2.0. Lower microwave power and a higher SiH4/N2 ratio result in slightly N-rich films which is attributable to increased H-incorporation. Higher total pressure results in significantly enhanced deposition rates, but with greatly increased H and O content.
Effect of Silicon Surface Treatments on Thin Silicon Nitride Growth
Authors: Nakamura Makoto , Kikuchi Yoshio , Kuwamura Masahiro , Yoshida Masamichi
Published: March 2011

Ultra thin silicon nitride films have been indispensable in high density memory devices as a dielectric. We investigated the effect of the silicon surface state on initial silicon nitride growth process, we have used X-ray Photoelectron spectrometry (XPS), Secondary ion mass spectrometry(SIMS), and Capacitance-Voltage(C-V) characteristics. The results of our study show that the fluorine on silicon surface influences initial silicon nitride growth. The presence of fluorine delays low pressure chemical vapor deposition(LPCVD) silicon nitride growth as well as restraining native oxide growth at the silicon nitride/silicon substrate interface. We propose that it is a key process of thin dielectric films deposition to control fluorine on silicon surface.
Digital Chemical Vapor Deposition of Silicon Oxide/Nitride and its Surface Reaction Study
Authors: Sakaue H. , Nakasako T. , Nakaune K. , Kusuki T. , Miki A. , Horiike Y.
Published: March 2011

In order to fill high quality insulators into narrower spaces in advanced metallizationthe digital CVD (Chemical Vapor Deposition) of multilayer stacked Si oxide and nitride films was studied. Reaction of TES (triethylsilane) with hydrogen (H) atoms was also found to lead to conformal CVD of Si film involving organic species. This reaction took place only on the surface reaction. In-situ FTIR studies reveal that H atoms react with Si-C2H5 bonds in TES and thus generate strong Si-CH3 bonds and weak Si-H bonds, thereby liberating H2 and forming the organic Si film on the surface, and the surface reaction is dominated by the thermal effect from the substrate. Then Si oxide or nitride films were formed by the digitaCVD which repeated a cycle of deposition of this film with subsequent oxidation or nitridation. Oxide film integrity was improved greatly by removing included organic bonds in the TES/H reaction film by exposing the film to H atoms before the oxidation step. Thus electrically excellent multilayer stacked oxide and nitride films were obtained in a deep trench.
Influence of Ion Energy in Plasma Deposition of a-Sio2 Films
Authors: Vallier L. , Joubert O. , Burke R. , Ferrieu F. , Devine R. A. B.
Published: March 2011

Silicon dioxide films have been deposited using a microwave plasma of (SiH4 + O2) excited by distributed electron cyclotron resonance. The ratio of flow rates of the reactive gas was (O2: SiH4) = 7 and no intentional substrate heating was used. The effect of ion energy during deposition, in the 10 — 150 eV range, has been studied through refractive index, infrared absorption bands, chemical etch rate and electrical measurements. It is found that for an ion energy > 50 eV, many of the film characteristics are close to those of thermal SiO2.
Transient Flat-Band Voltage Shifts Following High Voltage Stressing of Thin Oxides
Authors: Wong D. P. , Dumin D. J.
Published: March 2011

It has been shown that the transient decay of the current after removal of a high voltage stressing pulse changed from an exponential RC time constant decay to a very long decay that had a 1/t time dependence[l]. During these long transients the flat-band voltages of the capacitors changed as the traps inside the oxides discharged. The discharge of both positive and negative changes near the silicon-oxide interface have been measured using QSCV measurements. In this paper the transient shifts in the flat-band voltages due to the discharging of stress generated traps in the oxide will be described.
Pump-Probe Charge Integrating Investigation of Trap Emission Kinetics in Ultrathin Mos Capacitors
Authors: Poler J. C. , Irene E. A.
Published: March 2011

As design rules shrink to conform with ULSI device dimensions, gate dielectrics for MOSFET structures are required to be scaled to even thinner proportions. Upon scaling the gate oxides below ∼60Å the interfacial region becomes a significant proportion of the total film. Thus interface properties are weighted more heavily in determining device performance and reliability.

We have developed a Pump-Probe charge integrating measurement technique for studying the emission kinetics of traps in the M/SiO2/Si system. Essentially, a MOS capacitor is pumped by exposure to a charging pulse. The emission of the charge at short time scales (<10ms), can be measured using a delayed application of a probe pulse which determines the remainder of the filled traps as a function of delay time. For a lightly doped p-Si (lll) substrate, we observe an uncommon behavior of the emission kinetics in the initial time regime (< 100ms). A possible explanation for this phenomenon is the perturbation of the emission cross-section of the probed traps due to the presence of another state in communication with the trap site.
Defects Induced by Electron Bombardment and Substrate Doping in SiO2 Thin Films
Authors: Xiong-Skiba P. , Carroll D. L. , Doering D. L. , Siek K. H.
Published: March 2011

Thin SiO2 films grown on silicon substrates were exposed to electron beam irradiation at energies from 100 eV to 2.5 KeV. Then, thermally stimulated exoelectron emission (TSEE) spectra were taken by heating the sample linearly to a maximum temperature of 600°C. We have compared the emission behavior from oxides grown on both n-typeand p-type, (100) and (111) silicon wafers. The TSEE spectra show emission peaks whichcan be categorized by their behavior into two groups. The β emission peaks are characteristic of emission from localized electron traps while the γ emission peaks result from the annealing of beam-induced defects. We have observed changes in the β peaks which appear to be associated with the concentration of dopants in the substrate material. In addition, we have identified a beam energy threshold near the oxygen Is binding energy for the creation of defects. This suggests that defect creation results froman electronic transition similar to electron stimulated desorption.
Thermal Annealing of Radiation-Induced Trapped Charge in Simox and Thermal Oxide Thin Films
Authors: Herve D. , Paillet Ph. , Leray J. L.
Published: March 2011

The results of charge trapping and thermal annealing in X-ray irradiated SiO2 are presented. A comparative study is made between thermal oxide and SIMOX buried oxide behavior. At low dose (10 krad(SiO2)), X-ray induced charge trapping is found to be very different in thermal and SIMOX oxides. Results are interpreted in terms of a relatively large bulk trapping in SIMOX whereas thermal oxide behavior is dominatedby interface trapping. However, at high dose, both oxides behave similarly and are dominated by interface trapping. Etch-back experiments performed on SIMOX irradiated at 10krad (SiO2) and 1 Mrad (SiO2) reveal these two trapping regimes. Isochronal annealings have been performed up to 300°C on irradiated samples. Recovery data are interpreted assuming an energy distribution of trapped charge densities. Detrapping energies located at about 1.05 eV and 1.35 eV have been obtained in SIMOX whereas the thermal oxide exhibits a unique peak at 1.35 eV. Based on these data, SIMOX and thermal oxides are demonstrated to differ significantly.
Evidence for Low Temperature UV Annealing of UVCVD, PECVD and Sog Based SiO2 Films
Authors: Debauche C. , Devine R. A. B. , Licoppe C. , Flicstein J. , Huet F.
Published: March 2011

Ultraviolet radiation has been used to anneal out extrinsic defects in several types of deposited a-SiO2 films. The UV light was obtained from a new krypton UV-VIS-IR lamp with a spectral range of 170 nm <λ<3μ This “cold” annealing was performed on a-SiO2 films, with various thicknesses up to 400 nm. The films were deposited by various techniques, ultraviolet induced chemical vapour deposition (UVCVD), plasma enhanced vapour deposition (PECVD) and spin-on-glass (SOG). Fourier Transform Infra-Red spectroscopy (FTIR) and Electron Spin Resonance (ESR) were used to characterize the effect of the radiation. In the case of UVCVD and SOG a-SiO2 films, it is shown that the UV radiation removes the Si-H bonds and reduces significantly the amount of C-H and C-H3 groups. In both these films, an important reduction in the amount of adsorbed water and Si-OH groups is observed, together with an increase in the number of Si-O bonds. In PECVD films made with tetraethylorthosilicate (TEOS) vapour and O2 as precursor gases, we find evidence for an important reduction in the amount of C and the number of Cn Hy related defects. The UV treatment is effective even at temperatures as low as 100 °C, which suggests that it could constitute a much needed low temperature annealing step.
Silicon and Nitrogen Dangling Bonds Point Defects in PECVD Silicon Oxynitrides Thin Layers
Authors: Viscaino S. , Cros Y. , Ruf B.
Published: March 2011

New defects were revealed in PECVD SiOxNyHz thin layers upon VUV-illuminations with a deuterium (De) lamp. The ESR signal measured after a 8-hour illumination reached a saturated amplitude one or two decades higher than the dark ESR signal. The dark ESR signal level was recovered after a 3-hour anneal at 380°C. In addition to the silicon dangling bonds already identified in the dark ESR, the bridging nitrogen dangling bonds and over-coordinated nitrogen were identified after VUV-radiations. The relative densities of the various kinds of defect are given as a function of the O/O+N oxynitride composition.
Silicon-Nitride for Amorphous Silicon Thin-Film Transistors
Authors: Nickel N. H. , Fuhs W. , Mell H. , Beyer W.
Published: March 2011

Nitrogen-rich amorphous silicon-nitride films a-Si1−xNx:H were prepared by glow-discharge decomposition of gas mixtures of ammonia and silane. With increasing nitrogen content the spin density, Ns, decreases from 4×1018cm−3 (x = 0.55) to 3×1017cm−3 (x = 0.67). These films were used as a gate dielectric in amorphous silicon TFTs. The TFTs are characterized by measurements of the transfer characteristics and by a transient current spectroscopy (TCS). Nitrogen-rich dielectrics with Ns<1018cm−3 have little influence on the transfer characteristic, however, they tend to have a lower sensitivity to bias stress. Using a device-quality nitride (x = 0.64) the properties of the TFTs were varied in two ways: 1) doping of the a-Si:H film with phosphine or diborane and 2) exposure of the nitride film to an oxygen plasma. The variation of the areal density of defect states, Nd, with Ec-EF suggests that the effective density of interface states, Ni, and the characteristic of undoped TFTs are determined by interface defects of the a-Si:H film. The plasma treatment introduces oxygen into a thin superficial layer of the nitride. By varying the exposure time te it is possible to change the properties of the TFTs continuously from nitride like to oxide like.
Performance of Polycrystalline Silicon Thin Film Transistors with Double Layer Gate Dielectric
Authors: Kung Ji-Ho , Hatalis Miltiadis K. , Kanicki Jerzy
Published: March 2011

The electrical characteristics of n- and p-channel poly-Si thin film transistors having a double layer gate dielectric structure are reported. The gate dielectric consists of a silicon dioxide layer and a nitrogen-rich silicon nitride layer, both deposited by PECVD at low temperatures (≥400° C). When the silicon nitride was in contact with the poly-Si film, the effective carrier mobility (μeff), threshold voltage (Vth and subthreshold swing (St) for n-channel devices were 36 cm2/Vsec, -1.8 V and 1.65 V/decade, respectively, while for p-channel devices were 6 cm2/Vsec, -37 and 2.47 V/decade, respectively. These devices were not stable under negative gate bias stress, due to the injection of holes into the silicon nitride. When silicon dioxide was in contact with the poly-Si film, the μeff, Vth and St for n-channel devices were 26 cm2/Vsec, 3 V and 1.63 V/decade, respectively, while for p-channel devices were 10 cm2/Vsec, -22 V and 1.52 V/decade, respectively. These devices were stable under d.c. bias stress.
Eliipsometric Study of Rapid Thermal Annealed PECVD SiN Films
Authors: Alterovitz Samuel A. , Drotos Mark A. , Young Paul G.
Published: March 2011

A conventional parallel plate plasma enhanced chemical vapor deposition system using SiH4-NH3-N2 at 13.56MHz and 300°C was used to deposit SiN films on silicon substrates. Special care was used to assure an oxide free surface before deposition. The silane flow was varied to obtain stoichiometric Si3 N4 and silicon-rich films. Rapid thermal anneal (RTA) was performed for 30 sec at temperatures in the range 600°C — 900°C. Spectroscopic ellipsometry was used to characterize the films. Data was taken for 44 wavelengths (3200–7500Å range) at three angles of incidence on each sample. The structural and optical properties were obtained using several structural models of the film. The models assumed an effective medium approximation for the following three combinations of film constituents: Si3N4 and voids; Si3N4 and amorphous silicon (a-Si); Si3N4, voids and a-Si. In general, the three constituent model gave the best fits to the experimental data. In all films, we observed a decrease in the film thickness and void fraction as the RTA temperature increased. The a-Si percentage did not change vs. the RTA temperature. The reduction in void fraction for the silicon-rich samples was larger than for the Si3N4 film. The results are comparable to those measured by other methods on regular furnace annealed SiN films, i.e. annealing times of 30 minutes or more.
Sub-Nanometer-Equivalent PZT Thin Films Fabricated by Low-Temperature MOCVD
Authors: Miki Hiroshi , Ohji Yuzuru , Tachi Shinichi
Published: March 2011

Ferroelectric PZT (Pb (Zr,Ti)O3) from 100 nm down to 50 nm thick was deposited on Pt/SiO2/Si substrates using MOCVD (Metal Organic Chemical Vapor Deposition) under reduced pressure at 550°C. Using Pb (DPM)2, Zr (DPM)4, and Ti(i–OC3H7)4 as precursors made it possible to control the composition of CVD films and to produce pure perovskite crystalline structure in the range of thickness less than 100 nm. Electrical measurements of the capacitors revealed that 50-nm PZT films typically had a dielectric constant of 500, resulting in the same capacitance as 0.4-nm SiO2.
Jet Vapor Deposition of Lead Zirconate Titanate (PZT) for Thin Film Pyroelectric Detectors
Authors: Golz John , Di Y. D. , Halpern B. , Schmitt J. J. , Cirino Phil , Bartlett A.
Published: March 2011

Thin films of pyroelectric PZT deposited by Jet Vapor Deposition are considered here for application in IR detector arrays. PZT films of 0.5 μm thickness were deposited on platinum coated insulating substrates and then annealed to increase the perovskite grain size. Capacitor test structures were used to measure the dielectric constant, loss, AC resistivity, and pyroelectric coefficient. We compare the results with known values for bulk PZT and discuss their relevance to detector design and performance.
Localization and Electric-Field Modulated Electron Spin Resonance of a Shallow Donor in Simox
Authors: Vanheusden K. , Stesmans A.
Published: March 2011

Low temperature electron spin resonance (ESR) measurements were carried out on a broad range of separation by implantation of oxygen (SIMOX) substrates. The post-implantation forming anneal (T 1325°C) was observed to induce a donor in the SIMOX structure, more specifically, a shallow effective mass donor in Si of axial symmetry and preferential alignment along [001], likely an oxygen-related heat-treatment donor. Controlled etching back experiments revealed that the donor defects reside in an interfacial Si layer of at least 600$$A thick at both sides of the buried oxide layer reaching a local volume density of about 1018 cm−3. In the flat band situation, the donor was observed to be in a diamagnetic, ESR non-active state. Downward sweeping of the Si energy bands near the buried oxide interfaces, relative to the Fermi level, either by in situ positive ate biasing of large area metal-oxide-silicon capacitors fabricated on the buried oxide or γ7-irradiation induced positive charging of the buried oxide, was observed to alter the ionization state of part of the donors into an ESR-active state.
Sulfurized Passivation of GaAs (100) Surfaces
Authors: Li Z. S. , Hou X. Y. , Cai W. Z. , Wang W. , Zhang M. , Dong G. S. , Jin X. , Wang Xun
Published: March 2011

We have developed a new electrochemical passivation method to obtain a quite stable sulfide layer on GaAs surface. This layer is very thick and contains a mixture of Ga, As, S, O and H compounds. The photoluminescence (PL) spectrum of such anodic sulfurized GaAs surface shows big intensity enhancement as compared with that of as-etched GaAs samples; No visual intensity decay occurs under laser beam illumination, which maintains for more than seven months. The structure and composition of the passivation layers are investigated by the X-ray photoelectron spectroscopy and the mechanism of the layer formation is suggested.
The Effect of UV Light on IR Absorption in Chemically Vapor Deposited a-SiNx:H Films
Authors: Seager C. H. , Kanicki J.
Published: March 2011

We have measured the optical absorption properties of Plasma Enhanced Chemically Vapor Deposited (PECVD) films of hydrogenated amorphous silicon nitride (a-SiNx:H) over the energy range from 0.54 to 2 eV using Photothermal Deflection Spectroscopy (PDS). The near-infrared absorption properties of these films provide a quantitative estimate of the amount of H bonded to Si or N as well as a measure of the the density of electronic gap states due to species like Si dangling bonds. Typical PDS spectra obtained on as-deposited films show a broad absorption tail with a large number of narrow absorption peaks. Using the phase sensitive feature of this spectroscopy we are able to separate nitride-related absorption from that arising from the fused quartz substrates. In addition to the broad, featureless band tail, whose magnitude is quite sensitive to optical excitation with light above ̃3.9 eV, we observe a number of narrow absorption peaks which we identify as overtones of localized vibrational modes. Specifically, we see peaks at 0.82 and 1.20 eV which we identify as the 1st and second harmonics of N-H stretching vibrations, and several other peaks whose origins remain undetermined. Prolonged UV excitation produces no detectable change in these vibrational modes, although large changes are seen in the underlying absorption tail. This reinforces previous suggestions that photoinduced changes in these films do not arise from rearrangement of the bonded hydrogen.
Dangling Bonds in Amorphous Silicon Nitride Alloys: Predictions of the Free Energy Model
Authors: Smith F. W. , Efstathiadis H. , Yin Z.
Published: March 2011

The free energy model (FEM) for bonding in a-SixNyHz alloys has been extended to include the contributions of neutral and charged Si and N defects to the free energy of mixing of the amorphous alloy. The FEM predicts that the dominant defects in N-rich alloys are N2o, N2-, and either S3+ or N2+, in contrast to the results of experimental studies that find the dominant neutral, paramagnetic defect to be Si3o. It is concluded that either the observed Si3o defects are not in thermodynamic equilibrium with the amorphous network or the N2o defects have energy levels which lie much higher in the energy gap than currently believed.