bluuebunny/crossref_metadata_2025 huggingface dataset:
Parametric Characterization of Plasma Etching Processes
Authors: Mocela Michael T. , Jenkins Mary W. , Sawin Herbert H. , Allen Kenneth D.
Published: April 2011

The analysis of plasma etching processes has been explored for the etching of polysilicon films with CF3Cl/Ar discharges. The etching rate is well fit as a function of the macroscopic plasma parameters (power input, pressure, and composition) using Response Surface Methodology. The parametric expression obtained can be used to examine the sensitivity of the process to the operating conditions, and to optimize the process. The parametric expression also permits comparison of the experimental data with physically meaningful kinetic models.

The Response Surface Method allows characterization of a wide parameter space with few experiments. The design of the experimental set is critical to the success of the parametric fit. The parametric expression must account for interactions between parameters, and the expected curvature of the response surface will dictate the required number of data points.
Dry Etching for Nanometer-Scale Fabrication
Authors: Howard Richard E.
Published: April 2011

Conventional integrated circuit fabrication is currently making the transition from wet to dry etching in the effort to shrink feature sizes to about 1 micron. These plasma etching techniques, though, are not limited to micron dimensions; devices and structures smaller than 100 nm can be made. Using e-beam lithography and reactive ion etching, patterns down to about 20 nm have been made in tri-level stencils and in semiconductor substrates. Working silicon MOSFETs with gate widths down to about 30 nm have also been made. These MOSFET devices are so small that individual electron trapping events can be observed. These devices are being studied to give a better understanding of the physics of electronic conduction in small devices and better define the limits of microfabrication.
Correlation Between Plasma Excited States and Thin Film Characteristics in He-SiH4 PECVD
Authors: Ricard A. , Chouan Y. , Collobert D.
Published: April 2011

The excited states of He-5 % SiH4 PECVD have been analysed by emission and absorption spectroscopy.

Variations of spectral line intensities and He(23S) metastable densities have been correlated to the SiH over SiH2 bond ratio and to the deposition speed.

The best correlation has been found with the He excited states, specially He(23S) metastables : SiH films without SiH2 bonds have been obtained when the He(23S) densities reach a minimum value.
Chemical Vapor Deposition of Silicon Insulating Films Induced with a Perpendicular Electron Beam
Authors: Zarnani H. , Rocca J. J. , Bishop D. , Cody N. W. , Collins G. J.
Published: April 2011

SiO2 and Si3N4 thin films have been deposited at a substrate temperature of 350° using a glow discharge electron beam irradiating perpendicular to the wafer surface. Deposition rates up to 1000 Å/min and 250 Å/min respectively have been obtained. Films deposited over 4 inch diameter silicon wafers show uniformity of 5 percent. The deposition conditions and film properties are discussed.
Plasma Processing Reactor with Surface Magnetic Field Confinement
Authors: Mantei T. D. , Wicker T. E. , Kazmierzak D.
Published: April 2011

A plasma reactor has been developed for dry reactive plasma etching and thin semiconductor film deposition. The system combines a multipolar magnetic field layer [1] for charged-particle confinement, and independently controlled substrate biasing. A large volume of dense (1011 cm-3), uniform, quiescent plasma is produced at low working pressure ( 1 mTorr). Anisotropic profiles can be etched into silicon in an SF6-O2 plasma with vertical etch rates ∼l um/min. In a pure silane plasma, good quality polycrystalline silicon films can be deposited at rates 1 to 10 Å/sec., at substrate temperatures 50° to 300° C.
Nondestructive Characterization of RIE Induced Radiation Damage Using Surface Acoustic Wave
Authors: Gilboa H. , Hata W. , O'Donnell K. , Tabib-Azar M. , Das P.
Published: April 2011

Reactive ion etching (RIE) is extensively used as a high resolution pattern transfer process for fabrication of silicon devices. In this work dry etching radiation damage in p-type boron doped, silicon wafers was investigated using a nondestructive surface acoustic wave (SAW) technique. The transverse acoustoelectric voltage (TAV) is monitored across the silicon wafer which is placed in proximity of a SAW delay line. TAV is developed due to the nonlinear interaction between the electric field accompanying SAW and the free carriers near the silicon surface. TAV versus bias voltage (applied across the semiconductor) was obtained to measure the flatband voltage (VFB) shift. The flatband voltage shift of the etched wafer was determined as a measure of the amount of surface charge introduced into the surface by ion bombardment. SiO2films were etched in C4F8and C2H2with 2 W/cm2input power. The ion energy was determined by the self bias dc voltage developed on the cathode. It is shown that a magnetron RF discharge introduces an order of magnitude less damage than non-magnetron discharge.
Atomic Force Microscope-Based Lithography of Titanium
Authors: Gordon A. E. , Litfin D. D. , Hagedorn M. S. , Chen J. , Fayfield R. T. , Higman T. K.
Published: April 2011

Anodization of Ti by high electric fields at the tip of a scanned probe can be used to produce nanoscale features consisting of oxides of Ti. In this manner, Ti can be used as a sacrificial resist for nanoscale lithography by exploiting the etching selectivity differences between Ti and anodized Ti. The anodization was accomplished with an atomic force microscope using Ticoated silicon nitride cantilevers. The anodizing bias voltage is applied to the tip and is independent of the feedback, unlike the scanning tunneling microscope. With this setup we were able to fabricate sub-40 nm lines by direct anodization of Ti. It is also shown that once tip and sample are brought into hard contact, subsequent bending of the cantilever has little effect on the linewidth or thickness of the anodized material.
Fluorinated SiO2 Films For Interlayer Dielectrics In Quarter-Micron Ulsi Multilevel Interconnections
Authors: Homma Tetsuya
Published: April 2011

Fluorinated SiO2 films for use as interlayer dielectrics in ULSI multilevel interconnections are investigated. The interlayer dielectric film properties and their formation techniques have to meet the following requirements: (1) a low dielectric constant, (2) a high planarization capability, (3) a high capability for narrow gap filling, and (4) a low deposition temperature for low residual stress. To satisfy these requirements, three technologies have been investigated. They are: (i) a fluorinated SiO2 (SiOF) film by room temperature chemical vapor deposition (RTCVD-SiOF) using fluorotrialkoxysilane (FTAS) and pure water as gas sources, (ii) a room temperature liquid phase deposition (LPD) SiO2 film, and (iii) a fluorinated spin-on-glass (SOG) film by fluorotrialkoxysilane vapor treatment (FAST-SOG). The dielectric constant for SiO2 films can be reduced to 3.7 at 1 MHz by the RTCVD and LPD techniques. Although the FAST and RTCVD techniques cannot achieve full planarization, the LPD technique can achieve both global and local planarization because this technique has high capability for selective SiO2 film deposition. The RTCVD, FAST and LPD techniques have shown the possibility to reduce the film formation temperature to room temperature by catalytic reactions, resulting in low residual stress. Other properties of the RTCVD-SiOF, LPD-SiO2 and FAST-SOG films are good enough for the interlayer dielectric film application. The LPD-SiO2 film shows higher endurance properties to moisture than the RTCVD-SiOF and FAST-SOG films.
Real-Time Studies of The Electrocrystallization of Nanoscale Ceramic Superlattices
Authors: Golden Teresa D. , Phillips Richard J. , Switzer Jay A.
Published: April 2011

Electrodeposition is unique among thin film deposition techniques, since the current following a potential step from open circuit to a given overpotential (i.e., driving force) provides a real-time, in situ probe of the deposition process. We have used current-time transients to determine the kinetics and dimensionality of growth, and to calculatethe composition profiles of electrodeposited superlattices in the Pb-TI-O system. The transients are indicative of 2D growth, and the height of the 2D monolayer depends on the orientation of the film. A [100] oriented film has a step height of 0.13 nm and a [210] oriented film has a step height of 0.18 nm. These heights correspond to the (400) and (220) d-spacings, respectively. Using a Cottrell analysis, we were able to both calculate and tailor the composition profile in these superlattices. Superlattices grown by pulsing between 70 and 150 mV have square profiles, while those grown by pulsing between 70 and 230 mV have graded profiles.
An in Situ Electron Microscopy Technique for the Study of Thermally Activated Reactions in Multilayered Materials
Authors: Wall M.A. , Barbee T.W. , Weihs T.P.
Published: April 2011

A novel in situ transmission electron microscopy technique for the observation of reaction processes in multilayered materials is reported. The technique involves constantheating rate experiments of multilayered materials in image and diffraction modes. Because the fine scale microstructure of multilayered materials is typically a small fraction of the TEM specimen thickness, realistic comparison of the microstructural evolution with that of similarly processed thick foil samples is possible. Such experiments, when well designed, can provide rapid characterization of phase transformations and stability of nano-structured materials. The results of these experiments can be recorded in both video and micrograph format. The results and limitations of this technique will be shown for the Al/Zr and A1/Monel multilayered systems.
Structural Studies of Sputtered Ni80Co20/Cu Multilayers
Authors: Bian X. , Altounian Z. , Ström-Olsen J. O. , Sutton M. , Cochrane R. W.
Published: April 2011

The structure of magnetron-sputtered Ni80Co20/Cu multilayershas been investigated by low and high-angle X-ray diffractometry. Low-angle x-ray reflectivity data reveal well-defined compositional modulation along the film growth direction for a wide Cii thickness range of 5-40 Å. The data analysis, based on anl optical model, shows that interfacial mixing is limited to ∼3-4 Å As the number of bilayers increased from 8 to 100, the interface roughness increased by a factor of 3. Better layered structures were found for relatively thick Cu layers (tCu>10Å). The high-angle diffraction data were analyzed using a trapezoidal model. The results indicate that the films have a polycrystalline structure with a preferred (111)orientation with coherent interfaces of ∼ 100-240 Ådepending on the Cu layer thickness. The relatively large expansion of (111) spacings in NiCo alloy layers gives rise to the lower atomic ordering in NiCo/Cu multilayers.
Superconducting Multilayers: Microstructural Properties Studied by X-Ray Diffraction
Authors: Vailionis A. , Brazdeikis A. , FlodstrÖm A.S.
Published: April 2011

Structural properties of molecular beam epitaxy-grown Bi2Sr2Cu1Oy'Bi2Sr2Ca1Cu2Oy multilayers have been studied by x-ray diffraction. A one-dimensional kinematic x-ray diffraction model has been used to describe the structural quality of the multilayers. Interface roughness, stacking defects and unit cell disorder are obtained by an iterative fitting of the calculated diffraction profile to the experimental spectra. The type and amount of disorder in the films was qualitatively determined. Results demonstrate that structural imperfections are present in the multilayers and have to be considered when transport properties are studied.
Metal/Al2O3 Multilayers As High-Temperature X-Ray Mirrors
Authors: Morawe CH. , Zabel H.
Published: April 2011

By if-sputtering we have prepared high-quality metal/Al2O3 (metal: Co, Pt, W) artificial multilayers on sapphire (1120) substrates. We obtain interface roughnesses of about 0.2 nm and x-ray reflectivities of nearly 100 % at the first satellite reflection using Cu Kα radiation. The multilayer structures remain stable up to 700°C – 900°C without appreciable loss in reflectivity. Annealing causes structural changes depending on the chosen metal. Pt/Al2O3 forms a coherent superlattice structure whereas Co and W exhibit a gradual internal oxidation at the metal/Al2O3 interface. Beyond 900°C all systems are destroyed.
Compositional Characterization of Very Thin SiO2/Si3N4/SiO2 Stacked Films by XPS Using The “Auger Parameter Method”
Authors: Santucci S. , Lozzi L. , Passacantando M. , Picozzi P. , Alfonsetti R. , Fama F. , Moccia G.
Published: April 2011

ONO (SiO2/Si3N4/SiO2) structures with thickness less than 10 nm were deposited onto silicon wafers by successive steps using two different method. The effects of the forming time and temperature on the stoichiometry of the single layers and of the whole sandwich have been studied using X-ray Photoelectron Spectroscopy (XPS). This paper demonstrates that the “Auger parameter method” is highly suitable in quantifying the composition of very thin insulating structures.
Microstructural Characterization of Al-.5Cu AND Al-1Si ON 0.6nm TCA-SiO2/Si Following Heat Treatment at 400°C in N2 - Mechanisms Providing Stability and A High Break Down Voltage for The Al-.5Cu Mos Device
Authors: Mccarthy Jack M.
Published: April 2011

Al-.5Cu is used as an interconnect conductor in ultra large scale integration (ULSI) devices. The specific use investigated in this study is as a gate electrode deposited directly on extremely thin 6 nm TCA SiO2. Changes in microstructure and reactions between the AI-.5Cu and SiO2 following heat treatment were characterized using analytical electron microscopy. When Al-iSi or AI-.5Cu are used as gate electrodes in a metal oxide Si field effect transistor (MOSFET) a conducting diffusion barrier layer of TiN or heavily doped poly-Si is usually deposited between the AI alloy and the SiO2. The addition of this relatively high resistivity barrier layer increases the power consumption of a MOSFET constructed with this gate electrode, increases the operating voltage necessary and decreases the frequency at which the MOSFET can be switched.1 An Al-.5Cu metal oxide silicon (MOS) device maintained a high break down voltage without a diffusion barrier following heat treatment by forming an Al-Cu intermetallic at the silica/metal interface.
Solid State Reactions in the ZR-AL-CU-NI Bulk Metallic Glass Forming Alloy System
Authors: Busch Ralf , Bakke Eric , Johnson William L.
Published: April 2011

Diffusion couples combining a h.c.p. Zr90Al10 supersaturated solid solution with a fc.c. Cu64Ni36 solid solution were annealed at 410°C for different times. The reaction at the interface was investigated by transmission electron microscopy (TEM) and energy dispersive x-ray spectroscopy (EDAX). Cross sectional TEM images and electron diffraction patterns reveal the formation of a non-crystalline layer at the interface between the two solid solutions which grows to a maximum thickness of more than 0.3 μm. Using EDAX, the concentration profiles across the layerswere determined. The glassy layer consists of a Zr-Ni-Al alloy with a small amount of Cu.The concentration profiles reveal that two non-crystalline phases coexist in the diffusion couple. One phase is Ni-rich and the other is Zr-rich. A small gradient of the Ni concentration in the Ni-rich amorphous phase and a steeper gradient in the Zr-rich non crystalline phase indicate that the Ni diffusion constant in the Ni-rich phase is larger than the Ni diffusion constant in the Zr-rich phase. In the late stage of the reaction, the growth of a nanocrystalline layer with an average concentration of Cu 90Nij 0 is observed on the Cu-Ni side of the diffusion couple. Crystallization starts at the Zr-Al side of the diffusion couple.
Measuring the Adhesion of Diamond Thin Films to Substrates Using the Blister Test
Authors: Sizemore Jim , Hohlfelder R. J. , Vlassak J. J. , Nix W. D.
Published: April 2011

It is shown that the blister testing technique can be used to measure the adhesion of thin films to their substrates. A brief discussion of blister test mechanics is presented here, leading to a simple equation relating adhesion to the height of the blister and the pressure causing it to grow. Blister test data for plasma-enhanced CVD diamond films on Si substrates have been analyzed using this relation. The tests show adhesion energies of 1.8– 2.6 J/m2.
The Pressure-temperature Phase and Reaction Diagram for Carbon
Authors: Bundy Francis P.
Published: April 2011

Carbon atoms form very strong bonds to each other, yielding materials like: (i) crystalline graphite, diamond and their many “amorphous” hybrids; (ii) crystalline forms of giant closed–surface molecules such as the fullerenes; and (iii) liquid and gas phases which have molecular contents which are complicated and not yet defined or understood. Because of the high bonding energy the melting and vaporization temperatures of the solid forms are very high, and the activation energies required to transform one solid form to another are large. One consequence is that at lower temperatures the different solid phases may continue to exist metastably far into aP, Tregion in which another solid phase is the thermodynamically stable one.

In the thermodynamic sense the vapor pressure line of graphite, the graphite/liquid/vapor triple point, the graphite melting line, the graphite/diamond equilibrium line, and the graphite/diamond/liquid triple point are quite well established. Data for the melting temperature of diamond vs. pressure are sparse and rough, but they indicate that the melting temperature increases with pressure,-in agreement with some theories. Although carbon should transform to a solid metallic state at very high pressures, experimental evidence shows diamond to be stable to over 400GPa, and theoretical calculations indicate that it could be the stable form up to pressures of 1200 to 2300GPa. Attention is given to the solid state transformations which can take place when graphite is compressed and heated along differentP, Tpaths under different conditions.
Theory of some Carbon Solids
Authors: Cohen Marvin I.
Published: April 2011

Starting from properties of the carbon atom, it is possible to explore the structural stability and properties of various forms of carbon. A discussion of the theoretical approach and the relevant atomic characterisitcs will be given followed by example of applications to existing and hypothetical materials formed from carbon and related elements.
Adhesion of Polymers to Synthetic Diamond Films
Authors: Stromberg Earl W. , Drory Michael D.
Published: April 2011

A preliminary study of the adhesion of polymers to diamond substrates was conducted by examining the wetting characteristics of coupling agents to diamond. The contact angle between several commercial liquid coupling agents and a CVD diamond surface was measured. A silane, Z-6026, was found to wet the diamond surface. Several other coupling agents, including a titanate and an organometallic blend, wet the diamond surface significantly better than most of the other materials in this survey. It was found that water did not wet the diamond.
Molecular Dynamics Simulation of Mechanical Deformation of Ultra-Thin Amorphous Carbon Films
Authors: Glosli J. N. , Philpott M. R. , Belak J.
Published: April 2011

Amorphous carbon films approximately 20nm thick are used throughout the computer industry as protective coatings on magnetic storage disks. The structure and function of this family of materials at the atomic level is poorly understood. Recently, we simulated the growth of a:C and a:CH films 1 to 5 nm thick using Brenner's bond-order potential model with added torsional energy terms. The microstructure shows a propensity towards graphitic structures at low deposition energy (<1eV) and towards higher density and diamond-like structures at higher deposition energy (>20eV). In this paper we present simulations of the evolution of this microstructure for the dense 20eV films during a simulated indentation by a hard diamond tip. We also simulate sliding the tip across the surface to study dynamical processes like friction, energy transport and microstructure evolution during sliding.
Nanoindentation and Nanoscratching of Hard Carbon Coatings for Magnetic Disks
Authors: Tsui T. Y. , Pharr G. M. , Oliver W. C. , Bhatia C. S. , White R. L. , Anders S. , Anders A. , Brown I. G.
Published: April 2011

Nanoindentation and nanoscratching experiments have been performed to assess the mechanical properties of several carbon thin films with potential application as wear resistant coatings for magnetic disks. These include three hydrogenated-carbon films prepared by sputter deposition in a H2/Ar gas mixture (hydrogen contents of 20, 34, and 40 atomic %) and a pure carbon film prepared by cathodic-arc plasma techniques. Each film was deposited on a silicon substrate to thickness of about 300 nm. The hardness and elastic modulus were measured using nanoindentation methods, and ultra-low load scratch tests were used to assess the scratch resistance of the films and measure friction coefficients. The results show that the hardness, elastic modulus, and scratch resistance of the 20% and 34% hydrogenated films are significantly greater than the 40% film, thereby showing that there is a limit to the amount of hydrogen producing beneficial effects. The cathodic-arc film, with a hardness of greater than 59 GPa, is considerably harder than any of the hydrogenated films and has a superior scratch resistance.
Monte Carlo Simulation of Optical Temperature Sensors in RTP Systems
Authors: Cole J. Vernon , Knutson Karson L. , Fiory Anthony T. , Jensen Klavs F.
Published: April 2011

We present simulation and experimental results for determining the distribution of radiation throughout an RTP system and evaluating the design of optical temperature sensors. The simulations are performed with a general purpose, three dimensional Monte Carlo method. The simulation models internal reflection, absorption, and transmission within participating media explicitly, and includes wavelength, temperature, and material dependent properties. Simulation results are compared to measurements of the lamp intensity profile within the lamphouse and at possible sensor locations. Simulations are used to examine the effect of several optical probe designs. The predicted responses of potential sensor designs resulting from these studies are presented.
Characteristics of Dielectrics Formed or Annealed in a Nitric Oxide Ambient
Authors: Harrison H. B. , Yao Z. -Q , Dimitrijev S. , Sweatman D. , Yeow Y. -T.
Published: April 2011

The resultant physical and electrical characteristics of dielectric layers grown or annealed in nitric oxide are presented. The layers formed or modified in nitric oxide are thinner but generally superior in quality to those grown in nitrous or dry oxide. The indications are that dielectrics formed or annealed in nitric oxide are a viable alternative to other techniques of producing ultra thin (≤ 5nm) dielectrics.
Rapid Thermal Oxidation of Heavily Doped Silicon for Advanced Solar Cell Processing
Authors: Sivoththaman S. , Laureys W. , Nijs J. , Mertens R.
Published: April 2011

Crucial steps in solar cell processing such as emitter diffusion and surface oxide passivation have been carried out by rapid thermal processing (RTP). Rapid thermal diffusion (RTD) of boron into silicon from APCVD borosilicates has been studied. Rapid thermal oxidation (RTO) of the heavily B-doped surfaces of these shallow junctions (0.2 μm) has been studied in view of applicability of this technique in solar cell processing. These shallow diffusions have excellent lateral uniformity over large areas and have high surface concentrations depending on the APCVD deposition conditions and on RTP conditions. The surface passivating oxides resulting from the RTO are exceptionally thick in case of heavy boron diffused surfaces. RTO does not cause considerable drive-in of the diffused junction profiles. In the contrary, the thick RTO oxides considerably reduce the surface concentration, thereby reducing the heavy doping effects in the junctions, making them more suitable emitters for devices such as solar cells. p+nn+ solar cells have been fabricated on n-type CZ silicon wafers by RTD of boron followed by RTO. The cells result in conversion efficiencies as high as 16.2% The passivation effect of RTO oxides have been investigated by analysing RTO MOS capacitors and are compared to conventional furnace oxides.
Characterizations of Ultra-thin Dielectrics Grown by Microwave Afterglow O2/N2O Plasma Oxidation at Low Temperature with Rapid Thermal Annealing
Authors: Chen Po-ching , Hsu Klaus Yung-jane , Loferski Joseph J. , Hwang Huey-liang
Published: April 2011

Microwave afterglow plasma oxidation at a low temperature (600 °C ) and rapid thermal annealing (RTA) were combined to grow high quality ultra-thin dielectrics. This new approach has a low thermal budget. The mid-gap interface state density of oxides pretreated in N2O plasma was decreased to about 5×1010 cm−2eV−1 after rapid thermal annealing at 950 °C.It was found that RTA is very effective for relieving the oxide stress and reducing the interface state density. Nitrogen incorporated in oxides by the N2O plasma pretreatment of the Si surface helped to reduce the interface state density. Microstructures of ultra-thin oxide grown by microwave afterglow oxidation with or without RTA were revealed by extended-X-ray-absorption-finestructure (EXAFS) and X-ray photoelectron spectroscopy (XPS) analysis.
The Necessity of RTCVD in Advanced Epitaxial Growth of Si and SiGe
Authors: Boer W. B. De , Theunissen M. J.J. , Linden R. H. J. Van Der
Published: April 2011

Device-quality epi material can be grown at temperatures ranging from 600 to 800°C in commercially available production reactors. The exceptionally steep transitions of Ge, B and, to a lesser extent, P, are characteristics of Si and strained SiGe epi growth from dichlorosilane and germane in hydrogen ambient at atmospheric or reduced pressure. Although the growth rates depend on the dopant gas flows at low temperatures, layer thickness and doping level control is excellent. Selective multilayer growth at reduced pressure seems a viable process and can be applied in e.g. HBT's.

In spite of the fact that a lot of the progress in low-temperature epitaxy has been made in lampheated reactors, it is argued that RTP is not needed for low-temperature epitaxy. This is in contrast to conventional (high-temperature) epitaxy where RTP is becoming indispensable. Real RTP, heating and cooling the wafer in just a couple of seconds, would improve the throughput of the present generation single wafer epi reactors tremendously and seems feasible.
Rapid Thermal Processing-Based Heteroepitaxy: Material and Device Challenges
Authors: Hoyt J. L. , Kuo P. , Rim K. , Welser J. J. , Emerson R. M. , Gibbons J. F.
Published: April 2011

Material and device challenges for Rapid Thermal Processing (RTP) of heterostructures are discussed, focusing on RTP-based epitaxy in the Si/Si1−xGex system. While RTP-based heteroepitaxy offers enhanced processing flexibility, it also poses significant challenges for temperature measurement and control. Several examples of Si/Si1−xGex device structures are discussed from the point of view of the sensitivity of device parameters to variations in layer thickness and composition. The measured growth kinetics for Si and Si1−xGex are then used to estimate growth temperature tolerances for these structures. Demanding applications are expected to require temperature control and uniformity to within 0.5°C.

Future research challenges include the fabrication of structures with monolayer thickness control using self-limited growth techniques. Atomic layer epitaxy (ALE) is a well-known example of such a growth technique. In ALE, the wafer is cyclically exposed to different reactants, to achieve layer-by-layer growth. An RTP-based atomic layer epitaxy process, and its application to the growth of CdTe films, is briefly discussed. The extension to Column IV alloys follows readily. The RTP-based process enables self-limited growth for precursor combinations for which isothermal ALE is not feasible.
Low Temperature Selective Silicon Epitaxy Using Si2H6, H2 and Cl2 in Ultra High Vacuum Rapid Thermal Chemical Vapor Deposition
Authors: Violette Katherine E. , Öztürk Mehmet C. , O'Neill Patricia A. , Christensen Kim , Maher Dennis M.
Published: April 2011

In this paper we present for the first time the use of the Si2H6/H2/Cl2 chemistry for selective silicon epitaxy in a rapid thermal CVD reactor. Depositions were carried out in an ultra-high vacuum rapid thermal chemical vapor deposition (UHV-RTCVD) system designed and constructed at North Carolina State University. Experiments were performed over a temperature range of 650°C to 850°C and over a pressure range of 22 to 25 mTorr using a flow rate 100 sccm of 10% Si2H6 in H2 and 0 to 10 sccm of Cl2. Deposited layer thicknesses were evaluated using a combination of interferometry and profilometry. Without Cl2 over the range of 650°C to 850°C, the growth rate is approximately constant at 160 nm/min. exhibiting a weak dependence on temperature. A clear advantage of Si2H6 is that high growth rates compatible with single wafer manufacturing can be obtained at very low pressures thus minimizing the introduction of contaminants by the process gases. With the addition of C12, the growth rate is suppressed at temperatures below 800°C, but, at 800°C and above, it is affected only slightly for Cl2 flow rates below 5 sccm. As the Cl2 flow rate is increased past 5 sccm, the growth rate at higher temperatures becomes a strong function of Si2H6:Cl2 ratio. Excellent selectivity with respect to patterned SiO2 and Si3N4 was obtained over the entire Cl2 flow rate range suggesting that even lower Cl levels may be sufficient for selective deposition. This implies that selectivity can be obtained with Si:Cl ratios much lower than those introduced by the more commonly used SiH2Cl2 chemistry. Furthermore, because Si2H6 can provide high growth rates at very low pressures, the total partial pressures of Cl2 and resulting chlorinated species can be significantly lower than typically required for selectivity. Our results indicate that C12 successfully enhances selectivity and yields highly selective depositions for process durations well within the practical limits of single wafer manufacturing.
Structural and Electrical Characterization of FeSix – Layers (1≤ X ≤2) Prepared by RTP of Fe Layers Sputtered on Si (100)
Authors: Líbezný M. , Poortmans J. , Amesz P. H. , Donaton R. A. , Larsen K. Kyllesbech , Vandenabeele P. , Jonckx F. , Maex K. , Nijs J.
Published: April 2011

β-FeSi2 is a semiconductor with a potential for photovoltaic and optoelectronic applications. The preparation of β-FeSi2-layers by rapid thermal processing (RTP) of Fe layers on silicon is investigated in this paper. Fe layers with typical thicknesses of 30 nm were sputtered on Si (100) substrates. We correlated the surface morphology of samples subjected to different RTP treatments with their composition and phase content. Phase transformations during the anneal were also studied by in-situ emissivity measurements. Rectifying and contacting behaviour of silicide/silicon heterojunctions prepared at several RTP-temperatures is presented at the end of this paper. Since it is not possible to prepare β-FeSi2-layers without a presence of either FeSi or α-FeSi2 metallic phases, these structures have poor heterojunction characteristics.
Effects and Applications of Multiple-Gas Rta Treatment on Ti-Based Metallization for Future Dram Devices
Authors: Drynan John M. , Koyama Kuniaki
Published: April 2011

The effects of N2, O2, and Ar gas RTA treatments on Ti, TiN, and Ti-polycide film characteristics have been investigated in anticipation of the trend in DRAM development toward lower resistance materials to replace the standard WSi2, WSi2 on doped polycrystalline silicon (W-polycide), and doped polysilicon conductors used in interconnections, transistor gates, and contact-hole plugs, respectively. The reactivities of Ti and TiN in N2 and O2 gases are markedly different. Film characteristics such as sheet resistance, crystallinity, and elemental composition remain unchanged for TiN RTA-treated in N2 but vary significantly for Ti. In the case of Ti, XRD and XPS data indicate the formation of intermediate Ti-rich TiN or Ti2N compounds prior to the final TiN phase. Similarly, RTO-treated TiN shows a slower oxide growth rate compared with that of Ti. In the case of TiN, a surface layer of rutile phase TiO2 is directly formed, whereas for Ti the data suggest the formation of Ti-rich oxides such as Ti2O or TiO prior to the final TiO2 rutile phase. RTA treatment in different ambient gases can be used to create multilayer Ti-polycide and TiN/Ti metallization with self-aligned TiO2 passivation and etch-stop layers. TiN can also be applied with other materials and processes to form new DRAM memory cell capacitor structures.
RTA-Treated Ohmic Contacts To GaAs Containing WSiN Barriers
Authors: Nebauer E. , Merkel U. , Würfl J. , Österle W.
Published: April 2011

For III-V device operation at 300 °C or above ohmic contacts have to consist of multilayered systems comprising an amorphous diffusion barrier. The contact system Au/Pt/Ti/WSiN/ Au/Ge/Ni-n-GaAs (n ≈ 5.1017 cm−3) has been developed and optimized with respect to the parameters of the barrier as well as the internal Au/Ge/Ni layers. The WSiN layer was deposited via reactive dc magnetron sputtering, the other layers by electron beam evaporation without breaking the vacuum. Annealing has been performed in a halogen lamp furnace. The contact resistance Rc as determined by TLM structures was measured as function of the annealing temperature and time. It was found that short-time annealings lead to a broad Rc minimum at 0.1 ωmm. For such Rc's the Au/Ge/Ni layer thicknesses must be ≥ 20/10/6 nm. Extended microstructural analysis was accomplished by XTEM/EDS and by AES and SNMS depth profiling. The typical alloying depth of the contact in the GaAs has been found to be about 50 nm, i.e. smaller than for the conventional Au/Ni/AuGe contact. The secondary phases formed (Au(Ga), NiGe(As)) are similar. With annealing conditions producing the desired Rc value, both Au(Ga) and NiGe(As) were observed in a bamboo-like arrangement at the metal-semiconductor interface. Degradation of Rc could be attributed to burying of the nickel-rich phases beneath gold-rich phases. This contact system is stable up to ≈ 300°C.
The Effect of Grain Boundaries on Surface Diffusion Mediated-Planarization of Polycrystalline Cu Films
Authors: Brain R.A. , Gardner D.S. , Fraser D.B. , Atwater H.A.
Published: April 2011

In situ, ultrahigh vacuum anneals were performed to induce Cu reflow at 500°C following deposition of Cu films and a Ta barrier layer on 1 μm wide by 1 μm deep trenches. Transmission electron micrograph cross-sections show profiles which suggest that grain boundaries and surface energy anisotropy significantly affect reflow. The extent of reflow is dependent on the structure of grain boundary-surface intersections, and the surface profile consists of regions of low curvature within grains and with sharp discontinuities in curvature at grain boundaries, a structure that inhibits surface diffusion. We present results showing how the surface diffusion mediated reflow varies with grain boundary groove angle and position, and compare these results with finite-element simulations that model surface diffusion-driven reflow.
Theoretical Investigation of Implanted Dopant Diffusion From a Silicide Layer to the Silicon Wafer for Ultra Shallow P-N Junction Formation
Authors: Sinder M. , Pelleg J.
Published: April 2011

In this work a theoretical model is presented to analyze the technique recently suggested to form shallow p-n junction. According to this technique a silicide acts as a source of a dopant and it is followed by controlled diffusion anneal to accomplish the dopant penetration into a silicon wafer.

In our analysis the dependence of the p-n junction depth on process parameters is discussed. The model considers two cases, namely, with and without dopant evaporation.

Experimental data for B diffusion from CoSi2 acting as the source are used to evaluate our theoretical model. The agreement between theoretical and experimental results is satisfactory.
Modeling, Simulation and Control of Single Wafer Process in Cluster Tool Base on Ft-Ir In-Line Sensor
Authors: Liu Shaohua , Solomon Peter , Carpio R. , Fowler B. , Simmons D. , Wang J. , Wise R. , Imper G. , Riley N.B. , Moslehi M. , Ravindra N.M.
Published: April 2011

This paper outlines our current approach to utilize infrared reflectance spectroscopy for thin film measurement in the semiconductor industry. The multi-layer thickness and doping concentration of IC wafers can be determined by a single angle, unpolarized infrared reflectance measurement performed using Fourier transform infrared spectrometer. A computer algorithm, which matches theoretical to measured infrared reflectance spectra, was successfully employed to determine multiple thin film properties.
Site Balance Models in Plasma Processing: A Comparison to Molecular Dynamics Simulations
Authors: Barone M.E. , Graves D.B.
Published: April 2011

Molecular dynamics (MD) simulations were conducted of Cl+ impact (at 10, 25 and 50 eV) of an initially bare silicon surface, leading to steady state coverage of Cl in a mixed chlorosilyl layer. Our main goal in this study was to compare the MD predictions to models of ion-assisted etching involving the concept of a site balance. For the case of 50 eV Cl+ etching silicon, the coverage vs. exposure results in the simulation could be reasonably well reproduced in a site balance model, but only if the correct parameters in the model were taken from the simulation. The results of the comparison suggest that MD simulations can be helpful in the development of physically sound phenomenological models of ion-assisted etching.
Hot-Carrier Effect in Submicron pMOSFETs
Authors: Saha S. , Yeh C. S. , Lindorfer Ph. , Luo J. , Nellore U. , Gadepally B.
Published: April 2011

This paper describes an application of process and device simulation programs in the study of substrate current generated by hot-carrier effect in submicron p-channel MOSFET devices. The impact ionization model for holes was calibrated for accurate simulation of substrate current in submicron devices, and an expression for the impact ionization rate of holes in silicon is obtained. The simulated substrate current for 0.57, 0.73 and 1.13 μm devices obtained by the optimized expression agrees very well with the measured data. The optimized impact ionization expression was also used to simulate the effect of p- Lightly Doped Drain impurity profile on substrate current, and the simulated peak substrate current and the corresponding maximum lateral channel electric field as a function of p- dose and length are presented.
Grain Boundary Migration and Grain Growth Induced by Electromigration in Copper and Aluminum Lines
Authors: Gladkikh A. , Glickman E. , Karpovsky M. , Lereah Y. , Palevski A. , Shubert J.
Published: April 2011

The changes of microstructure in Al and Cu thin film lines due to electromigration have been studied using transmission electron microscopy. Grain boundary migration, inclination and dislocation activity were found to be critically involved in the electromigration induced hillock formation that can be described as three dimensional grain growth.
The Effects of Deposition temperature on the Growth of Copper films produced by low pressure metal-organic chemical vapour deposition
Authors: Yoon S.S. , Kang S.W. , Chun S.S.
Published: April 2011

Copper was deposited onto TiN by low pressure metal-organic chemical vapour deposition, using hfacCu(I)TMVS and argon carrier gas. The effects of the deposition temperature on the growth of copper films were investigated by observing the surface morphology and the cross sectional morphology of copper films. At the initial stage of growth, copper films tended to have the island-like growth mode, irrespective of the deposition temperatures. It was also observed that the aspect ratio(=height to width) of the islands gradually increased as the deposition temperature increased. The poorer movability of the copper atoms at the higher deposition temperature was evaluated on the basis of hindering effect by the following copper deposits.
The Effects of Test Condition, Microstructure and Linewidth on Electromigration Void Morphology
Authors: Bauguess S. , Dreyer M. L. , Tucker M. , Theodore D. , Lee C. T. , Edwards S.
Published: April 2011

In this paper, experimental results for electromigration void morphology and failure time distribution are presented as a function of test condition, grain size distribution and conductor linewidth. Unpassivated Al-Cu(1.5%)-Si(1.5%) conductors with linewidths in the range lum ≤W ≤l0μm were subjected to accelerated temperature stresses of T=150° C and 250°C and current stresses in the range j= 0.5-4X106 A-cm-2, for each temperature stress. Unlike previous reports, erosion-like voids dominated at all current densities and temperatures for both W/D50≤1 and W/D50 > 1. The void distribution within a line was strongly dependent on test conditions and linewidth. The critical current density was extracted from electromigration lifetimes measured as a function of current density. The results show that the linewidth dependence of electromigration lifetimes depend strongly on the Blech relation.
Quantitative Measurement of Interface Fracture Energy in Multi-Layer Thin Film Structures
Authors: Ma Qing , Fujimoto Harry , Flinn Paul , Jain Vivek , Adibi-Rizi Farshid , Moghadam Farhad , Dauskardt Reinhold H.
Published: April 2011

Interfacial debonding of multi-layer thin film systems can severely affect the reliability of devices. To quantitatively evaluate the interface adhesion strength, a sandwich structure four-point bending technique was developed. In the sandwich structure samples, the thin film structure of interest was diffusion bonded between two silicon substrates. A fourpoint bending method was applied to propagate a crack along the interface of interest. Two thin film systems with nominally the same structure, but processed under different conditions, were measured for their SiO2/TiN interface fracture energies. Results showed that the interface fracture energy of one system was about 50% larger than that of the other system. Cross-section TEM observations revealed that the stronger interface was also significantly rougher.
Ionic Modeling of Lithium Manganese Spinel Materials for Use in Rechargeable Batteries
Authors: Cygan Randall T. , Westrich Henry R. , Doughty Daniel H.
Published: April 2011

In order to understand and evaluate materials for use in lithium ion rechargeable battery electrodes, we have modeled the crystal structures of various manganese oxide and lithium manganese oxide compounds. We have modeled the MnO2 polymorphs and several spinels with intermediate compositions based on the amount of lithium inserted into the tetrahedral site. Three-dimensional representations of the structures provide a basis for identifying site occupancies, coordinations, manganese valence, order-disorder, and potentially new dopants for enhanced cathode behavior. X-ray diffraction simulations of the crystal structures provide good agreement with observed patterns for synthesized samples. Ionic modeling of these materials consists of an energy minimization approach using Coulombic, repulsive, and van der Waals interactions. Modeling using electronic polarizabilities (shell model) allows a systematic analysis of changes in lattice energy, cell volume, and the relative stability of doped structures using ions such as aluminum, titanium, nickel, and cobalt.
Charge Transport Properties of a Partially Reduced V2O5 Xerogel Intercalated with a Polymer Electrolyte
Authors: Albritton Thomas Joyce , Kloster Grant M. , Shriver D. , Kannewurf C. R.
Published: April 2011

Recently, there has been considerable interest in advanced materials and processing techniques for practical applications. V2O5 xerogels have generated much attention because they are layered materials that undergo reversible redox intercalation with lithium. The sol-gel process has been used to intercalate V2O5 xerogels with the polymer electrolyte, oxymethylene linked poly(ethylene oxide) - lithium triflate [(a-PEO)n(LiCF3SO3)]. The resulting nanocomposite is a mixed ionic-electronic conductor in which the ionic charge carriers in the polymer electrolyte are in intimate contact with the electronic charge carriers in the V205 xerogel. Variable-temperature electronic conductivity and thermoelectric power measurements have been performed to examine the charge transport properties.
Design and Testing Criteria for Bipolar Plate Materials for Pem Fuel Cell Applications
Authors: Borup R. L. , Vanderborgh N. E.
Published: April 2011

Bipolar plates for proton exchange membrane (PEM) fuel cells are currently under development. These plates separate individual cells of the fuel cell stack, and thus must be sufficiently strong to support clamping forces, be electrically conducting, be fitted with flow channels for stack thermal control, be of a low permeability material to separate safely hydrogen and oxygen feed streams, be corrosion resistant, and be fitted with distribution channels to transfer the feed streams over the plate surface. To date, bipolar plate costs dominate stack costs, and therefore future materials need to meet strict cost targets.

A first step in the bipolar plate development program is an assessment of design constraints. Such constraints have been estimated and evaluated and are discussed here. Conclusions point to promising advanced materials, such as conductive, corrosion resistant coatings on metal substrates, as candidates for mass production of fuel cell bipolar plates. Possible candidate materials are identified, and testing procedures developed to determine suitability of various materials.
Development of Aluminosilicate Polyelectrolytes for Solid-State Battery Applications
Authors: Rawsky Glenn C. , Henretta Kevin J. , Lowrey Robert , Shrtver Duward F. , Vaynman Semyon
Published: April 2011

We have synthesized and characterized a range of novel polyelectrolytes containing weakly basic aluminosilicate anions in the polymer backbone in order to achieve t+ = 1 and high ionic mobility. Room-temperature conductivity is observed to increase in the series: [NaAl(OEOMe)2 ((OE)xO)2/2]n < [NaAl(OR)2(OSiMe2(CH2)3(OE)xO(CH2)3SiMe2O)2/2]n < [NaAl(OSiR3)(OSiMe2(CH2)3(OE)xO (CH2)3SiMe2O)3/2]n. This trend is ascribed to reduced ion pairing due to decreasing anion basicity, and lowered Tg resulting from increasing siloxy character. The addition of cryptand [2.2.2] increases conductivities by 1 -1.5 orders of magnitude. A maximum room-temperature conductivity is observed at a ratio of ≈10 etheric oxygens/cation. Related lithium polymer electrolytes were evaluated in mechanically joined solid state Li |PE |[LixMn2O4-C-PE] cells.