bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth and Characterization of Rare-Earth Phosphide/Arsenide Schottky Contacts to GaAs
Authors: Lee P. P. , Chem J. H. , Sadwick L. P. , Hwu R. J. , Balasubramaniam H. , Kumar B. R. , Alvis R. , Lareau R. L. , Streit D. C. 
Published: April 2011

ABSTRACTThe lack of high-temperature thermodynamically stable contacts has been a limiting factor for III-V compound semiconductor metallization. The instability of metal/semiconductor contacts at higher temperatures arises due to factors such as thermodynamic instability at the interface, lack of chemical inertness especially to oxygen containing ambients and a large lattice mismatch to the substrate. Our studies of two rare-earth compounds, dysprosium phosphide (DyP) and dysprosium arsenide (DyAs), demonstrate their potential to address the above problems. The growth and characterization of these two materials and their heterostructures will be presented.Both the DyP and DyAs epilayers were grown using MBD. DyP has an excellent room temperature lattice match to GaAs with a mismatch of about 0.01%, whereas DyAs has a lattice mismatch to GaAs on the order of about 2.4%. Consistent high quality DyP and good quality DyAs epilayers, as characterized by TEM, XRD, AES and AFM were obtained for growth temperatures between 500°C and 600°C. The growth rate was about 0.5 μm/hr and and the RMS roughness of the epilayer surface was typically about 0.5 nm and 1.3 nm for Dyp and DyAs, respectively.Electrical characterization of DyP and DyAs include variable temperature Hall measurements, four point probe, TLM, I-V and C-V measurements. Results show that both DyP and DyAs epilayers are n-type with electron concentration between 3–4 × 1020cm−3 and 2–3×1021cm−3, respectively. The room temperature mobility and resistivity of DyP are 300 cm2/Vsec and 60 μ Ω cm, respectively. The room temperature mobility of DyAs is about 50 cm2/Vsec. DyP forms a Schottky barrier to GaAs with a barrier height of 0.81eV and DyAs forms a weak Schottkyt barrier to GaAs. All relevant data will be presented along with schemes for using DyP and DyAs as potential interconnects to III-V compound semiconductors.
Organically Deposited Metallic Films for Device Fabrication
Authors: O'Keefe T. , Stroder M. , O'Keefe M. 
Published: April 2011

ABSTRACTAdvances in integrated circuit density, speed and complexity are dependent on lower resistance, finer line width on-chip interconnections. Methods for incorporating copper interconnects into IC fabrication processes have been developed which accomplish this objective but most of these methods use some form of blanket metal deposition that requires mechanical and/or chemical removal of excess material. To date, investigations into the selective deposition of conductor materials for device fabrication have met with limited success. A new process for selectively depositing metallic conductors using inexpensive, organic-based chemical solutions could potentially force a paradigm shift in the deposition of metals for microelectronic applications. Reversing the process currently used for selectively removing impurities from metal bearing waste streams, electrochemically controlled deposition of metals from electrically non-conducting organic solutions on submicron feature sizes is possible. A description of the fundamental electrochemical processes involved and parameter space available to engineer the solution chemistry will be presented along with experimental results from model systems. A discussion of the technology in light of ULSI issues and applications will be included.
Conducting Thin Films of Ruthenium Oxide Prepared by Mocvd
Authors: Hones P. , Kohli C.-H. , Sanjinés R. , Lévy F. , Gerfin T. , Grätzel M. 
Published: April 2011

ABSTRACTConducting thin films of RuO2 were grown at temperatures down to 623K on glass by metalorganic chemical vapor deposition (MOCVD). Tris-trifluoroacetylacetonate-ruthenium(III) (Ru(tfa)3) served as precursor. Smooth, specular and well adherent films were deposited, if the reaction gas contained water. The films were investigated by X-ray diffraction, SEM, and fourprobe resistivity measurement. Growth kinetics were also studied by in situ ellipsometry. The results are compared with films prepared by d.c. reactive sputtering before and after annealing. The properties of the MOCVD films, in particular the resistivity (ρ down to 72 μΩcm), are comparable to CVD films deposited at much higher temperatures and sputtered films after high temperature annealing.
Chemical Vapor Deposition of Tantalum Nitride Films Using Pentakis(Diethylamido)Tantalum and Ammonia
Authors: Cho Sung-Lae , Kim Ki-Bum , Min Seok-Hong , Shin Hyun-Kook 
Published: April 2011

ABSTRACTTantalum nitride (TaN) films were deposited by using pentakis(diethylamido)tantalum and ammonia. The activation energies of the surface reaction were obtained with the NH3 flow rate. In addition, the resistivity, composition, crystal structure, and microstructure were systematically studied with the NH3 flow rate from 0 to 25 sccm. The resistivity of the asdeposited film was decreased as the NH3 flow rate was increased, but it was increased at the NH3 flow rate of 25 sccm. The minimum value of resistivity is about 7000 μΩ-cm at the NH3 flow rate of 20 sccm. The carbon content in the film was decreased down to 1 at.% as the NH3 flow rate was increased up to 25 sccm by Auger electron spectroscopy. Rutherford backscattering spectrometry showed that the N/Ta ratio is about 1.75, which is not considerably changed with the NH3 flow rate. In spite of this high nitrogen content in the film, it was revealed that the fcc TaN was formed by x-ray diffractometry and transmission electron microscopy. The etch-pits test showed that 50-nm-thick TaN films deposited at the NH3 flow rate of 0 and 25 sccm prevented the diffusion of Cu into the Si substrate at the annealing condition of 500 °C and 550 °C for 1 hour, respectively. The step coverage was estimated as over 80 % at the NH3 flow rate of 0 sccm and below 10 % with the addition of NH3 in 0.5 μm × 1.5 μm contacts by cross-section scanning electron microscopy.
Copper Metallization Layers on Bismuth-Telluride Substrates: Effectiveness of Cr, Pt, and Ta40Si14 N46 Thin Films as Diffusion Barriers
Authors: Kacsich T. , Nicolet M.-A. , Kolawa E. , Fleurial J.-P. 
Published: April 2011

ABSTRACTFor power-chip cooling devices based on Bi2Te3 thick films, copper is a desirable choice as metallic conductor, because it has high thermal conductivity and low electrical resistivity. On the other hand, Cu shows donor activity in Bi2Te3, and is known for its high diffusivity in bismuth-telluride and the rapid formation of Cu2Te. Therefore, the deployment of a chemically inert, low resistivity diffusion barrier between the Cu metallization layer and the thermoelectric base material is indispensable. In this paper we report on the effectiveness of films of Cr, Pt, and Ta40Si14N46 as diffusion barriers at temperatures up to 350°C for Cu overlayers on Bi2Te3 bulk substrates. The films, each about 100 nm thick, were magnetron-deposited on the Bi2 Te3 followed by about 300 nm thick copper overlayers without breaking vacuum. The samples were annealed in vacuum at temperatures of 200 and 350°C for up to 50 h. The performance of the metals and the tantalum-silicon-nitride films as diffusion barriers for Cu inward and Bi and Te toward diffusion was evaluated by 2.0 MeV4 He backscattering spectrometer and x-ray diffraction. While the Cr and Pt films fail already after hours of annealing at 200°C, the Ta40Si14N46 film remains intact at this temperature after vacuum heat treatment for 50 h, and even at 350°C for 1 h as well. Ta-Si-N, and related ternary materials of this type, have already shown to be highly effective barriers in Cu/Si contacts. This study demonstrates that their field in application extends quite beyond Si-based technology.
Texture and Grain Boundary Structure Dependence of Hillock Formation in Thin Metal Films
Authors: Nowell Matithew M. , Field David P. 
Published: April 2011

AbstractThe development of hillocks on metal films during annealing is detrimental to downstream processing of integrated circuit structures. This work focuses upon the local character of texture and grain boundary structure near hillocks in metal films. It is apparent from the results that local grain boundary structure and texture strength are important parameters in identifying locations in the films that are preferentially susceptible to failure under given conditions. Results in aluminum and platinum films indicate that non-(111) oriented grains preferentially contain hillocks. In addition, (111) oriented grains with boundaries characterized by high angle rotations about random axes are prone to hillock formation.
Electromigration Failure Kinetics in Al Alloy Lines: A Microstructure-Based Constitutive Equation
Authors: Kang S. H. , Morris J. W. , Kim C.-U. 
Published: April 2011

AbstractIn previous work we proposed a simple constitutive equation that describes the electromigration failure kinetics in naturally passivated Al(Cu) quasi-bamboo lines. The time to failure, tf obeys the relation, tf = t0 exp (−l/t0), where t0 and l0 are characteristic constants and l is the length of the polygranular segment that causes failure (which is ordinarily the longest polygranular segment in the line). The present paper gathers the data supporting this relation, which includes tests on lines as-patterned and annealed at low and high temperature, and examines the dependence of the factors t0 and l0 on current density, test temperature, line geometry, and Al2Cu precipitate distribution. The experimental data suggest that to varies geometrically with j, with exponent n ≈ 2.8, and exponentially with T−1, with activation energy of ∼0.69 eV. It also varies with the line width and the distribution of Al2Cu precipitates. On the other hand, l0 is only weakly dependent on current density and temperature, but may vary with the ratio of line width to grain size (w/G).
Modelling of Heat Conduction and Thermal Stresses in Multilevel Interconnects
Authors: Shen Y. -L. 
Published: April 2011

AbstractThe effects of metal Joule heating in interconnects were studied numerically. Particular attention is devoted to the multilevel nature of interconnects in modem microelectronic devices. Heat conduction analyses were carried out to quantify the temperature rise in structures composed of various levels of metal lines under different electric current densities. Two types of metallization (aluminum and copper) and two types of interlevel dielectric (silicon dioxide and polyimide) were considered. It was found that increasing the total number of metal level and/or switching the dielectric from silicon dioxide to polymer-based low-k dielectrics can cause substantial temperature increases, pointing out that interconnect Joule heating can become a major reliability threat in future applications. Thermal stresses induced by the nonuniform temperature field were also analyzed.
Dependence of Stress-Related Reliability of Metallic Power Line on Physical Properties of Its Overlayer, Chip Location and Package Structure in Memory Devices
Authors: Lee Seong-Min 
Published: April 2011

AbstractThis work shows that shear failure in the metallic power line on the IC chip, which mainly takes place after plastic packaging, is always followed by mechanical damage in its overlayer. Thus, the topological feature of the metallic overlayer is important in defining shear damage in the metal line. On the other hand, since open failure in the metal line associated with stress migration is caused by tensile stress resulting from thermal mismatch with its overlayer, the physical properties of the overlayer plays an important role in determining open failure in the metal line. The FEM simulation shows how the tensile stress distribution along a metal line varies with the physical properties of its overlayer. The metallic overlayer with an initial coating of a ductile oxide layer was estimated to be a very effective way of minimizing tensile stress induced to the metal line. On the other side, shear damage of the metal line was found to be highly sensitive to the chip location or the package structure. The numerical calculation also indicates that shear stress applied to the passivated metal line, which reveals a maximum value at the chip comer, can be considerably reduced by chip premolding overcoating with ductile photosensitive polyimide.
Measuring Local Strain Variations Full-Field in Photoresist Thin Films Using Photolithographic Dot Arrays
Authors: Lin P.P. , Rowlands R. E. 
Published: April 2011

AbstractPhotoresist (such as PMMA) thin films are among the most important materials in semiconductor fabrication processes. Photolithography exclusively uses photoresist to construct the circuit pattern. The quality of a pattern relies on the uniformity of a photoresist layer. However, thermal expansion mismatch between the photoresist and silicon substrate during the subsequent thermal cycling process inevitably produces undesirable residual strains/stresses in the resist layer. Such residual fields can deteriorate the desired quality of the final pattern. A recently developed method is used here to record full-field strain information in the thin resist film.Traditional methods such as wafer curvature measurement or x-ray diffraction (for crystalline films) have not been effective for measuring the full-field strains. However, using a deposited dot array in the interface between the film and substrate, one can measure the strains in the thin film, full-field, by analyzing the displacements of individual dots. A biquadratic surface model is employed to fit these dot pattern displacements. An IDL (Interactive Data Language, Research Systems Inc.) program is utilized repeatedly to accurately locate the positions of the individual dots and transform that information into displacement and strain data by differentiating the biquadratic surface. This study successfully demonstrates a straightforward approach to determine the residual strains, full-field, in photoresist thin films.
Investigations of Electromigration Failure by Electrical Measurement and Scanning Probe Microscopy With Additional Simulation
Authors: Fabricius Alexander , Breternitz Volkmar , Knedlik Christian , Henning Andreas , Liebscher Eckhard , Vogel Silvia 
Published: April 2011

AbstractA set of 10, 5 and 2 µm wide, 500 µm long and 0.7 µm thick Al/Si/Cu-lines (1% Si, 0.5% Cu) was investigated under different stress conditions. Typical stress conditions were current densities of 2 to 6 MA/cm2and ambient temperatures of 125 to 225°C. For additional mathematical simulation it was important to observe the complete history of the resistance development from the beginning until the break down of the samples. Depending on the line width a number of different resistance developments and times to failure occured. Especially at smaller line widths, i. e. near to bamboo structures, the differences of the resistance development and times to failure are wide-ranging. This fact must be taken into acount for the simulation. Furthermore unpassivated samples were used to enable investigations of the structures by SEM and SPM. Measurements of the size of hillocks and voids has been carried out by AFM. Thereby twin-crystals were observed. This fact indicates that there are special strains, which could be estimated.Another aspect of investigations was the exact measurement of the temperature in the break down area. For that purpose a special test structure with diodes underneath the stressed line was developed. These diodes are used to deduce local temperatures.
Effect of Thermal Treatment on the Hardness and Fracture Toughness of Sputter Deposited Bi-Layered Thin Films on Silicon
Authors: Manoharan M. , Narayanan B. , Muralidharan G. 
Published: April 2011

AbstractMicrohardness testing is widely used for characterizing the mechanical properties of both bulk materials and thin films. Although this technique is usually associated with hardness measurements, fracture properties of brittle materials can also be studied with cracking associated with microhardness indentations. It is well known that the length of radial cracks emanating from the comers of indents made with Vickers and Berkovich indenters is related to the fracture toughness of the material. In the present study, microhardness testing has been used to follow the evolution of the mechanical properties of a 10 nm.Cu/200 nm. Ni(V)/300 nm. Al(Cu) thin film deposited on a Si substrate. Composite hardness and fracture toughness have been followed as a function of heat treatment temperatures and times and were found to be dependent on both variables. The roles of residual stresses, interdiffusion, and intermediate phase formation in the observed variation in hardness and fracture toughness are discussed.
Segregation of Cu on Etched and Non-Etched Al(Cu) Surface
Authors: Li Hua , Maex Karen , Brijs Bert , Conard Thierry , Vandervorst Wilfried , Baklanov Michael , Boullart Werner , Froyen Ludo 
Published: April 2011

AbstractIn this paper, we have studied the segregation phenomenon of Cu on the surfaces of patterned lines, dry-etched films and non-etched films, by using X-ray photoelectron spectroscopy and lower energy Rutherford Backscattering Spectrometry. Significant enrichment of Cu is found on the sidewall of the lines. Annealing at 350°C and above cause the disappearance of this enrichment. Origin and evolution of this Cu enrichment have been investigated on films taken out from different steps of the etching process. It has been found that most of the Cu products induced by the plasma etching are CuCl and CuCl2 and they are removed mostly from the top Al oxide layer by the strip process. On the interface area between Al and the native oxide, considerable quantities of etched induced Cu are retained. This Cu is identified to be mainly metallic Cu. Different from the mechanism explained above, thermal annealing can also cause Cu segregation. We have found that Cu atoms diffuse into the native Al oxide where they form Cu2O.
Multilayer Microelectromechanical Structures for Material Property Characterization
Authors: Pratt R. I. , Johnson G. C. 
Published: April 2011

AbstractA new class of micro-electro-mechanical systems (MEMS) for material characterization is presented. These multilayered structures are lateral resonators which allow the determination of material properties of the different materials making up the system. Of particular significance is the ability to characterize many new materials previously untestable by resonant techniques. The basic lateral resonant structures are made of a single material, usually doped polycrystalline silicon, with beams anchored to the substrate at one end and supporting a rigid mass at the other. The rigid mass has a comb-shaped region on each side for electrostatically actuating and sensing the motion. The use of this electrostatic comb drive requires that the structure be made of a material that is electrically conductive. Thus, the class of materials which is amenable to characterization by resonance techniques has been somewhat limited. Multilayer structures, tested in conjunction with these basic monolithic structures, permit properties of both the base material and the subsequent layers to be determined. Stiffness and mass density of many new materials can be obtained by comparing the behavior of multilayer structures with their single-layer counterparts. Experimental designs and the associated analytical techniques for obtaining various properties are presented.
Polysilicon Tensile Testing With Electrostatic Gripping
Authors: Sharpe W. N. , Turner K. , Edwards R. L. 
Published: April 2011

AbstractTechniques and procedures are described for tensile testing of polysilicon specimens that are 1.5 or 3.5 νm thick and have various widths and lengths. The specimens are fixed to the wafer at one end and have a large free end that can be gripped by electrostatic forces. This enables easy handling and testing and permits the deposition of 18 specimens on a one-centimeter square portion of a wafer. The displacement of the free end is monitored, which allows one to extract Young's modulus from the force-displacement record. Some of the wider specimens have two gold lines applied so that strain can be measured interferometrically directly on the specimen to record a stress-strain curve.The specimens were produced at the Microelectronics Center of North Carolina (MCNC). When compared with earlier results of wider MCNC specimens that were 3.5 μm thick, the Young's modulus is smaller and the strength is slightly larger.
The Effects of Texture and Doping on The Young's Modulus of Polysilicon
Authors: Lee Sangwoo , Cho Changho , Kim Jongpal , Park Sangjun , Yi Sangwoo , Kim Jongjun , Cho Dong-Il Dan 
Published: April 2011

AbstractPolysilicon films deposited by low pressure chemical deposition (LPCVD) are the most widely used structural material for microelectromechanical systems (MEMS). However, the structural properties of LPCVD polysilicon films are known to vary significantly, depending on deposition conditions as well as post-deposition processes. This paper investigates the effects of phosphorus doping and texture on Young's modulus of polysilicon films. Polysilicon films are depostied at 585°C, 605"C, and 625°C to a thickness of 2µm. Specimens with varying phosphorus doping levels are prepared by diffusion doping at various temperatures and times using both POCl3 and phosphorsilicate glass (PSG) as the source. Texture is measured using an X-ray diffractometer. Young's modulus is calculated by taking the average of the values calculated from the resonant frequencies of four-different size lateral resonators. Our results show that Young's modulus of diffusion doped polysilicon films decreases with increasing doping concentration, and increases with increasing <111> texture.
Finite Element Simulations of the Mechanical Stress in and Around Narrow Tisl2Lines
Authors: Steegen A. , De Wolf I. , Maex K. , Ignat M. 
Published: April 2011

AbstractThe primary objective of this work is to carry out a combined experimental and numerical investigation of the mechanical stress induced during the Ti-silicidation of narrow lines spaced by a Poly Buffered Local field oxide. Therefore micro-Raman spectroscopy (μRS) measurements of local mechanical stress are combined with simulations by Finite Element Modeling (FEM). Numerical determination of the local stress in the Si-substrate by means of FEM becomes more and more important when scaling down the device dimensions because the spatial resolution of μRS is limited at about 1μm and because the stress in the Si-substrate underneath silicided lines can not be detected using pRS unless the silicide is very thin. The Finite Element analysis was done using SYSTUS and involves a two dimensional plane strain thermo-elastic formulation. A good agreement was obtained between the FEM simulations and the μRS data for line widths above 1Bm making the extrapolation of the FEM to line widths smaller than I1m an attractive alternative for μRS.
Dopant Mapping and Strain Analysis in B Doped Silicon Structures Using Micro-Raman Spectroscopy
Authors: Bowden M. , Gardiner D. J. , Lourengo M. A. , Hedley J. , Wood D. , Burdess J. S. , Harris A. J. 
Published: April 2011

AbstractRaman microscopy, using a novel line focus configuration, has been used here to study boron concentration distributions and depth profiles in silicon for two different sources of dopant. Changes in the Raman phonon peak frequency for boron doped silicon have been calibrated against concentration by comparison with SIMS data and a relationship between Raman shift and lattice strain has been obtained.