bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermochromic VO2 Films Heteroepitaxially Grown on ZnO Coated Glass by RF Sputtering
Authors: Kato Kazuhiro , Keun Song Pung , Shigesato Yuzo , Odaka Hidehumi
Published: April 2011

Vanadium dioxide (VO2) is one of the most attractive thermochromic materials, which shows large changes in optical and electrical properties at around 68°C, nearly room temperature. This thermochromic behavior has been explained in terms of the Mott-Hubbard transition from a high-temperature rutile structure (metal phase) to a low-temperature monoclinic structure (semiconductor phase). We already reported that rf magnetron sputtering using V2O3 or V2O5 targets enable us to deposit polycrystalline thermochromic VO2 films with high reproducibility by introduction of oxygen gas (O2/(Ar+O2)=1∼1.5%) or hydrogen gas (H2/(Ar+H2)=2.5∼10%), respectively, as reactive gases [see ref.1]. In this study, ZnO polycrystalline films were deposited as a buffer layer between the VO2 film and glass substrate also by rf magnetron sputtering, which have been known to exhibit <001> preferred orientation in the wide range of the deposition conditions. Very thin thermochromic VO2 films with thickness of 50nm were successfully deposited on the ZnO coated glass substrate because of the heteroepitaxial relationship of VO2(010)[100]//ZnO(001)[100],[010],[110].
Ion-beam Assisted Deposition of MgO with in situ RHEED Monitoring to Control Bi-axial Texture
Authors: Groves James R. , Arendt Paul N. , Foltyn Stephen R , Jia Quanxi , DePaula Raymond F. , Dowden Paul C. , Kung Harriet , Holesinger Terry G. , Stan Liliana , Emmert Luke A. , Peterson Eric J.
Published: April 2011

We have studied the growth of magnesium oxide using ion-beam assisted deposition (IBAD) to achieve (100) oriented, bi-axially textured films with low mosaic spread, for film thicknesses of 10 nm on silicon substrates. We have refined the process by using reflected high-energy electron diffraction (RHEED) to monitor the growth of IBAD MgO films and found that the diffracted intensity can be used to determine (and ultimately control) final in-plane texture of the film. Here we present results on our work to develop the use of real-time RHEED monitoring to deposit well-oriented IBAD MgO films. The results have been corroborated with extensive grazing-incidence X-ray diffraction (GID). Results of these analyses have allowed us to deposit films on metallic substrates with in-plane mosaic spread less than 7°.
Internal Stress of ITO, IZO and GZO Films Deposited by RF and DC Magnetron Sputtering
Authors: Sasabayashi T. , Song P. K. , Shigesato Y. , Utsumi K. , Kaijo A. , Mitsui A.
Published: April 2011

Mechanical properties such as internal stress or adhesion of transparent conductive oxide (TCO) films are quite important to guarantee the patterning accuracy and the durability for various kinds of commercial applications. In this study, representative TCO films with the thickness of about 200 nm, such as tin-doped indium oxide (ITO), indium-zinc oxide (IZO), and gallium-doped zinc oxide (GZO) films were deposited on unheated glass substrate by rf and dc magnetron sputtering using corresponding oxide targets under various total gas pressure (Ptot) from 0.3 to 3.0 Pa. The internal stress of these TCO films was measured by cantilever method using 50 µ m thick 50mmx5mm micro-sheet glass substrates in relation to the Ptot during the deposition. The ITO films deposited at Ptot lower than 0.7 Pa were polycrystalline and showed large compressive stress, while the amorphous ITO films deposited at 1.5-3.0 Pa showed a very slight tensile stress. On the contrary, the all the IZO films with various thicknesses (50-750 nm) deposited at Ptot of 0.3-3.0 Pa showed entirely amorphous structure, where the compressive stress of IZO films was lower than that of ITO films. Whereas, all the GZO films deposited under Ptot from 0.3 to 5.0 Pa showed polycrystalline structure with <001> preferred orientation, where the compressive stress showed almost constant for all the films.
Mobility in SnO2:F Thin Polycrystalline Films: Grain Boundary Effect and Scattering in the Grain Bulk
Authors: Gilmore A. S. , Al-Kaoud A. , Kaydanov V. , Ohno T.R.
Published: April 2011

Basic electronic properties relevant to the carrier mobility were studied in tin oxide thin films doped with fluorine, prepared by atmospheric pressure chemical vapor deposition. Electrical resistivity, Hall and Seebeck effects, plasma and collision frequencies were measured (the last two by using multiangle spectral ellipsometry) and analyzed for films with carrier concentrations from 1.8×1020 to 5.6×1020 cm−3. Scanning over the sample area of resistivity (four-point probe method) and Seebeck coefficient (thermoprobe) monitored uniformity of electronic properties in plane. Ellipsometry was used to check uniformity over the film thickness. Films with a thickness above 400 nm demonstrated high spatial uniformity and were used for further studies.

Effective mass was determined from combined Hall and plasma frequency measurements and was found to be independent of carrier concentration, which indicates a parabolic band spectrum. Its value was very close to the literature data. In films with carrier concentration ≥3×1020 cm−3 the Hall mobility was very close to the optical mobility calculated based on collision frequency and effective mass values. This indicates a very small contribution of grain boundaries to the total resistivity of films. Thus the measured mobility is close to the electron mobility in the grain bulk.

The scattering parameter value derived from thermopower measurements along with the temperature independent mobility indicated that electron scattering by impurity ions screened by free carriers is the dominating scattering mechanism. Theoretical estimates of mobility are very close to the highest measured mobility values (≥ 30 cm2/Vs) if the spatial dispersion of the dielectric constant is taken into account. Comparison of differently processed films showed that compensation of donor dopant with uncontrolled acceptor centers significantly impacted mobility.
Materials and Device Design with ZnO-Based Diluted Magnetic Semiconductors
Authors: Sato Kazunori , Katayama-Yoshida Hiroshi
Published: April 2011

We propose a materials design to fabricate the transparent and half-metallic ferromagnets in V-, Cr-, Mn+hole, Fe-, Co-, and Ni-doped ZnO based upon ab initio electronic structure calculation. Mn-doped ZnO is anti-ferromagnetic spin glass state, however, it becomes half-metallic ferromagnets upon hole doping. The ferromagnetic state becomes more stable by electron doping in Fe-, Co- or Ni-doped ZnO. From the point of practical applications, it is feasible to realize the half-metallic ferromagnets with high Curie temperature, because n-type ZnO is easily available. We propose the design of new functional devices, such as spin-FET, photo-induced ferromagnets, and spin-injection devices using negative electron affinity in the wide band gap semiconductors.
Relationships Between Microstructure and Reliability in Pzt Mems
Authors: Olson B.W. , Randall L.M. , Richards C.D. , Richards R.F. , Bahr D.F.
Published: April 2011

Piezoelectric oxide films, such as lead zirconate titanate (PZT), are now being integrated into MEMS applications. Many PZT derived systems are deposited using a sol-gel process, which can be used in a microelectronics processing route using spin coating as the deposition method. An application of interest for PZT films is in power generation, where a flexing membrane is used to transform mechanical to electrical energy. The current study was undertaken to identify the relationships between the processing, microstructure, and mechanical reliability of these films. Films were deposited onto both monolithic and bulk micromachined platinized silicon wafers using standard sol-gel chemistries, with roughness and grain size tracked using electron and scanning probe microscopy. Mechanical properties were evaluated in a dynamic bulge testing apparatus. Grain size variations in the Pt film between 35 and 125 nm are shown to have little effect on grain size of the subsequent PZT film and the adhesion of the PZT to the Pt film. Only the Pt film with 125 nm grains was shown to undergo any significant interfacial fracture. Fatigue tests suggest film lifetime is primarily limited by the number of pre- existing flaws in the film from processing. Reducing the microcrack density has been shown to produce films and devices that fail at strains of 1.4% and have mechanical fatigue lifetimes in excess of 100 million cycles at strains simulating the operating conditions.
Random Telegraph-like Signals in Ultrathin CMR Films
Authors: Lisauskas A. , Khartsev S. I. , Grishin A. M.
Published: April 2011

The aim of the present paper is to study low frequency (10 Hz - 10 kHz) noise in low dimensional colossal magnetoresistors (epitaxial CMR films). Two contributions in electrical fluctuations were observed: thermal noise, which depends on resistance and temperature, and excess part, which is determined by resistance fluctuations and are mostly related to film microstructure. For films, thicker than the critical thickness, excess noise spectra has 1/fα dependence with α = 1 ± 0.2. In films thinner than the critical one there are random telegraph like signals (TLS) with Lorentzian spectra appear on the background of 1/f noise. Noise spectroscopy reveals the relaxation process in 4.2 nm thick film has thermally activated character with an energy gap of 20 meV at temperatures below 156 K and 78 meV at T > 156 K.
Colossal Temperature Coefficient of Resistivity in Epitaxial Colossal Magnetoresistive La0.67Ca0.33MnO3 Films
Authors: Khartsev S.I. , Grishin A.M.
Published: April 2011

Epitaxial La0.67Ca0.33MnO3(LCMO) films have been grown by pulsed laser deposition technique on three single crystal substrates: LaAlO3, SrTiO3, and NdGaO3 having lattice mismatch with LCMO film of + 1.26 %, - 0.9 %, and + 0.18 %. We found the transport colossal magnetoresistive (CMR) properties were improved with the reduction of a film/substrate mismatch. Processing conditions for LCMO film on NdGaO3substrate were optimized as well as post-annealing process was employed to achieve a superior temperature coefficient of resistivity TCR = 35 %K−1 and the magnetoresistance MR = 66 % at 7 kOe. To our knowledge, these are the record CMR parameters achieved so far.
Advances in the Development of Quantum Splitting Phosphors
Authors: Setlur A.A. , Comanzo H.A. , Srivastava A.M. , Beers W.W. , Jia W. , Huang S. , Lu L. , Wang X. , Yen W.M.
Published: April 2011

Quantum splitting phosphors (QSPs) are phosphors that could convert VUV radiation into more than one visible photon. These phosphors have the potential to improve the efficacy of current Hg fluorescent lamps and/or Xe lamps by reducing the Stokes shift energy loss after VUV excitation (λexc=185 nm for Hg lamps or 147 nm and 172 nm for Xe lamps provided the emission color of the phosphor matches the eye sensitivity. The current technology in QSPs and their potential limitations will be discussed in this paper. At GE-CRD, we have discovered and developed QSPs that meet the requirements for use in current Hg based fluorescent lamps. The steady state and time resolved optical properties of one of these phosphors, SrAl12O19:Pr3+,Mg2+, has been measured to estimate the maximum quantum efficiency and onset of concentration quenching in this phosphor. The maximum quantum efficiency for SrAl12O19:Pr3+,Mg2+ has been calculated to be ∼125-135% for 185 nm excitation with an upper bound on the Pr3+ doping level of ∼1%.
Enhancement of Photoluminescence from Organic and Inorganic Surface Passivated ZnS Quantum Dots
Authors: El-Khair Hatim Mohamed , Xu Ling , Li Mingha , Ma Yi , Huang Xinfan , Chen Kunji
Published: April 2011

ZnS quantum dots (QDs) chemically synthesized in PVP stabilizing medium have been coated with Zn(OH)2, SiO2and polystyrene (PS) shells as inorganic and organic passivation agents. to synthesize ZnS/Zn(OH)2, ZnS/SiO2and ZnS/PS QDs. PL properties of inorganically passivated ZnS/Zn(OH)2 and ZnS/SiO2 had reported band edge enhancement of 8-10 times, while organically passivated ZnS/PS QDs exhibit tremendous enhancement of band edge emission as much as 10-15 times,. Therefore inorganic and organic coating can passivate trap states of different energies on the surface of ZnS QDs.
Morphology and Cathodoluminescence of Li-Doped SrTiO3:Pr3+,Ga3+, A Red Phosphor Operating at Low Voltages
Authors: Kim Jin Young , Jeon Duk Young , Kang Seong-Gu , Kang Seung-Youl , Suh Kyung-Soo
Published: April 2011

SrTiO3:Pr,Ga phosphor using Li2CO3 as a flux has been investigated as a red phosphor for the application to fluorescent displays operated at low voltage. In SrTiO3:Pr,Ga system, Pr3+can substitute for Sr2+ because the ionic radius of Pr3+almost coincides with that of Sr2+. Previous work, it was found by XRF analysis of SrTiO3:Pr,Ga single crystal that only a small fraction of Pr ions are incorporated in the SrTiO3 lattice. In the present study, the effect of Li addition into SrTiO3:Pr,Ga on the cathodoluminescence (CL) properties was examined at low acceleration voltage. Especially, thanks to the liquid phase of Li2CO3 during the sintering process, doped Li ions act as a lubricant for the efficient incorporation of Pr ions into SrTiO3:Pr,Ga lattice. Furthermore, it is found that the Li addition could enhance the generation of the characteristic emission of Pr-activated SrTiO3phosphors.
Synthesis and luminescence properties of colloidal lanthanide doped YVO4
Authors: Huignard Arnaud , Gacoin Thierry , Chaput Frédéric , Boilot Jean-Pierre , Aschehoug Patrick , Viana Bruno
Published: April 2011

Aqueous colloidal solutions of well dispersed YVO4:Ln (Ln = Eu, Nd) nanoparticles are synthesized through precipitation reactions at room temperature. In the case of YVO4:Eu, a luminescence quantum yield of 15% is found, which is not as high as in the bulk due to the existence of residual crystalline defects and nonradiative relaxations from the hydroxylated surface. Appropriate hydrothermal annealing and deuteration of the surface allow to rise the yield up to 38%. Incorporation of the nanocrystals into a transparent silica matrix is achieved through preliminary coating of the particles with a functionnalized silicon alkoxide and further dispersion into a sol-gel precursor solution. Such sol-gel materials doped with YVO4:Nd nanocrystals are transparent and exhibit the typical emission at 1.06 μm of the Nd3+ ion.
Nanocrystal Quantum Dots: Building Blocks for Tunable Optical Amplifiers and Lasers
Authors: Hollingsworth Jennifer A. , Mikhailovsky Alexander A. , Malko Anton , Klimov Victor I. , Leatherdale Catherine A. , Eisler Hans –J. , Bawendi Moungi G.
Published: April 2011

We study optical processes relevant to optical amplification and lasing in CdSe nanocrystal quantum dots (NQD). NQDs are freestanding nanoparticles prepared using solution-based organometallic reactions originally developed for the Cd chalcogenides, CdS, CdSe and CdTe [J. Am. Chem. Soc. 115, 8706 (1993)]. We investigate NQDs with diameters ranging from 2 to 8 nm. Due to strong quantum confinement, they exhibit size-dependent spectral tunability over an energy range as wide as several hundred meV. We observe a strong effect of the matrix/solvent on optical gain properties of CdSe NQDs. In most of the commonly used solvents (such as hexane and toluene), gain is suppressed due to strong photoinduced absorption associated with carriers trapped at solvent-related interface states. In contrast, matrix-free close packed NQD films (NQD solids) exhibit large optical gain with a magnitude that is sufficiently high for the optical gain to successfully compete with multiparticle Auger recombination [Science 287, 10117 (2000)]. These films exhibit narrowband stimulated emission at both cryogenic and room temperature, and the emission color is tunable with dot size [Science 290, 314 (2000)]. Moreover, the NQD films can be incorporated into microcavities of different geometries (micro-spheres, wires, tubes) that produce lasing in whispering gallery modes. The facile preparation, chemical flexibility and wide-range spectral tunability due to strong quantum confinement are the key advantages that should motivate research into NQD applications in optical amplifiers and lasers.
Excited State Relaxation Mechanisms in InP colloidal Quantum Dots.
Authors: Rumbles Garry , Selmarten Don , Ellingson Randy E. , Blackburn Jeff , Yu Pingrong , Smith Barton B. , Micic Olga I. , Nozik Arthur J.
Published: April 2011

We report photoluminescence, linear absorption and femto-second transient bleaching spectra for a colloidal solution of indium phosphide (InP) quantum dots at ambient temperatures. The photoluminescence quantum yield is shown to depend not only upon the size of the quantum dots, with larger dots exhibiting higher quantum yields, but also upon the excitation wavelength. At short wavelengths, photoluminescence excitation spectra deviate markedly from the absorption spectra indicating that an efficient non-radiative deactivation pathway becomes prominent at these higher photon energies. We interpret this observation in terms of an inefficient relaxation mechanism between the second excited state and the lowest energy excited state from which the emission emanates. The results are consistent with the existence of a phonon bottleneck.
Chemical mapping of indium rich quantum dots in InGaN/GaN quantum wells
Authors: Sharma N , Cho H K , Lee J Y , Humphreys C J
Published: April 2011

Indium clustering in InGaN/GaN multiple quantum wells (MQWs) is believed to be responsible for the high luminescent efficiency of GaN based light emitting diodes. In this paper we show that substantial clustering can be induced by reducing to zero the interruption time between growth of the GaN barrier layer on the InGaN quantum well. Photoluminescence (PL) shows that this has the effect of increasing the luminescence intensity and decreasing the band gap energy (higher indium concentration). The clusters or quantum dots were examined and quantified by energy filtered transmission electron microscopy (EFTEM), which was used to form chemical distribution maps of indium, gallium and nitrogen. In this paper we will show that this technique can accurately calculate the indium concentration and distribution in the quantum wells. The calculations show that InxGa1−xN quantum dots (width = 1.3nm) exhibit an In concentration of up to x = 0.5, which are embedded in a quantum well matrix with x = 0.05.
Optical and Electrical Properties of Cr-SiO Thin Films for Flat Panel Displays
Authors: Wood Richard , Hofstra Peter , Johnson David
Published: April 2011

Low temperature fabrication of transparent conducting materials is a key issue in flat panel display production. Though Cr-SiO cermet thin films have predominantly been used as thin film resistors in a variety of microelectronics applications, it is shown in this paper that the material can successfully be used as a transparent to semi-transparent conductor in some applications if the value of the extinction coefficient, k, can be kept low (<0.3). Thus, a detailed study of the interdependence of the resistivity and optical properties of Cr-SiO is presented for the first time within the context of its use in the flat panel display industry. Specifically, Cr-SiO can be employed as part of Luxell's optical interference structure, known as the Black Layer™, US patent 5,049,780, used to increase contrast in TFEL and OLED displays.
Conductance Imaging of the Depletion Region of Biased Silicon PN Junction Device
Authors: Park Jeong Young , Phaneuf R. J. , Williams E. D.
Published: April 2011

Simultaneous conductance imaging and constant current mode STM imaging have been used to delineate Si pn junction arrays over a range of reverse bias conditions. Conductance has been obtained by adding a modulation signal to voltages applied in the p and n regions of a model device, and by measuring the modulation signal of the tunneling current with a lock-in amplifier. Both constant current and conductance imaging ofthe electrically different regions (n, p, and depletion zone) show a pronounced dependence on applied pn junction bias. The conductance contrast is mainly due to electrically different behaviors of metal-gap-semiconductor junction which are determined by the tip-induced band bending of the oxide-passivated silicon surface.
Demonstration of the state-of-the-art of formation and characterization of ultra-shallow junctions
Authors: Borden P. , Al-Bayati A. , Madsen J. , Lazik C. , Carey P. , Bechtler L. , Mayur A.
Published: April 2011

Doping process windows are becoming very narrow as VLSI technology nodes scale to smaller and smaller dimensions. The time and cost required to develop new doping methods and the desire to re-use equipment will make it likely that current methods will be applied as long as possible. This means that existing process tools will have very tight stability and uniformity requirements, and metrology will be required to drive process control. The paper describes the state-of-the-art of both doping processes involving ion implantation and spike annealing, and new metrology based on Carrier IlluminationTM methods that will be required to implement in-line process control for these processes. CI offers depth resolution on the order of1Å, providing a level of control required to extend existing doping methods. The prospects of new methods such as Laser Thermal Annealing (LTA) are also discussed.
Use of isotopically pure silicon material to estimate silicon diffusivity in silicon dioxide
Authors: Tsoukalas D. , Tsamis C. , Normand P.
Published: April 2011

In this paper we report measurement of the silicon diffusion coefficient in silicon dioxide films using isotopically enriched 28Si silicon dioxide layers. 30Si atoms are introduced in excess in a stoichiometric isotopically pure silicon dioxide layer either by ion implantation or by a predeposition technique and the time evolution of the 30Si concentration profile under various thermal conditions is monitored using SIMS. The estimated diffusivity values are significantly higher than previouslyreported values for Si diffusion within a stoichiometric oxide and closer to reported values for excess Si diffusion within an oxide.
Vacancy and oxygen behavior in carbon highly doped silicon
Authors: Lavéant Pierre , Werner Peter , Engler Norbert , Goesele Ulrich
Published: April 2011

Carbon doping of silicon has gained interest since in high concentrations, carbon can reduce oreven suppress undesirable diffusion of the base dopant boron in silicon-based bipolar transistors. This behavior can only be understood in taking into account the silicon point defects i.e. vacancies and self-interstitials. In this work, we observe the oversaturation of vacancies produced by a high carbon concentration duringannealing. Experiments with a vacancy diffusing dopant, Antimony, are shown and prove this effect: in a carbon rich sample, the antimony diffusion is enhanced about 8 times compared to samples with a much lower carbonconcentration. We also investigate the carbon co-precipitation with oxygen. The carbon precipitation, asSiC, is facilitated with a high oxygen concentration. We explain this affinity by an exchange of point defects and a volume compensation. Finally, we show the precipitation of oxygen in relation to the vacancy oversaturation at 900°C.
Ab-Initio Modeling of C-B Interactions In Si
Authors: Liu Chun-Li , Windl Wolfgang , Borucki Len , Lu Shifeng , Liu Xiang-Yang
Published: April 2011

We present the results of ab-initio calculations for the structure and energetics of small boron-carbon (BCI) as well as carbon-carbon (C2I) clusters in Si, a continuum model for the nucleation, growth, and dissolution of the clusters, and experimental investigation by SIMS. The modeling results suggest that these clusters may play a role in controlling B diffusion in Si and SiGe systems and the experimental results seem to support the modeling findings.
Effect of the Ge preamorphisation dose on the thermal evolution of End of Range defects
Authors: Colombeau B. , Cristiano F. , Marrot J-C. , Assayag G. Ben , Claverie A.
Published: April 2011

In this paper, we study the effect of the Ge+ preamorphisation dose on the thermal evolution of End of Range (EOR) defects upon annealing. Amorphisations were carried out by implanting Ge+ at 150 keV to doses ranging from 1×1015 ions/cm2 to 8×1015ions/cm2. Rapid Thermal Annealing (RTA) was performed for various time/temperature combinations in nitrogen ambient. Plan view transmission electron microscopy under specific imaging conditions was used to measure the size distributions and densities of the EOR defects. We found that for a fixed thermal budget, the increase in the Ge ion dose results in an increase in the defect density but has no effect on the defect size distribution. This invariance of the mean size of defects with respect to the initial supersaturation introduced in the matrix is an expected characteristic of a conservative Ostwald ripening mechanism. Moreover, the total number (Nb) of Si interstitial atoms bound to the EOR defects is a monotonically increasing function of the Ge ion dose. Furthermore, we found that Nb is directly proportional to the number of Si atoms in excess of the vacancies found below the a/c interface as calculated by MonteCarlo simulations. This is consistent with the “excess interstitial” model which explains the origin of the EOR defects.
Determining the Ratio of the Precipitated versus Substituted Arsenic by XAFS and SIMS in Heavy Dose Arsenic Implants in Silicon
Authors: Sahiner M. A. , Novak S. W. , Woicik J. C. , Liu J. , Krishnamoorty V.
Published: April 2011

Doping silicon with arsenic by ion implantation above the solid solubility level leads to As clusters and/or precipitates in the form of monoclinic SiAs causing electrical deactivation of the dopant. Information on the local structure around the As atom, and the As concentration depth profiles is important for the implantation and annealing process in order to reduce the precipitated As and maximize the electrically activated As. In this study, we determined the local As structure and the precipitated versus substituted As for As implants in CZ (001) Si wafers, with implant energies between 20 keV and 100 keV, and implant doses ranging from 1 × 1015/cm2 to 1 × 1018/cm2. The samples were subjected to different thermal annealing conditions. We used secondary ion mass spectrometry (SIMS) and UT- MARLOWE simulations to determine the region where the As-concentration is above the solid solubility level. By x-ray absorption fine structure spectroscopy (XAFS), we probed the structure of the local environment around As. XAFS being capable of probing the short-range order in crystalline and amorphous materials provides information on the number, distance and chemical identity of the neighbors of the main absorbing atom. Using Fourier analysis, the coordination numbers (N) and the nearest-neighbor distances (R) to As atoms in the first shell were extracted from the XAFS data. When As precipitates as monoclinic SiAs, the nearest-neighbor distances and coordination numbers are ∼2.37 Å and ∼3, as opposed to ∼2.40 Å and ∼4 when As is substitutional. Based on this information, the critical implant dose where the precipitation/clustering of As starts, and the ratio of the substitutional versus cluster/precipitate form As in the samples were determined.
Boron Segregation and Electrical Properties in Polycrystalline SiGeC
Authors: Stewart E. J. , Carroll M. S. , Sturm J.C.
Published: April 2011

Previously, it has been reported that PMOS capacitors with heavily boron-doped polycrystalline SiGeC gates are less susceptible to boron penetration than those with poly Si gates [1]. Boron appears to accumulate in the poly SiGeC layers during anneals, reducing boron outdiffusion from the gate despite high boron levels in the poly SiGeC at the gate/oxide interface. In this abstract, we report clear evidence of strong boron segregation to polycrystalline SiGeC layers from poly Si, with boron concentration in poly SiGeC (Ge=25%, C=1.5%) increasing to four times that of adjacent poly Si layers. A separate experiment confirms that this result is not due to any SIMS artifacts. Electrical measurements of heavily in-situ doped single layer samples show that the conductivity of poly SiGeC is similar to poly Si and remains roughly constant with annealing at 800°C. However, in a two-layer sample where the poly SiGeC is initially lightly doped and subsequently heavily doped by diffusion by from an adjacent poly Si layer, conductivity appears lower than in poly Si.
Atomistic simulations of extrinsic defects evolution and transient enhanced diffusion in silicon
Authors: Claverie A. , Colombeau B. , Cristiano F. , Altibelli A. , Bonafos C.
Published: April 2011

We have implemented an atomistic simulation of the Ostwald ripening of extrinsic defects (clusters, {113}'s and dislocation loops) which occurs during annealing of ion implanted silicon. Our model describes the concomitant time evolution of the defects and of the supersaturation of Si interstitial atoms in the region. It accounts for the capture and emission of these interstitials to and from extrinsic defects (defined by their formation energy) of sizes up to thousands of atoms and includes a loss term due to the interstitial flux to the surface. This model reproduces well the dissolution of {113} defects in Si implanted wafers. We have subsequently studied the characteristics of TED in the case of B implantation at low and ultra low energy. In such cases, the distance between the defect layer and the surface plays a crucial role in determining the TED decay time. The simulations show that defect dissolution occurs earlier and for smaller sizes in the ultra-low energy regime. Under such conditions, TED is mostly characterized by its “pulse” component which takes place at the very beginning of the anneal, probably during the ramping up. In summary, we have shown that the physical modelling of the formation and of the growth of extrinsic defects leads to a correct prediction of the “source term” of Si interstitials and at the origin of TED.
An Evaluation on The Effects of Newly Designed Abrasives in CMP Slurry
Authors: Kawahashi Nobuo , Hattori Masayuki
Published: April 2011

Newly designed abrasives with various particle morphology and component have been prepared and evaluated in terms of polish efficiency for CMP application. Polymer sphere with uniformed particle size and special functional group were prepared by soap-free emulsion polymerization. CMP slurry including polymer abrasives indicated characteristic properties such as dishing, erosion and low defectivity for metal and dielectric surface. This study has been also conducted on the preparation of composite particles consisting of polymer core covered with inorganic composition such as zirconium compound, titanium compound, SiO2 and Al2O3. The controlled hydrolysis and heterocoagulation systems were proposed as preparation methods of composite particles. 1st step Cu-CMP Slurry with composite particles as abrasion indicated an excellent dishing, erosion and their over-polish-margin. Particularly these composite particles were useful to prevent increasing scratch on the TEOS and low-k dielectric materials surface in 2nd step CMP process.
Copper CMP for Dual Damascene Technology: Some Considerations on the Mechanism of Cu Removal
Authors: Wei David , Gotkis Yehiel , Li Hugh , Jew Stephen , Li Joseph , Srivatsan Sri , Simon Joseph , Boyd John M. , Ramanujam KY , Kistler Rodney
Published: April 2011

It was found in a Cu-CMP process using EP-C 5001 slurry and IC 1000 pad that Cu removal rate, being extremely low without H2O2 in the slurry, increases up to a maximum with the addition of H2O2, and then decreases again. Analysis of polarization curves and Eh-pH diagrams shows that without H2O2 Cu has the lowest electric potential, as a result, the highest thermodynamic stability in the Cu/slurry system. Addition of H2O2 shifts the potential up and induces the formation of Cu2O, resulting in a high removal rate. At high H2O2 concentration, a CuO passivation film is formed. In this case, only mechanical removal of the passivating oxide film allows the process to proceed. It is speculated that the moving pad surface adheres the oxidized species via the formation of hydrogen bonds with oxygen atoms of copper oxide molecules, thus detaching them from the wafer surface. Each oxygen atom is capable of pulling out two Cu atoms if Cu2O is formed on the surface and only one Cu atom if CuO is formed. This would explain why the removal rate is high at low H2O2 concentration and low at high H2O2 concentration.
A Study on STI and Damascene CMP using Chip Level Simulation
Authors: Kim Kyung-Hyun , Kim Yoo-Hyon , Kim Kwang-Bok , Hong Chang-Ki , Yoo Moon-Hyun
Published: April 2011

Simulation of chemical-mechanical polishing is important because the chip-level planarity are difficult to control. The simulator has been developed for predicting and optimizing the thickness distribution after the STI and damascene CMP as well as ILD CMP using chip-level pattern density, elastic spring model and erosion model. In this study, the results of CMP simulation is shown to agree well with the measured data. The simulator can be used to optimize CMP process conditions and to generate design rules for filling dummy patterns which are used to improve the planarity and uniformity.
Slurry Retention and Transport during Chemical-Mechanical Polishing of Copper
Authors: Jindal Anurag , Li Ying , Narayanan Satish , Babu S. V.
Published: April 2011

This work investigates the retention and transport of chemical species and abrasive particles during chemical-mechanical polishing (CMP) of copper (Cu). “Slurry step-flow” experiments, in which the concentrations of the chemicals and abrasives in the slurry are altered in steps during polishing were conducted with hydrogen peroxide (H2O2)/glycine based slurries. Two different pads, Suba-500 and IC 1400 (with k grooves), were compared in terms of their slurry retention and transport characteristics. With these experiments, it has been shown that both the abrasives and chemicals are constantly replaced during a typical CMP process. Better polishing performance of the IC 1400 over Suba 500 is a result of improved transport of the chemicals and the abrasives between the wafer/pad interface.
Modeling of Pattern Dependencies for Multi-Level Copper Chemical-Mechanical Polishing Processes
Authors: Tugbawa Tamba , Park Tae , Lee Brian , Boning Duane
Published: April 2011

Wepropose an integratedcontact mechanics and density-step-heightmodel of pattern dependencies for the chemical-mechanical polishing (CMP) of multi-level copper interconnects, and show preliminary comparisons with experimental data for the overburden copper removal stage. The model uses contact mechanics to correctly apportion polishing pressure on all sections of an envelop function that reflects the long-range thickness differences on the chip, or region of interest. With the pressure over the entire envelop known, the density-step-height part of the model is then used to compute the amount of material removed in the local “up-areas” and “down-areas”. ThismodelshowspromiseinaccuratelyandefficientlypredictingpostCMPcopperanddielectric thicknesses across an entire chip.
A Contact-Mechanics Based Model for Dishing and Erosion in Chemical-Mechanical Polishing
Authors: Vlassak Joost J.
Published: April 2011

We present a new model for dishing and erosion during chemical-mechanical planarization. According to this model, dishing and erosion is controlled by the local pressure distribution between features on the wafer and the polishing pad. The model uses a contact mechanics analysis based on the work by Greenwood to evaluate the pressure distribution taking into account the compliance of the pad as well as its roughness. Using the model, the effects of pattern density, line width, applied down-force, selectivity, pad properties, etc. on both dishing and erosion can be readily evaluated. The model may be applied to CMP used for oxide planarization, metal damascene or shallow trench isolation.

The model is implemented as an algorithm that quickly calculates the evolution of the profile of a set of features on the wafer during the polishing process. With proper calibration of the process parameters, it can be used as a tool in optimizing the CMP process and implementing CMP design rules.
A CMP Numerical Model Combining Die Scale and Feature Scale Polishing Characteristics
Authors: Delage Stéphanie , Meyer Frank , Springer Goetz
Published: April 2011

In this paper a new numerical model combining die scale and feature scale polishing characteristics for oxide CMP is proposed. This work is based on the effective density model [1-3] which takes into account a die scale pad deformation. We have extended this model to include the description of material removal at the feature scale. A pseudo topography discretization allows us to describe the polishing in down areas more accurately depending on the down area width. The physical parameters considered include the deformation of the polishing pad (die scale and feature scale), the removal rate of a blanket wafer polished under the same process conditions, and the removal rate in down areas for small polishing times.

Comparison of simulated results with MIT testreticle experiments has been performed and evaluated.
Control of Pattern Specific Corrosion During Aluminum Chemical Mechanical Polishing
Authors: Kim Hyungjun , Kwon Panki , Lee Sukjae , Kim Hyung-Hwan , Lee Sang-Ick , Song Seo-Young , Nam Chul-Woo
Published: April 2011

A pattern specific corrosion of aluminum wires was found during aluminum chemical mechanical polishing process. This paper presents and discusses the particular pattern dependency of the corrosion behavior and effective control methods in order to reduce the corrosion. An aluminum single damascene structure on silicon dioxide thin film was prepared and the effects of process variables and pattern configuration on corrosion behavior were extensively explored. The corrosion behavior was quantitatively analyzed using sheet resistance of corroded line. It was demonstrated that corrosion of aluminum wire was associated with cleaning media and pattern configuration. The area ratio between sub-micron size line and pads was the most important factors to determine the corrosion behavior. A post cleaning chemical including corrosion inhibitor couldn't prevent the corrosion perfectly. It was found that sacrificial dummy lines could reduce the aluminum corrosion, which suggests that the aluminum corrosion could be controlled by the structural consideration in aluminum damascene.
Heteroepitaxial growth of TaN on MgO(001) and TiN(001)/Si(001) by pulsed laser deposition
Authors: Cheung H. Y. , Wong K.H.
Published: April 2011

Epitaxial TaN(001) films have been successfully grown on MgO(001) single crystal and TiN(001) buffered Si(001) substrates by pulsed laser deposition method. Crystalline TaN layers of about 100 nm thick were deposited under a base pressure of 5 × 10−6 Torr and at substrate temperatures ranging from 500°C to 700°C. X-ray diffraction results suggested that stoichiometric TaN films with cube-on-cube <001>TaN∥<001>MgO heteroepitaxy are obtained in this temperature range. Plan-view and cross-sectional electron microscopy analysis revealed excellent structural quality and sharp interface boundary. TaN films grown on TiN(001) buffered Si(001), however, showed a mixture of TaNx (with x ≤ 1) components. Although the (001)-orientated TaN is always present prominently, the nitrogen deficient TaNx components are often co-existed in the films and show up as a broad peak in the X-ray diffraction profile. Stoichiometric and single phase TaN(001) films can only be obtained in a narrow temperature window at around 550oC and heteroepitaxial relation <001>TaN∥<001>TiN∥<001>Si has been demonstrated.
Vacancies in Homoepitaxially-Grown Ag and Cu films
Authors: Botez Cristian E. , Elliott William C. , Miceli Paul F. , Stephens Peter W.
Published: April 2011

X-ray scattering experiments on the homoepitaxial growth of Ag(001) Ag(111) and Cu(001) show that high vacancy concentrations can be achieved during low temperature deposition. It is observed that the vacancies, which can attain concentrations on the order of 2%, extend throughout the thickness of the deposited film. Moreover, vacancies are found to have a profound effect on the evolving morphology of certain surfaces, which is discussed in terms of prior studies of kinetic roughening in these systems.
Dislocation Arrays in the Interfaces between Substrates and Epitaxial Islands
Authors: Lakshmanan Annamalai , Gopal Vidyut , King Alexander H. , Kvam Eric P.
Published: April 2011

We present a model for dislocation array image effects during epilayer island growth. Misfit dislocations often appear at an interface between phases, to accommodate a lattice mismatch. In many situations, such as early film growth, one of the phases may be discontinuous, leaving the interface region clearly bounded. The structure of such a finite interface differs from the normally-modeled infinite boundary because of end effects near the edges of the islands. We have modeled the dislocation structure of such a finite interface in MBE-grown InAs islands on GaP, and compare our results to high-resolution images of the same structure. The 11% misfit causes dislocation introduction from the outset of growth. Islands containing between 4 and 14 dislocations were examined, and dislocation spacings were found to be enlarged near the island perimeters. The model provides a clear understanding of this and other effects.
“Magic” Nanostructures During the Early Stage of Thin Film Growth
Authors: Zhang M. , Efremov M. Yu. , Schiettekatte F. , Olson E. A. , Allen L. H.
Published: April 2011

The behaviors of thin indium films in the early stage of growth are studied in situ by a novel ultra-sensitive thin film scanning calorimetry technique. The films consist of ensembles of self-assembled indium nanostructures whose melting temperatures are strongly influenced by size. We experimentally determine the relationship between a nanostructure's radius and its melting point by combining the measured caloric results with nanostructure size distributions obtained from TEM. The results show a linear melting point depression. Moreover, by looking at the fine structures of these caloric curves, we found the discrete nature of nanostructures during the early stage of thin film growth. The measured heat capacity values show several local maxima at certain temperatures. This suggests that preferred energy states exist among these supported nanostructures on amorphous surfaces. These local maxima are related to each other by increments of one monolayer of indium atoms. These findings could be extended from the magic numbers observed previously in cluster beams studies.
Electron Beam - Directed Vapor Deposition of Multifunctional Structures
Authors: Queheillalt D. T. , Katsumi Y. , Wadley H. N. G.
Published: April 2011

Multifunctional structures are those that combine load bearing support in addition to supplemental functions such as actuation, electrochemical energy storage or thermal management. Electron beam - directed vapor deposition (EB- DVD) technology has been used for the deposition of templated cellular structures for micro heat-pipe structures and porous electrode coatings for rechargeable nickel - metal hydride cells. In addition to load bearing support, the tem- plated cellular structures exhibit enhanced thermal management characteristics and the electrochemical cells can be integrated into the load bearing supports of linear and truss based structures leading to their multifunctionality. Dur- ing EB-DVD, the electron beam evaporated vapor flux is encompassed by a rarefied transonic inert gas jet, entraining the vapor in a non-reactive gas flow and transporting it onto a polymer or metal template structure. Here, EB-DVD technology has been used to synthesize copper based templated cellular structures for thermal management systems and porous nickel coatings for the positive electrode of rechargeable nickel - metal hydride cells.
The Improvement of Thin Polymer Film Properties Through Plasma Immersion Ion Implantation and Deposition Technique
Authors: Rangel Elidiane C. , Cruz Nilson C. , Mota Rogério P. , Algatti Maurício A. , Honda Roberto Y. , Kuranaga Carlos , da Marcos D.
Published: April 2011

Thin polymer films were deposited from acetylene and argon mixtures by plasma immersion ion implantation and deposition. The effect of the pulse frequency, ∨, on molecular structure, optical gap, contact angle and hardness of the films was investigated. It was observed progressive dehydrogenation of the samples and increment in the concentration of unsaturated carbon bonds as the pulse frequency was increased. Film hardness and contact angle increased and optical gap decreased with ∨. These results are interpreted in terms of the chain unsaturation and crosslinking.
Remote Plasma Enhanced Chemical Vapor Deposition of TiOx Films from Titanium Tetraisopropoxide
Authors: Nakamura Masatoshi , Kato Shinichi , Aoki Toru , Hatanaka Yoshinori
Published: April 2011

TiOx thin films were prepared from titanium tetraisopropoxide (Ti-(O-i-C3H7)4, TTIP) in a remote plasma enhanced chemical vapor deposition (RPE-CVD) using a mixture of hydrogen/oxygen plasma gas. Emission spectra suggested that H-radicals dissociated TTIP molecules in gas phase. By mixing with oxygen, H-radical density was increased with the correlation effect to result in enhancement of deposition rate. Deposition rate was also influenced by OH-radicals. OH-radicals caused deactivation of precursors and hence suppressed Ti-O-Ti bond formation in gas phase. The highest deposition rate of 11 nm/min, which was two orders higher than that for the case of single gas plasma, was achieved in the case of mixture gas ratio of 20% oxygen and 80% hydrogen. Surface reaction due to the heated substrate did not affect the deposition rate though the film structure was remarkably changed. It was demonstrated that for RPE-CVD process, oxygen/hydrogen mixture gas plasma was effective for obtaining high deposition rate, and also H-to-OH radical density ratio was an important factor to control the deposition rate.
Growth and Characterization of Semicontinuous Metal Films by Pulsed Laser Ablation
Authors: So S.K. , Fong H.H. , Cheung N.H.
Published: April 2011

Semicontinuous metals films of copper and gold were grown on different substrates by pulsed laser ablation. The resistance and transmittance of these growing metal films were monitored in situ vs film thickness. Despite diverse experimental variations, it was found that both resistance and transmittance exhibited similar behaviors. Around percolation, the resistance exhibited a sharp drop whereas the transmittance exhibited a dip. In general, the onset of percolation depended on laser fluence and substrates. Under favorable conditions, metal films as thin as 1.5 nm would percolate.
STM investigation of energetic insertion during direct ion deposition
Authors: Pomeroy Joshua M. , Couture Aaron , Jacobsen Joachim , Cooper Barbara H. , Sethna J.P. , Brock Joel D.
Published: April 2011

Thin copper films have been deposited on single crystal copper substrates and characterized using a UHV Scanning Tunneling Microscope to probe the effect of atomic insertions during hyperthermal ion deposition. At low temperatures, atomic insertions are predicted to provide a net downhill current that offsets the roughening effect due to uphill “Schwoebel” currents leading to a net smoothing of the surface. Films have been grown at several different energies targeted to observe a crossover from insertion driven smoothing to adatom-vacancy dominated roughening. Copper thin films are deposited near 20 eV using a mass selected ion deposition system that allows precise control (+/− 2 eV) over the energy of constituent atoms. Experimental observations are compared with a sophisticated Kinetic Monte Carlo and Molecular Dynamics hybrid (KMC-MD) simulation.