bluuebunny/crossref_metadata_2025 huggingface dataset:
Development Of Transparent Lsco and Lscno Conductors for Optical Shutter Systems
Authors: Schwartz R. W. , Sebastian M. T. , Charoenwongsa M. , Dobberstein H.
Published: April 2011

We have prepared lanthanum strontium cobalt oxide (La0.50Sr0.50CoO3; LSCO 50/50) and lanthanum strontium cobalt nickel oxide (La0.50Sr0.50Co0.50Ni0.50O3; LSCNO) as candidate transparent electrodes for use in a shutter-based infrared sensor protection device. The shutter device requires that the electrode be transparent (80% transmission) and have moderate sheet resistance (300 ω/sq.). Because of the effects of film thickness on intrinsic material properties, such as resistivity and extinction coefficient, and simple engineering issues (i.e., the relationship between film thickness, resistance and transmission), films of various thicknesses were prepared to achieve an optimal balance of electrical and optical performance. van der Pauw measurements and FTIR spectroscopy were used to study thin film properties. The best LSCO films prepared demonstrated electrical (438 ω/sq.) and optical (68% transmission at 8 µm) properties that did not meet the target property goals for this application. However, the LSCNO films (of optimal thickness) offered performance (323 µ/sq. and 73% transmission) close to the device requirements.
Predominant Scattering Mechanism in Transparent Conductive Oxide Films
Authors: Meng Chen , Zhiliang Pei , Xi Wang , Cao Sun , Lishi Wen
Published: April 2011

Contributions of acoustical deformation scattering, ion impurity scattering and grain boundary potential scattering to the conductivity of TCO films have been calculated to discuss the predominant scattering mechanism, regardless of precise details of the preparation procedure. The results indicate that the effective mass of charge carriers has a strong dependence on carrier concentration. Based on the effective mass correction, as well as the carrier concentration-ionized impurity centers correction, scattering due to ion impurity has been developed to explain the upper limit of mobility or the lower limit of resistivity of TCO films. Two empirical expressions are introduced to depict the dependence of the upper limit of mobility and the lower limit of resistivity of TCO films on carrier concentration.
Electrical Characteristics of the Pt/SBT/TiO2/Si MFIS Structures with Thickness Variation of the SBT Film
Authors: Kim Ji-Woong , Lee Kwang-Yong , Choi Jae-Hoon , Oh Tae-Sung
Published: April 2011

Pt/Sr0.85Bi2.4Ta2O9/TiO2/Si structures were prepared with variation of the Sr0.85Bi2.4Ta2O9 (SBT) film thickness for MFIS-FET applications. After depositing TiO2 film of 10 nm thickness by reactive sputtering on Si(100) substrate as a buffer layer, SBT thin film of 210-400 nm thickness was prepared onto it by metal organic decomposition process. Regardless of the SBT film thickness, the Pt/SBT/TiO2/Si structures exhibited clockwise directional hysteresis, indicating well-defined ferroelectric switching behavior of the SBT films. While the memory window of the Pt/SBT/TiO2/Si MFIS structures increased with increasing the SBT film thickness, the maximum capacitance of the Pt/SBT/TiO2/Si MFIS structures decreased with increasing the SBT film thickness. The Pt/SBT(400 nm)/TiO2(10 nm)/Si structure exhibited a memory window of 1.3 V at ±5 V.
Doping Effects on CdO Thin Films
Authors: Li X. , Barnes T. , DeHart C. , King D. , Asher S. , Young M. , Gessert T.A. , Coutts T.J.
Published: April 2011

This paper reports the properties of undoped CdO films and CdO films doped with the group VII element F and the group IV element Sn. The CdO films are made by low-pressure chemical-vapor deposition. We observe that undoped CdO films can achieve a carrier concentration of 1021 cm−3, apparently by controlling the intrinsic defect. However, the electron mobility of these films is only around 2 cm2 V−1 s−1. With fluorine doping, an electron mobility of ∼260 cm2 V−1 s−1 has been achieved. However, low carrier concentration results because of the low solubility of F in CdO film. CdO films doped with both Sn and F demonstrate carrier concentrations of 1021 cm−3 and reasonable electron mobilities of around 20 cm2 V−1 s−1. Due to the small effective electron mass of CdO, a large Burstein-Moss shift is observed for films with high carrier concentration. The shift enables the fundamental absorption edges of undoped CdO films to reach 3.0 eV and 3.3 eV for films doped with both Sn and F.
The Mechanical Reliability of Sputter-Coated Indium Tin Oxide Polyester Substrates for Flexible Display and Touchscreen Applications
Authors: Cairns Darran R. , Paine David C. , Crawford Gregory P.
Published: April 2011

Indium tin oxide (ITO) films deposited on polyester substrates are a key material in the development of two exciting technologies, touchscreens and flexible liquid crystal displays. The new generation “plastic” displays and touchscreens must be flexible and robust, have excellent optical properties, and be inexpensive. We report on the mechanical and electrical reliability of ITO on a polyethylene terephthalate substrate (PET). We show that the mechanical behavior of the ITO film is dominated by the properties of the substrate and that the deformation of the substrate is mapped by the crack patterns in the ITO. This is most strongly evidenced in the simulated wear of a touchscreen where failure after >50000 pen strokes is primarily due to cracking of the ITO as a result of increased substrate deformation over time. In addition the mechanical reliability of the ITO layer is dependent on the film thickness. Cracking was observed in a 105 nm thick ITO film at a strain of 0.022 and for a 16.8 nm thick film at 0.003. The thickness and hence sheet resistance of the film effectively limits the maximum allowable deformation of the substrate and must be considered in the design of suitable display and touchscreen devices. In addition we report on the change in resistance with time-at- temperature and relate this to the shrinkage of the substrate.
Dielectric Properties and Leakage Current Characteristics of Al2O3 Thin Films with Thickness Variation
Authors: Choi Jae-Hoon , Kim Ji-Woong , Oh Tae-Sung
Published: April 2011

Dielectric properties and leakage current characteristics of the Al2O3 thin films, deposited by reactive sputtering at room temperature, have been investigated with variations of the O2 content in the sputtering gas and the film thickness. The Al2O3 films of 10-300 nm thickness were amorphous without depending on the O2 contents of 25-75% in the sputtering gas. Maximum dielectric constant was obtained for the Al2O3 film deposited with the sputtering gas of 50% O2 content. With reduction of the film thickness from 300 nm to 10 nm, dielectric constant decreased from 9.04 to 3.71 and tangent loss increased from 0.0035 to 0.0594, respectively. When the O2 content in the sputtering gas was higher than 50%, the Al2O3 films exhibited no shift of the flatband voltage in C-V curves. The leakage current density increased with increasing the film thickness, and the Al2O3 films thinner than 100 nm exhibited the leakage current densities lower than 10−6 A/cm up to 650 kV/cm.
Thin film combustible gas sensors based on Zinc Oxide
Authors: Nunes Patrícia , Fortunato Elvira
Published: April 2011

Sensitivity tests to reductive gases such as methane, hydrogen and ethane were performed on zinc oxide (ZnO) thin films. The highest value of sensitivity was obtained for the film with a high electrical resistivity and a low thickness. The variation of the operating temperature of the film leads to a significant change in the sensitivity of the sensor with an ideal operating temperature dependence of the gas used. The sensitivity of the ZnO thin films changes linear with the increase of the gas concentration. However these films seem to be more appropriated for the detection of hydrogen following by methane and than for ethane since the value of sensitivity obtained are higher and its variation with the gas concentration more pronounced.
Integration of Biaxially Aligned Conducting Oxides with Silicon using Ion-Beam Assisted Deposited MgO Templates
Authors: Emmert Luke A. , Park Bae-Ho , Groves James R. , DePaula Raymond F. , Jia Q.X. , Arendt Paul N.
Published: April 2011

Two conducting oxides, La0.5Sr0.5CoO3(LSCO) and SrRuO3, were deposited by pulsed laser ablation onto silicon substrates coated with biaxially textured MgO on an amorphous silicon nitride isolation layer. Comparison is made between templates using just 10 nm of ion-beam assisted deposited (IBAD) MgO and substrates with an additional 100 nm of homoepitaxial MgO. Both of these conducting oxide layers exhibited in-plane and out-of-plane texture, on the order of that obtained by the underlying MgO. The SrRuO3 was c-axis oriented on both substrates, but exhibited a slightly sharper out-of- plane texture when the homoepitaxial MgO layer was included. On the other hand, the LSCO showed only (100) orientation when deposited directly on the IBAD-MgO templates, whereas a significant (110) peak was observed for films on the homoepitaxial MgO. A simple calculation of the distribution of grain boundary angles, assuming a normal distribution of grains, is also presented.
Domain structure in LaFeO3 thin films and its role on exchange coupling
Authors: Seo Jin Won , Fompeyrine Jean , Siegwart Heinz , Locquet Jean-Pierre
Published: April 2011

The origin of the exchange bias between a ferro- and an antiferromagnet still is not fully resolved. Many structural parameters such as film thickness, roughness, domain size, domain walls, strain, dislocations, and surface defects play a role. To disentangle their individual contributions, one must correlate each of these structural effects with the exchange bias. Here we report our first such attempts using thin films of the antiferromagnetic orthoferrite LaFeO3 grown by molecular beam epitaxy. We investigate how the epitaxial relationship and strain affect the domain configuration as well as their size and orientation. Next, we explore how these different domains can pin ferromagnetic domains in exchange-coupled systems. We conclude that decreasing the domain size of the antiferromagnet leads to a higher exchange bias. The highest exchange bias was obtained for LaFeO3 films on MgO substrates.
Electronic Structures and Nature of Host Excitation in Gallates
Authors: Schmidt P. C. , Sticht J. , Stephan M. , Eyert V. , Mishra K. C.
Published: April 2011

It is an interesting exercise in materials science to explore simple rules relating the electronic properties of ternary systems to those of their binary constituents. In the present work, we have investigated the electronic structures of the large band gap gallates MGa2O4(M=Mg, Ca, Ba and Zn) and the corresponding binary oxides MO and Ga2O3. Using first-principles band structure methods, we find that the metal atoms in MO control the width of the O 2p-like valence band and the size of the optical band gap. Covalent metal-oxygen bonding is much more pronounced in Ga2O3 and leads to characteristic structure in the valence band density of states. These basic features are retained in the ternary compounds where the covalent admixture to the chemical bond is largest between Ga and O, and the transitions across the band gap involve the Ga2O3 sublattice.
Cerium Doped Garnet Phosphors for Application in White GaN-based LEDs
Authors: Wu Jennifer L. , Denbaars Steven P. , Srdanov Vojislav , Weinberg Henry
Published: April 2011

Recently, renewed interest has emerged for the development of visible light, down-converting phosphors for application in white light emitting diodes (LEDs). In such devices, a blue GaN LED can act as a primary light source, serving as an efficient pump to excite photoluminescence in a phosphor with subsequent emission occurring at lower energies. The combination of blue light from the LED chip and emission from the phosphor(s) produces white light. It was recently reported that a combinatorial approach to synthesize and screen potential inorganic phosphors for use in white LEDs could aid in identifying improved phosphors for blue to yellow down conversion. Solid state thin-film arrays (libraries) based on the garnet structure (A1−x,Bx)3−z(C1−y,Dy)5O12:Ce3+z, where A, B = Y, Gd, Lu, La; C., D = Al, Ga; x and y = 0 to 1.0; and z = 0.03, were synthesized, and x-ray diffraction was used to select library samples of the crystalline garnet phase. Libraries of these various garnets were then characterized spectroscopically and their properties compared to traditionally prepared bulk powder phosphors of similar composition. Emission and excitation trends show that as larger cations are substituted for Y (A = Y), emission and excitation are red-shifted and as larger cations are substituted for Al (C = Al), emission and excitation are blue-shifted. If smaller cations are substituted for Y and Al an opposite trend is observed. Temperature dependence photoluminescence measurements and emission/excitation trends are also examined.
Synthesis and optical characteristics of ZnGa2O4−xSx:Mn2+
Authors: Kim J.S. , Park H.L. , Kim G.C.
Published: April 2011

The first zinc gallium oxysulfides (ZnGa2O4−xSx) are synthesized and emission properties of ZnGa2O4−xSxand ZnGa2O4−xSx:Mn2+have been investigated. The sulfur in ZnGa2O4−xSxforms tetrahedrons and the cations in ZnGa2O4−xSxare randomly distributed between tetrahedrons and octahedrons such that ZnGa2O4structure can be viewed as a mixed spinel. The four-fold enhancement of the brightness of Mn2+emission can be the significant effect of forming oxysulfide in ZnGa2O4−xSx:Mn2+
Long-Term Cathodoluminescent Characterization of Thin-Film Oxide Phosphors in a Wide Range of Electron Excitation Densities
Authors: Bondar Vyacheslav D. , Felter Thomas E. , Hunt Charles E. , Dubov Yuri G. , Chakhovskoi Andrei G.
Published: April 2011

Long-term processes of cathodoluminescence degradation of thin film phosphors Zn2SiO4:Ti and Zn2GeO4:Mn were investigated in a wide range of e-beam energies, current and power densities. The time dependencies describing the decreasing of emission intensity have been found. At higher current densities of e-beam irradiation, the specific behavior of long-term degradation processes was observed, which is characterized by rapid initial degradation and a slower long term decrease. The most probable mechanisms are proposed for long-term processes of degradation in the investigated phosphors.
SPV Monitoring of Near Surface Doping – Role of Boron-Hydrogen Interaction; Boron Passivation and Reactivation
Authors: Marinskiy D. , Lagowski J.
Published: April 2011

Hydrogen is known to cause the passivation of boron acceptors after such processing steps as wet etching, reactive ion etching, sputter deposition of metal contacts, and Ar ion beam etching. Previous studies of this effect employed CV profiling, spreading resistance profiling, and SIMS measurements on samples diffused with deuterium. These methods are either destructive to the Si surface or require deposition of metal contact. In the present study we used a non-contact small signal ac-surface photovoltage technique, currentlyavailable in commercial diagnostic tools. Simultaneous measurements of the semiconductor surface barrier, Vsb, and the capacitance of the surface depletion layer, CD, give the concentration of boron acceptors in a submicron distance from the Si surface or Si/SiO2 interface. The technique has proven very successful in monitoring low dose implants and also near surface doping in oxidized wafers. Inbare silicon wafers the method occasionally indicated surface boron concentration noticeably below the bulk value. We found such behavior in wafers after the chemical cleaning, used to prepare a hydrogen terminated surface. Thermal annealing at temperatures from 150°C to 200°C reactivates the boron dopant. We will discuss the effect of various cleaning and annealing conditions on passivation and reactivation of boron acceptors in the near surface region. The results obtained with the non-contact SPV technique show excellent agreement with previous studies. They also provide a basis for reliable measurement of the boron concentration free of interference from hydrogen passivation.
Shallow Junctions for Sub-100 Nm Cmos Technology
Authors: Meyssen Veerle , Stolk Peter , van Zijl Jeroen , van Berkum Jurgen , van de Wijgert Willem , Lindsay Richard , Dachs Charles , Mannino Giovanni , Cowern Nick
Published: April 2011

This paper studies the use of ion implantation and rapid thermal annealing for the fabrication of shallow junctions in sub-100 nm CMOS technology. Spike annealing recipes were optimized on the basis of delta-doping diffusion experiments and shallow junction characteristics. In addition, using GeF2 pre-amorphization implants in combination with low-energy BF2 and spike annealing, p-type junctions depths of 30 nm were obtained with sheet resistances as low as 390 Ω/sq. The combined finetuning of implantation and annealing conditions is expected to enable junction scaling into the 70-nm CMOS technology node.
The Role of Ion Mass on End-of-Range Damage in Shallow Preamorphizing Silicon
Authors: Clark Mark H. , Jones Kevin S. , Haynes Tony E. , Barbour Charles J. , Minor Kenneth G. , Andideh Ebrahim
Published: April 2011

Preamorphization is commonly used to form shallow junction in silicon CMOS devices. The purposeof this experiment was to study the effect of the preamorphizing species' mass on the interstitial concentration at the end-of-range (EOR). Isovalent species of Si, Ge, Sn and Pb were compared. Silicon wafers with a buried boron marker layer (4700 Å deep) were amorphized using implants of 22 keV 28Si+, 32 keV73Ge+, 40 keV 119Sn+ or 45 keV 207Pb+, which resulted in similar amorphous layer depths. All species were implanted at a dose of 5×1014 /cm2. Cross-sectional transmission electron microscopy (XTEM) was used tomeasure amorphous layer depths (approximately 400 Å). Post-implantation anneals were performed at 750 °C for 15 minutes. Plan-view transmission electron microscopy (PTEM) was used to observe and quantify the EOR defect population upon annealing. Secondary ion mass spectrometry (SIMS) was used to monitor the transient enhanced diffusion (TED) of the buried boron marker layer resulting from the EOR damage introduced by the amorphizing implants. Based upon the SIMS results Florida Object Oriented Process Simulator (FLOOPS) calculated the resulting time average diffusivity enhancements. Results showed that increasing the ion mass over a significant range (28 to 207 AMU) not only affects the quantity and type of damage that occurs at the EOR, but results in a reduced diffusivity enhancement.
Nonmelt Laser Annealing of 1 Kev Boron Implanted Silicon
Authors: Earles Susan , Law Mark , Jones Kevin , Talwar Somit , Corcoran Sean
Published: April 2011

Heavily-doped, ultra-shallow junctions in boron implanted silicon using pulsed laser annealing have been created. Laser energy in the nonmelt regime has been supplied to the silicon surface at a ramp rategreater than 1010°C/sec. This rapid ramp rate will help decrease dopant diffusion while supplying enough energy to the surface to produce dopant activation. High-dose, non-amorphizing 1 keV, 1e15 ions/cm2 boron is used. Four-point probe measurements (FPP) show a drop in sheet resistance withnonmelt laser annealing (NLA) alone. Transmission electron microscopy (TEM) shows the NLA dramatically affects the defect nucleation resulting in fewer defects with post annealing. Hall mobility and secondary ion mass spectroscopy (SIMS) results are also shown.
Evolution Of Defects Induced By High Energy He Implantation In Gold-Diffused Silicon
Authors: Bouayadi R. El , Regula G. , Pichaud B. , Lancin M. , Simon J. J. , Ntsoenzok E.
Published: April 2011

Silicon samples were gold-diffused at different temperatures, implanted with He ions at 1.6 MeVand then annealed at 1050°C for 2 hours. The implantation induced-defect structure and their distributionin the depth of the sample, studied by conventional and high resolution cross section electron microscopy (HRXTEM) depend on the gold level introduced in the wafer prior to the gettering process. A high concentration of gold in silicon seems to influence the defect configuration in the cavity zone. Indeed, gold chemisorbed atcavities can homogenize the surface energy of their planes in different orientations, and can increase the cavity critical diameter beyond they become facetted. Secondary ion mass spectroscopy (SIMS) profiles exhibit ashouldered shape and a width closely related to the presence of the defects (observed by XTEM) which are veryefficient sinks both for gold and copper atoms. Unfortunately, the electrical improvement of the material (checked by minority carriers diffusion length measurements MCDL) is not achieved by this gettering process, probably due to the high metal impurity concentrations remaining out of the gettering zone, to the presence of AuCu complexes and η-Cu3Si precipitates identified by deep level transient spectroscopy (DLTS)measurements and HRXTEM observations respectively.
Defect Evolution from Low Energy, Amorphizing, Germanium Implants on Silicon
Authors: Gutierrez Andres F. , Jones Kevin S. , Downey Daniel F.
Published: April 2011

Plan-view transmission electron microscopy (PTEM) was used to characterize defect evolution upon annealing of low-to-medium energy, 5-30 keV, germanium implants into silicon. The implant dose was 1 × 1015 ions/cm2, sufficient for surface amorphization. Annealing of the samples was done at 750 °C in nitrogen ambient by both rapid thermal annealing (RTA) and conventional furnace, and the time was varied from 10 seconds to 360 minutes. Results indicate that as the energy drops from 30 keV to 5 keV, an alternate path of excess interstitials evolution may exist. For higher implant energies, the interstitials evolve from clusters to {311}'s to loops as has been previously reported. However, as the energy drops to 5 keV, the interstitials evolve from clusters to small, unstable dislocation loops which dissolve and disappear within a narrow time window, with no {311}'s forming. These results imply there is an alternate evolutionary pathway for {311} dissolution during transient enhanced diffusion (TED) for these ultra-low energy implants.
Carbon Diffusion and Clustering in SiGeC Layers Under Thermal Oxidation
Authors: Salvador D. De , Napolitani E. , Coati A. , Berti M. , Drigo A.V. , Carroll M. , Sturm J.C. , Stangl J. , Bauer G. , Lazzarini L.
Published: April 2011

In this work we investigated the diffusion and clustering of supersaturated substitutional carbon 200nm thick SiGeC layers buried under a silicon cap layer of 40nm. The samples were annealed in inert (N2) or oxidizing (O2) ambient at 850°C for times ranging from 2 to 10 hours. The silicon self-interstitial (I) flux coming from the surface under oxidation enhances the C diffusion with respect to the N2 annealed samples. In the early stages of the oxidation process, carbon escape by diffusion across the layer/cap interface dominates. This phenomenon saturates after an initial period (2-4h) which depends on the C concentration. This saturation is due to the formation and growth of C containing precipitates which are promoted by the I injection and act as a sink for mobile C atoms. The competition between clustering and diffusion is discussed for two different C concentrations.
Implant Dose and Spike Anneal Temperature Relationships
Authors: Bourdelle K. K. , Fiory A. T. , Gossmann H.-J. L. , McCoy S. P.
Published: April 2011

The method of ion implantation and spike annealing for preparing shallow junctions suitable for the extension regions bridging the channel and source/drain contacts of CMOS transistors are studied by annealing blanket implants. Junction depths at a given sheet resistance for low energy B implants are minimized for the combination of a fast ramp with a sharp-spike anneal. This is shown to be physically based on activation energy phenomenology. The fraction of electrically activated B is insensitive to implant dose, unlike the case of transient enhanced diffusion. Arsenic implants show higher activation fraction than comparably annealed P implants, without the large transient enhanced diffusion which is attributed to P and Si-interstitial coupled diffusion. For targeted sheet resistance and junction depth, spiking temperature trends lower with implant dose, concomitant with decreasing fraction of activated dopant.
Reverse Diode Leakage in Spike-Annealed Ultra-Shallowjunctions
Authors: Gossmann Hans-Joachim L. , Feng Tao , Agarwal Aditya , Frisella Peter , Rubin Leonard M.
Published: April 2011

We have investigated diode leakage in junctions produced by ion-implantation of B with energies of 0.5 - 2 keV and doses of 2 × 1014 — 2 × 1015 cm−2 into n-type wells of ∼1 × 1018 cm−3, after rapid-thermal anneals (RTA) in lamp-based and hot-wall furnaces. Junc- tions are as shallow as 30nm and were directly probed to avoid complications arising from metalization. The leakage current, Ilkg, was found to be independent of the implant dose at any reverse voltage (-1 and -5 V). This implies that the electrically active defects are sufficiently far removed and on the surface-side of the junction. In both systems, a spike anneal (no intentional dwell time at peak-temperature) resulted in higher Ilkg than a soak anneal (dwell time of several seconds at peak-temperature). However, for the same spike annealing recipe, the hot-wall RTA produces tighter distributions than the lamp-based RTA. The width of the distribution is a mea- sure of the temperature uniformity across the wafer. Best leakage currents are of the order 1 × 10−6 A/cm2, in good agreement with device simulations The shallowest junctions exhibit Ilkg ∼5 × 10−4 A/cm2, still well below the specification of even the low power transistor of a 100 nm technology.
Boron Solubility Limits Following Low Temperature Solid Phase Epitaxial Regrowth
Authors: Lindfors C. D. , Jones K. S. , Rendon M. J.
Published: April 2011

The work described herein focuses on examining the effect of solid phase epitaxial regrowth (SPER) on boron implanted silicon. It is shown that boron levels within the silicon can greatly enhance or reduce the regrowth rate of the silicon. Electrical measurements show optimum sheet resistances for 5 keV, 2×1015 cm−2 implant conditions yielding sheet resistance values of ∼140 Ω/sq at 500 °C annealing to ∼120 Ω/sq at 650 °C. Results using Hall effect and four-point probe show lower doses of boron will become fully active but levels will drop significantly as dose is increased. Lastly, maximum active concentrations of boron appear to reach values of ∼3-4×1020 cm−3 for a boron dose of 1×1015 cm−2 after SPER. Lower SPER anneal temperatures or higher doses tend to activate less boron.
Effects of Nano-scale Colloidal Abrasive Particle Size on SiO2 by Chemical Mechanical Polishing
Authors: Zhou Chunhong , Shan Lei , Ng S.H. , Hight Robert , Paszkowski Andrew. J. , Danyluk S.
Published: April 2011

This paper reports on the effect of colloidal abrasive particle size in the polishing of thermally grown silicon dioxide on 100mm diameter, P-type, (100), single crystal silicon wafers. The abrasive particle sizes were varied in six (6) slurries with pH values of 10.97 ± 0.08. The abrasive sizes were 10, 20, 50, 80, 110 and 140nm in diameter, and the slurry contained 30 weight percent abrasives. The experimental results indicate that the material removal rate (MRR) varies with the volume of the particle size. Results also confirm that there exists an optimum abrasive particle size with respect to material removal rate and surface finish. For a pad surface roughness of 5.2μm (Ra), the slurry containing 80nm particles resulted in the highest material removal rate and best surface finish. A nano-film model based on the pad roughness is used to explain the results.
Engineered porous and coated Silica particulates for CMP applications
Authors: Choi K.S. , Vacassy R. , Bassim N. , Singh R. K.
Published: April 2011

The aim of this study has been to synthesize the microporous silica spheres and to coat as-synthesized SiO2 with CeO2 for CMP applications. First, spherical microporous silica powders with a narrow size distribution have been prepared by a precipitation technique involving the hydrolysis reaction of a silicon alkoxide in ethanol. The interparticle microporosity has been created by adsorption of an organic compound (glycerol) as the porogen. The presence of glycerol during the synthesis affects considerably the precipitation mechanism and its effect on the particle size will be discussed. The synthesis of silica microporous spheres of narrow size distribution yielded the preparation, by varying particle size and porosity, of a wide range of aqueous silica slurries. The influence of particle size, particle size distribution, porosity and particle concentration will be discussed in chemical mechanical polishing applications. Although silica particles show large plastic deformation than the bulk material, very good glass polishing rates are obtained due to the plastic deformation of the silica layer during CMP. Silica particles are suitable candidates for application in CMP because silica can be directly precipitated as monodispersed spheres, their narrow size distribution being an important requirement in CMP applications. Secondly, as-synthesized silica particles were coated with the cerium dioxide particles having hexagonal shape, which were precipitated by decomposition from the cerium precursors. For this study, three coating processes were introduced to investigate the best coating parameters. Improvements in CMP of glass were also obtained by coating silica particles with cerium oxide nanoparticles.
Polishing and Cleaning of Low K Dielectric Material for ild and Damascene
Authors: Wang Yuchun , Bajaj Rajeev , Moon Yongsik , Mai David , Wijekoon Kapila , Chen Yufei , Redeker Fritz
Published: April 2011

This paper describes CMP challenges in development of copper-low k process technology. As copper/oxide or copper/FSG backend schemes are being implemented successfully in early manufacturing, development focus has shifted to Cu/OSG (organo-silicate glass) integration development. Cu-OSG presents unique challenges with CMP integration, as these films tend to have much lower hardness than silicon dioxide. Significant process challenges have to be overcome prior to successfully implementing CMP process which does not mechanically damage the softer films and at the same time can achieve planarization requirements expected from CMP process. In addition, the OSG films tend to be hydrophobic leading to a need for developing improved cleaning processes/consumables. It was determined that Applied Materials ElectraPolishTM barrier slurry is extendable to OSG films. Good removal rate and removal profile can be achieved with ElectraPolishTM slurry. A proprietary cleaning solution reduced defect counts by 2 orders of magnitude as detected by SurfScan SS6200 on blanket OSG wafers. The same cleaning solution can be applied to copper/low-k patterned damascene wafers to clean both copper and dielectric surface. Polished OSG films have RMS roughness less than 2 angstroms and copper surface roughness about 5 angstroms with good surface finish. Blanket and patterned wafer results are presented to demonstrate final capability. Future directions for process enhancement are suggested.
An Integrated Molecular Dynamics and Monte Carlo Approach to Study Epitaxial Deposition of Silicon
Authors: Somasi Sweta , Khomami Bamin , Lovett Ronald
Published: April 2011

The length and time scales of an atomistic simulation are often too small for any direct comparison with experimental observations. In order to study the coverage of pits (COPs) found on the Si (100) surface by epitaxial deposition, we first calculate rate of individual steps using molecular dynamics and then define a sequence of Monte-Carlo steps to study the effect of various factors on effective coverage of COPs.
Atomic Assembly of Giant Magnetoresistive Multilayers
Authors: Wadley Haydn N.G. , Zhou Xiaowang , Johnson Robert A.
Published: April 2011

The emergence of metal multilayers that exhibit giant magnetoresistance (GMR) has led to new magnetic field sensors, and approaches for nonvolatile random access memories. Controlling the atomic scale structure across the many interfaces within these multilayers is central to improve the performance of these devices. However, the ability to manipulate atomic arrangements at this scale requires an understanding of the mechanisms that control heterometal film growth during vapor deposition. It is important to develop methods that enable prediction of the effects of deposition conditions upon this structure. Atomistic simulation approaches have been combined with deposition reactor models to achieve this. We have applied these approaches to analyze the atomic scale structure of sputter deposited CoFe/Cu/CoFe giant magnetoresistive multilayers similar to those used for magnetic field sensing. Significant intermixing is revealed at the CoFe-on-Cu interface, but not at the Cu-on-CoFe interface. Recent experiments verified these predictions. The insights provide a basis for the development of processes that inhibit thermally activated atomic diffusion while allowing the controlled use of the metal atom impact energy and inert gas ions to manipulate the structure of interfaces.
Nanoindentation and Microstructural Evolution Studies of DC Magnetron Sputtered Chromium Nitride Thin Films
Authors: Agarwal A.B. , Rainey B.A. , Yalisove S.M. , Bilello J.C.
Published: April 2011

Nanoindentation experiments have been performed to assess the mechanical behavior of chromium nitride (CrxNy) thin films sputtered in different deposition geometries and with varying Ar and N2 pressures. The hardness and elastic modulus of chromium nitrides are of great interest with regard to their applications. In the present work, two different deposition geometries, i.e. multi-substrate and confocal, were used to sputter (DC magnetron) a CrxNy layer on Si (100) wafers at varying nitrogen flow rates. The results of the nanoindentation experiments indicate that, over a similar argon and nitrogen regime, the CrxNy films grown in a multi- substrate geometry exhibit higher hardness and elastic modulus on the average than those grown in the confocal geometry. Furthermore, it was found that in the multi-substrate geometry the hardness and elastic modulus of the films were significantly higher than those in the confocally deposited films for a specific regime of the nitrogen flow rate (10-14 sccm). Finally, observations of the mechanical properties trends could be correlated with a higher degree of anisotropic stress for films grown in the multi-substrate in comparison to the confocal geometry.
Effect Of RTA On TiN Films As The Barrier Layer for Pt/BST/Pt Capacitors Prepared By RF Magnetron Co-sputter Technique At Low Substrate Temperature
Authors: Juang Miin-Horng , Hwang Chuan-Chou , Cheng Huang-Chung
Published: April 2011

Effect of rapid-thermal-annealing on metallic barrier TiN against the interdiffusions of Ti and Si into BST in Pt/BST/Pt/TiN/Ti/Si capacitors has been studied. In the integration of BST capacitors, the thermal budget of the BST deposition would cause the inter-diffusions of Ti and Si from Ti adhesion layer and Si-plug respectively. This event would degrade the BST capacitors. To address this issue, rapid-thermal-annealed TiN barriers were used between the bottom electrode Pt and adhesion layer Ti. Optimal RTA condition for TiN were found in this experiment. Excellent electrical characteristics of Pt/BST/Pt/TiN/Ti/Si capacitors, including high dielectric constant (εr =320), low leakage current (1.5×10−8 A/cm2) under 0.1 MV/cm, and life time longer than 10 year lifetime under 1.6 MV/cm were obtained with Ar+O2 mixed ambient at a low substrate temperature (300°C).
Microstructure and Surface Evolution in the Crystallization of α-Fe2O3/α-Al2O3(0001) Thin Films
Authors: Cho Tae Sik , Doh Seok Joo , Je Jung Ho
Published: April 2011

We found the correlation between microstructure and surface evolution in the crystallization of amorphous α-Fe2O3/α-Al2O3(0001) thin films using real-time synchrotron x-ray scattering and atomic force microscope. The amorphous precursor is crystallized to the epitaxial α-Fe2O3 grains in three steps; i) the growth of the well aligned α-Fe2O3 interfacial islands on α-Al2O3(0001), ii) the growth of the misaligned, homoepitaxial, α-Fe2O3 grains on the well aligned grains ( > 400 °C), and iii) the nucleation of the heteroepitaxial misaligned grains directly on the α-Al2O3substrate ( > 600 °C). The surface roughing is caused by the microstructure evolution during the crystallization of the amorphous precursor films.
The size effect of the polarization of SrBi2Ta2-xNbxO9 Capacitor
Authors: Tanaka Keisuke , Azuma Masamichi , Shimada Yasuhiro , Otsuki Tatsuo , Araujo Carlos A. Paz de
Published: April 2011

It is known that the ferroelectric characteristic drastically changes between the bulk crystal state and the thin film state, fabricated for the high density FeRAM. Therefore, the theoretical clarification of the high density FeRAM characteristic has become very important to realize the next generation FeRAM devices on time.

The size dependence of the polarization of SrBi2Ta2-xNbxO9 (SBTN) ferroelectric capacitor was calculated in the two-dimensional capacitor system considered with two different mechanisms, the depolarization effect and the surface effect due to the change of the long-range interaction between the polarization in the vicinity of the surface and interface. The free energy expression of thepolarization is described as a function of position of polarization using the Landau phenomenological theory.

The simulations of the size effect of the polarization were performed. The simulated result shows that the polarization is stable down to capacitor size of 0.01um2 which can be applied for next generation FeRAM devices.
Pulsed-Laser Deposition of TiNi Shape Memory Alloy Thin Films
Authors: Chen X.Y. , Lu Y.F. , Ren Z.M. , Zhang L. , Wang J.P. , Liew T.Y.F.
Published: April 2011

Thin films of TiNi shape memory alloy (SMA) have been prepared by pulsed-laser deposition (PLD) at different substrate temperatures. The stoichiometry, crystallinity, and morphology of the deposited films were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and atom force microscopy (AFM). The transformation behavior and crystallization temperatures were investigated by differential scanning calorimetry (DSC). It is found that the Ni content of the deposited films ranges from 46.7 to 52.0 at.%. The crystallization temperature of the amorphous films is around 460°C. The activation energy of the crystallization process is determined by Kissinger's method to be 301 kJ/mol. The martensitic transformation temperature of the annealed Ti-51.5 at.% Ni film is –20.8°C.
Correlations between island nucleation and grain growth for polycrystalline films
Authors: Eisenmenger-Sittner C. , Bergauer A.
Published: April 2011

For Physical Vapor Deposition (PVD) processes the nucleation and growth of stable islands on monocrystalline and even polycrystalline substrates can be described by the rate equation theory in a mean field approximation. The observable quantity which can be derived from the rate equations is the global density of stable islands. Interisland correlations and island size distributions, on the other hand, cannot be obtained from this formalism. The array of stable islands, in turn, forms the template for the subsequent growth of a polycrystalline thin film. For the initial grain shape and grain size therefore both, the global island density as well as possible interisland correlations play a key role.

This paper presents the results of simulations which take into account the effects of both, the global island density as well as island/island correlations on the growth of a thick polycrystalline film. The simulations consist of two steps: first a polycrystalline template is generated from an initial distribution of stable islands by employing an algorithm for the construction of Voronoi-zones. The Voronoi zone network mimics the state of the film just after island coalescence and just before the onset of grain growth. Then the well known q-state Potts model of grain growth is employed to study the further steps of microstructural evolution.

A higher initial island density leads to a faster onset of grain growth while a very homogenous distribution of islands significantly retards grain growth. The reasons for these effects are briefly discussed.
Formation Mechanism of Silica/Diblock Mesophases by Solvent Evaporation-Induced Self-Assembly
Authors: Yu Kui , Drewien Celeste A. , Hurd Alan J. , Brinker C. Jeffrey , Eisenberg Adi
Published: April 2011

Intermediate structures were trapped during the mesophase transition from lamellae to higher curvature structures in a sol-gel matrix. The target structures included normal hexagonally arranged cylinders and/or normal spheres in a cubic array distributed in a hydrophilic matrix. The present system is believed to be the first to trap these intermediates. Through solvent evaporation-induced self-assembly (EISA), mesostructured silica/diblock films with large characteristic length scales were prepared. The structure-directing agents were polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymers with high molecular weight, which are water insoluble and alcohol insoluble. We believe that no micellization took place in the present system; a disorder-to-order transition occurred due to the cooperative self- assembly of the diblock and silicates as the solvent preferentially evaporated from a film cast from a dilute homogeneous solution. During further preferential evaporation, the morphogenic effect of the increase of species concentration facilitates the mesophase development in the direction of a normal cubic to hexagonal to lamellar pathway. However, the morphogenic effects of both the decrease of the PS coil dimension and the siloxane condensation drive the mesophase development in opposite directions. The decrease of the PS coil dimension plays an important role in the present self-assembly process. Trapping of the intermediates and coexisting multiple mesophases are related to the facts that PS has high Tg and high hydrophobicity in particular, as well as to the fact that polymers have relatively low mobility in general.
Characterization of chemical and sensoric properties of ion-beam modified polyethersulfone layers
Authors: Sahre Karin , Eichhorn Klaus-Jochen , Simon Frank , Guenther Margaritha , Suchaneck Gunnar , Gerlach Gerald
Published: April 2011

Thin polyethersulfone (PES) films were irradiated with boron ions at doses between 1013-1016B+/cm2 and energies of 50, 130 and 180 keV. The induced changes of structural and optical properties were studied in detail. The influence on sensoric properties (moisture uptake, conductivity) was also in the focus of interest. The results of vibrational spectroscopy and X-ray photoelectron spectroscopy (XPS) indicate that in dependence on dose and energy of implanted boron ions the sulfone bonds are destroyed, and carbon-rich, amorphous and graphite-like structures are formed. This structural changes cause an increase of the conductivity of the surface films to a value of 10−8 Ω−1 at a dose of 1016 B+/cm2 from an as- prepared value of 10−15 Ω −1 and an increase of the saturation concentration during the moisture uptake.
Effects of substrates roughness on c-axis preferred orientation of ZnO films deposited by rf magnetron sputtering
Authors: Lee Jae Bin , Kwack Sanghyon , Kim Hyeong Joon
Published: April 2011

We investigated the effect of substrate surface roughness on c-axis preferred orientation of ZnO films deposited by radio frequency (rf) magnetron sputtering. We used as substrates a bare Si(100), evaporated Au/Si(100), evaporated Al/Si(100), and sputtered Al/Si(100), of which rms roughness by atomic force microscope (AFM) were 0.127, 1.71, 2.11, and 6.5∼11.8 nm, respectively. The crystallinity and the c-axis preferred orientation of ZnO films strongly depended on the surface roughness of the used substrates.
The Decomposition of tBAA on the Silicon Surface
Authors: Chang Che-Chen , Huang Ing-Jye
Published: April 2011

Among the copper precursors used, cupric β-diketonate complexes exhibit a high sublimationrate and a low pyrolysis temperature. This work explored the possibility of using a nonfluorinated t-butylacetato complex of Cu(II) as the precursor. Secondary ion mass spectrometry and temperature-program desorption studies on the adsorption and decomposition of the ligand, tert-butyl acetoacetate (tBAA), of this precursor on Si(100) showed that at low doses, all tBAA molecules dissociated readily upon adsorption on the surface at substrate temperatures as low as –160°C. For dissociation through tBAA bonding via the ester oxygen to the surface, the bond scission occurring at the tBu-O bond resulted in the formation of surface tert-butylfragments, which in turn underwent a β-hydride elimination reaction to yield isobutene and surface hydride. In addition, the bond scission occurring at the tBuO-CO bond produced surface tert-butoxy specie, of which the hydrogen atom in the â position can be transferred to the oxygen atom of the butoxy group to yield isobutene and surface hydroxyl species. Its implication in the quality of the copper film generated is discussed.
Exchange Coupling and Spin-Flip Transition of CoFe2O4/α-Fe2O3 Bilayered Films
Authors: Fujii Tatsuo , Yano Takuya , Nakanishi Makoto , Takada Jun
Published: April 2011

CoFe2O4/α-Fe2O3 (ferrimagnetic / antiferromagnetic) bilayered films were prepared on α-Al2O3(102) single-crystalline substrates by helicon plasma sputtering. A well-crystallized epitaxial α-Fe2O3(102) layer was formed on the substrate, while CoFe2O4 grown on α-Fe2O3(102) was a polycrystalline layer with a (100)-preferred orientation. The α-Fe2O3(102) films without CoFe2O4 layers clearly showed a spin-flip transition at about 400 K. The spins aligned perpendicular to the film plane at room temperature changed their direction within the film plane above 400 K. However the α-Fe2O3 base layers of CoFe2O4/α-Fe2O3 bilayered films did not show any spin-flip transition. The CoFe2O4 layer on α-Fe2O3 had a large in-plane magnetic anisotropy, while the spin axis of the α-Fe2O3(102) base layer was directed perpendicular to the film plane. The magnetization of ferrimagnetic CoFe2O4 layers was coupled perpendicularly to the spin axis of anitiferromagnetic α-Fe2O3 layers due to the exchange coupling at the interface between CoFe2O4 and α-Fe2O3.
Exchange-Biased Nio-Co Nanofaceted Bilayers Grown on MgO (110)
Authors: Dubourg S. , Bobo J.F. , Warot B. , Snoeck E. , Ousset J.C.
Published: April 2011

We have sputter-grown self-organised faceted NiO-Co epitaxial bilayers on MgO(110). Due to very close lattice parameters, NiO adopts the same NaCl crystallographic structure as the substrate but it minimises its surface energy growing in a stripe-shaped morphology elongated along [001] MgO direction. The Co layers then deposited on NiO adopt a fcc structure. They consist of a set of connected nanowires whose height is about 50 Å, length is near to 1 µm and lateral periodicity ≍ 100 Å. Magnetic properties of the Co layers were investigated by magneto-optical Kerr effect from 10 K to room temperature. They are dominated by a strong shape-induced uniaxial anisotropy and exchange coupling with the antiferromagnetic underlayer. Magnetisation loops recorded along the easy axis exhibit a perfect squareness and switch in a field range smaller than 10 Oe. Transverse measurements indicate that switching occurs by domain nucleation and/or domain wall propagation. On the contrary, close to the [110] hard axis, magnetic switching occurs by coherent rotation. The bi-stable Co magnetisation state along its easy axis has been used for ordering the NiO spins configuration from room temperature to 10 K. Sign and value of exchange bias induced by such a thermal treatment can be modulated thanks to a wide magnetocrystalline or local exchange path energies distributions.