bluuebunny/crossref_metadata_2025 huggingface dataset:
Deposition of Amorphous Carbon Films from Laser-Produced Plasmas
Authors: Marquardt C. L. , Williams R. T. , Nagel D. J.
Published: April 2011

Amorphous carbon films deposited by sputtering or ion-beam techniques, as well as a-C:H films produced by glow discharge in hydrocarbon vapor, can exhibit interesting and desirable properties such as hardness, wide optical gap, high resistivity and chemical inertness. A critical parameter common to all methods for producing such films appears to be kinetic energy of the ions or atoms incident on the growing film. We report an investigation of laser-produced carbon plasmas as a deposition source which can supply ions and atoms having energies requisite for the production of hard carbon films. The plasmas were generated by focusing 1.06 μm radiation from a Q-switched Nd:YAG laser onto a carbon rod which could be rotated within the vacuum chamber to present a fresh surface for each shot. Plasma temperature, varied as a function of laser pulse energy, was monitored by recording X-UV plasma emission spectra during deposition. Films having thicknesses up to ˜0.5 μm were deposited on various substrates and were evaluated by microscopic inspection, thickness profiling, optical transmission measurements and hardness testing. Hardness increased significantly with plasma temperature, from about 3 to over 7 on the Mohs scale. There was no corresponding increase in optical gap, which remained near 0.4 eV for all films.
Plasma Deposition of Amorphous Metal Alloys
Authors: Hays Auda K.
Published: April 2011

Rapid solidification, sputtering and electroless chemical deposition have been used to produce amorphous metal alloys which possess excellent corrosion and abrasion resistance. This paper discusses a new technique for obtaining amorphous metal alloy coatings. This technique consists of dissociating mixtures of organometallics (metal carbonyls) and metalloid hydrides in a hydrogen carrier gas using a radio-frequency discharge. In particular, the formation of Ni-P alloys is discussed.

Plasma decomposition of Ni(CO)4 and PH3 in argon and hydrogen carrier gases [Ni(CO) 4/PH3˜8/l] yielded films that were black and silver, respectively, in appearance. Both films were amorphous as determined by transmission electron microscopy. Films deposited using a hydroqen carrier gas were three orders of magnitude more conductive than those deposited using an argon carrier gas. Analysis of both films using electron microprohe analysis and inductively-coupled plasma spectroscony showed an enrichment of P in the films over the P content in the plasma qas mixtures. Reducinq the P content of the plasma gas mixture [Ni(CO)4/PH3˜17/Il yielded crystalline films with no P enrichment. The grain size in these films was ˜Å as determined by x-ray line-broadeninq.

Using Auger electron spectroscopy, films deposited using hydroqen and argon carrier gases were determined to have, in addition to Ni and P, small amounts of carbon (8–12 at%) and oxygen (1–4 at%). Infrared spectra of both crystalline and amorphous films showed chemisorhed CO.
Amorphous Polyphosphide Thin Films Prepared by Sputtering
Authors: Schachter Rozalie , Viscogliosi Marcello
Published: April 2011

A sputtering method to prepare amorphous polyphosphide thin films has been investigated. The method consists of sputtering from a polyphosphide (KP15) target and plasma cracking of a P4 vapor stream injected into the plasma from an external phosphorus source. From the deposition rates of KP15 thin films, we determine that the plasma cracking efficiency of the P4 molecule into reactive P species required for compound growth is significantly higher than thermal cracking efficiency. We conclude that this method is applicable to other compound semiconductors (InP) and that the P4 delivery system used here should be useful in other techniques such as MBE or OMCVD
Evolutionary Growth Development in SiC Sputtered Films
Authors: Roy R. A. , Messier R.
Published: April 2011

The growth of rf-sputtered silicon carbide thin films has been studied over a wide range of substrate temperatures, producing films with crystal structures from completely amorphous to highly crystalline. The initial 100nm of growth is characterized by ‘void network’ type physical structure throughout the temperature regime studied. This network of polyhedra outlines the dominant physical structure features at the top surface of the film and is shown to grow in average lateral dimension (D) with increasing film thickness (t) as a parabola (D=K·tx). The growth exponent (x) describes the lateral growth rate of these parabolic growth cone columns and decreases with increasing film temperature, bombardment, and hydrogen in the plasma. In the highly crystalline films the lateral crystallite growth rate eventually exceeds the growth of void network columns present in 10–100nm films, producing abrubt increases in size of physical features between 100–1000nm levels. The results show that the evolutionary structure zone model consistently accounts for film growth behavior in the amorphous regime but must be modified for crystalline films.
Ion Bombardment Effect on the Properties of a-Si:H
Authors: Drevillon B. , Schmitt J. P. M.
Published: April 2011

In a low pressure multipole plasma, the energy of the charged species impinging on the substrate can be varied electrostatically. Spectroscopic ellipsometry is used to study the film growth and the surface morphology. Hydrogen evolution is used to investigate the release of hydrogen from the amorphous network. Moderate energy ion bombardment (Eion ‰ 50 eV) is shown to favour the formation of homogeneous high density films with a sharp interface. Weak ion bombardment (Eion ‰ 20 eV) results in a microscopically rough surface. The material strucbural variations are evidenced by hydrogen evolution kinetics.
Low Temperature Plasma Anodization of Silicides
Authors: Perriere J. , Siejka J. , Laurent A. , Enard J. P. , D'heurle F.
Published: April 2011

In the first time, hundreds nm thick oxide layers were formed by room temperature plasma anodization of some refractory disilicides. Nuclear microanalysis and Rutherford backscattering techniques were used to study the anodic oxidation of various metal silicides (Hf, Ti and Zr) in a multipolar oxygen plasma set-up. We have found that the low temperature (<100 °C) plasma anodization kinetics of Hf or Zr silicides is two orders of magnitude higher than that of Ti silicide although their thermodynamic and physicochemical behaviour are very similar. 200 nm thick Hf (or Zr) and Si mixed oxide layers have been obtained in one hour plasma anodization. Analysis of RBS spectra indicates that the ratio of Si to metal cation concentration in the bulk of oxide grownis the same than the silicide (HfSi2 or ZrSi2), while in the near surface region of oxide (20 to 30 nm) there is an enrichment in metallic oxide leading to a Si to Hf (or Zr) concentration ratio equal to unity. The spectacular difference between the anodization rates in oxygen plasma of Hf (and Zr) silicides comparing to Ti silicides can be related to the catalytic effect on plasma anodization of the Hf and Zr oxides.
Thermal Nitridation of Silicon in Nitrogen Plasma and Nitrogen-Hydrogen Plasma
Authors: Matsumoto S. , Nakamura H. , Eguchi S. , Fujita S. , Sasaki A.
Published: April 2011

Thermal nitridation of silicon in both nitrogen and nitrogen-hydrogen plasma has been performed around 1000°C for 5 min to 10 hr. From Auger electron spectroscopy analysis, the formed films contain some oxygen and are identified as oxynitride films in both cases. In nitrogen-hydrogen plasma, high nitrogen fraction( 0.8) in the film is obtained for the nitridation of 5 min. Thus, the addition of hydrogen to nitrogen enhances the nitrgen fraction in the film for such a short nitridation time. The film thickness is almost constant against the nitridation time and is limited to be about 40 Å. Capacitance-voltage characteristics of aluminum gate metal- nitride-semiconductor capacitors show stable behaviors and the fixed charge density at the film-substrate interface is estimated to be the order of 1012 cm−2 in both cases.
Application of Plasma Anodization Technique to Device Fabrication
Authors: Sugano Takuo
Published: April 2011

Applications of plasma anodization technique to Si, GaAs and InP dev-ices fabrication, demonstrated by the author's group, are reviewed. The feature of the technique is an electric field enhanced low temperature oxidation process. Suppression of the generation of oxidation induced stacking faults, the redistribution of impurities in the substrates and the bird's beak formation in selective oxidation process is an advantage in silicon technology. It must be stressed that plasma anodization is only one technique which has been proved to be successful in growing native oxide films on InP substrates for MISFETs fabrication.
Plasma Passivation Scheme for III–V Compound Semiconductor Surfaces
Authors: Theeten J. B. , Gourrier S. , Friedel P. , Taillepied M. , Arnoult D. , Benarroche D.
Published: April 2011

Passivation of III-V compounds, especially GaAs, is still a major problem. Surface mechanisms related to stoichiometry defects (free As formation, vacancies) play an important role in the detrimental effects observed on GaAs devices (interface traps, leakage currents, parasitic transients …).

We first analyze the phenomena occuring at GaAs (100) surfaces exposed to several (H2,N2 ) multipolar plasmas, with the following methods : - in situ study of the surface morphology and roughness using ellipsometry and electron diffraction - chemical analysis using photoemission and Auger spectroscopy - electrical analysis in situ (Fermi level position deduced from photoemission, work function measurements) or ex situ (device characterization, C(V) analysis).

Using H2 based plasma treatments, a complete cleaning (oxide and contamination removal) can be obtained at moderate (below 200 °C) temperatures. This process, associated with surface nitridation and dielectric deposition, yield improved surface properties (lower recombination velocity and reduction of devices parasitic effects).

The case of Ga1−xInxAs (100) surfaces (with x varying from 0 to 0.53)is then discussed and a comparative study is given, indicating that native nitridation may also be a good solution,in this case.
Time Resolved Diagnostics of RF Plasmas: a Fluid Model for ion Concentrations in the Sheath
Authors: Gottscho Richard A.
Published: April 2011

A one-dimensional fluid model is presented for time-dependent ion concentrations in chlorine containing discharges. The ion formation rate is determined from experimental plasma-induced emission intensities. The local field is estimated from spectrally resolved laser-induced fluorescence data obtained in similar, BCl3 discharges. Quantitative agreement with experiment is obtained implying that the basic assumptions in the model are valid: (1) ground state ions in the sheath are formed predominantly by electron-impact ionization; (2) Cl2+ ion motion is mobilitylimited by charge exchange collisions with Cl2 neutrals; (3) the degree of Cl2 dissociation is ∼. 65% at a power density of 1.8 W cm−3; (4) the ion concentration near the electrode is spatially uniform throughout most of the rf cycle; and (5) there are two times during a low frequency rf cycle when ions experience a strong extraction force.

Semi-empirical models like the one described here should be useful in computational optimization of plasma processes such as etching and deposition, which are in wicre-spread use throughout the microelectronics industry.
Effects of Gallium Arsenide Passivation on Scanning Tunneling Microscope Excited Luminescence
Authors: Reuter E. E. , Gu S. Q. , Bohn P. W. , Dorsten J. F. , Abeln G. C. , Lyding J. W. , Bishop S. G.
Published: April 2011

An ambient scanning tunneling microscope (STM) was used to excite luminescence in ptype epitaxial GaAs with four separate surface preparations: bare GaAs, Au layer, sulfurmonochloride layer, and one monolayer of octa-decyl-thiol. The STM with tungsten tip was operated at a constant tunnel current of 5 nA during a +1 V bias applied to the sample and the resulting tip to sample distance was fixed during a higher voltage bias pulse which excited luminescence. The luminescence intensity increased rapidly with increasing bias voltage for all passivation types with the octa-decyl-thiol passivation achieving the highest STM excited luminescence (STMEL) of 3500 photons/sec at 4 V bias. Above about 4 V the luminescence from the octa-decyl-thiol and sulfur-monochloride passivated samples fell off irreversibly, indicating that the sample surface had been modified. The Au passivated and unpassivated samples showed no such luminescence drop up to 4.8 V, the highest bias employed. Photoluminescence (PL) studies of the samples showed that PL intensities exhibited a weaker dependence upon passivation type than did STMEL intensities, a result consistent with the assertion that STMEL is more sensitive to the surface properties of the sample than is PL.
Direct Nanoscale Patterning by Atomic Manipulation
Authors: Salling Craig T.
Published: April 2011

The ability to create atomic-scale structures with the scanning tunneling microscope (STM) plays an important role in the development of a future nanoscale technology. I briefly review the various modes of STM-based fabrication and atomic manipulation. I focus on using a UHV-STM to directly pattern the Si(001) surface by atomic manipulation at room temperature. By carefully adjusting the tip morphology and pulse voltage, a single atomic layer can be removed from the sample surface to define features one atom deep. Segments of individual dimer rows can be removed to create structures with atomically straight edges and with lateral features as small as one dimer wide. Trenches ∼3 nm wide and 2–3 atomic layers deep can be created with less stringent control of patterning parameters. Direct patterning provides a straightforward route to the fabrication of nanoscale test structures under UHV conditions of cleanliness.
Molecular Beam Epitaxy Of Si/ZnS/Si(100) Heterostructures For Silicon-Based Quantum Devices
Authors: Zhou Xiaochuan , Li Feng , Spencer Gregory F. , Kirk Wiley P.
Published: April 2011

Special methods were developed to grow Si/ZnS/Si heterostructures for the purpose of developing silicon-based quantum devices. An arsenic passivation technique was used on silicon surfaces for the growth of ZnS. The effectiveness of this surface passivation was demonstrated by the improved crystal quality and decreased heterostructural interface-state density. A two-step growth method was developed for the epitaxial growth of silicon on ZnS surfaces. In this method the normal silicon epitaxial growth was preceded by a solid phase epitaxy process. Single crystal films of silicon were successfully grown on ZnS surfaces. Our discussion addresses two key issues: crystal defects and the density of interface states. The results of RHEED (reflection high energy electron diffraction), C-V (capacitance voltage), and SIMS (secondary ion mass spectroscopy) measurements are presented.
Nanoscale Features Grown by MBE on Nonplanar Patterned Si Substrates
Authors: Hobart Karl D. , Kub Fritz J. , Gray Henry F. , Twigg Mark E. , Park Doewon , Thompson Phillip E.
Published: April 2011

Si growth by molecular beam epitaxy on nonplanar patterned Si substrates is studied as a function of growth parameters. The substrates consist of a truncated pyramid template with {111} sides and (100) tops formed by anisotropic etching of Si(100). For growth temperatures ≤ 550°C no qualitative changes in the morphology of the template are observed. At growth temperatures between 650–700°C {113} facets begin to form on the (100) surface and reduce the lateral dimensions of the (100) facet to < 20 nm. At high temperatures (∼800°C) {113} facets remain stable and {111} facets no longer exist. The small (100) mesa formed at medium temperatures by facet reduction is exploited through the growth of Si/Si 1-xGex multiple quantum wells leading to low-dimensional structures. Observations are quantified by scanning electron and transmission electron microscopies.
Low-Dielectric Constant Film Formation By Plasma Fluorination Of Hydrocarbon Polymers
Authors: Kudo Hiroshi , Shinohara Rika , Yamada Masao
Published: April 2011

We have investigated plasma fluorination of hydrocarbon polymer films spincoated onto silicon wafers. Fluorinated hydrocarbon polymers gave low dielectric constants of 2.0 – 2.4 which was close to that of PTFE. However, the thermal stability of these fluorinated polymers inferior to that of the non-fluorinated polymers. We believe that this is due to a decrease in the molecular weight resulting from C-C bond cleavage. We think that such a side reaction will be controlled by removing residual oxygen in a fluorination chamber. The molecular structures of the fluorinated polymers were analyzed by X-ray photo emission spectroscopy. Finally, we proposed direct patterning of interlayer dielectrics using plasma fluorination.
Thermal And Mechanical Properties Of Low K Polymers
Authors: Chiang Chien , Mack Anne S. , Pan Chuanbin , Ling Yui-Lin , Fraser David B.
Published: April 2011

Low dielectric constant polymers offer many advantages in circuit performance, such as power dissipation, crosstalk and RC delay, when used as inter-layer dielectrics (ILDs). Silicon dioxide, a material commonly used as an ILD has a dielectric constant of 4.0. Organic polymers that have dielectric constant values ranging from 2.0 to 3.0 offer attractive alternatives to SiO2. However, it has been a great challenge to find organic polymers with thermal stability up to 450 °C. We have characterized thermal properties of polymers using thermal desorption analysis. isothermal TGA and FTIR to identify weak functional groups. In addition, we have measured the hardnesses and moduli of these polymers and found that the values are much lower than those of SiO2.Stress distributions in the interconnect system were analyzed using finite element modeling in order to understand potential reliability problems.
Thermal And Mechanical Properties Of Polyimide Films
Authors: Chen S. T.
Published: April 2011

In recent years, polyimide film has become a commonly used insulator for microelectronic devices including advanced semiconductor chip and high density packaging. It has the advantages of low dielectric constant, thermal stability and low processing cost. In general, it is important to understand both the thermal and mechanical properties of a microelectronic material. Thermal and mechanical properties play very important roles in terms of determining the device structural integrity. Mismatch of material properties could cause feasibility and reliability problems. These properties are also essential for mechanical stress and thermal stress modeling studies. Biphenyldianhydride-Phenylenediamine (BPDA-PDA) and Pyromellitic Dianhydride-Oxydianiline (PMDA-ODA) are two commonly used polyimide films in electronic industry. Their thermal expansion coefficients and mechanical properties were studied and reported here.
Fluorinated, Low Thermal Expansion Coefficient Polyimides For Interlayer Dielectric Application: Thermal Stability, Refractive Index And High Temperature Modulus Measurements
Authors: Auman Brian C.
Published: April 2011

The mechanical, thermal, electrical and moisture absorption properties of rod-like, fluorinated polyimides and copolyimides developed in our laboratory are briefly reviewed. Further characterization work on the most promising candidates for interlayer dielectric applications is reported. This includes in- and out-of-plane refractive index measurements to estimate the isotropy of the dielectric constant, isothermal TGA measurements to assess thermal stability at processing temperatures and dynamic-mechanical analysis to ascertain the glass transition temperature and the mechanical modulus at temperatures in excess of the glass transition
Preparation Of Low-Density Xerogels At Ambient Pressure For Low K Dielectrics
Authors: Smith D. M. , Anderson J. , Cho C. C. , Johnston G. P. , Jeng S. P.
Published: April 2011

Low density silica xerogels have many properties which suggest their use as a low dielectric constant material. Recent process improvements to control capillary pressure and strength by employing aging and pore chemistry modification, such that shrinkage is minimal during ambient pressure drying, have eliminated the need for supercritical drying. Although xerogels offer advantages for intermetal dielectric (IMD) applications because of their low dielectric constant (<2), high temperature limit, and compatibility with existing microelectronics precursors and processes, they suffer from unanswered questions. These include: 1) are all pores smaller than microelectronics features, 2) what are their mechanical properties (for processing and particle generation), and 3) what is their thermal stability. We have produced bulk xerogels under similar conditions to those used for films and studied the effect of density on the pore size distribution and bulk modulus.
Evaluation Of Amorphous Diamond-Like Carbon And Boron Nitride Films As Low Permittivity Dielectrics
Authors: Sullivan J. P. , Friedmann T. A. , Apblett C. A. , Siegal M. P. , Missert N. , Lovejoy M. L. , Mirkarimi P. B. , McCarty K. F.
Published: April 2011

Although films of diamond-like carbon (DLC) and hexagonal boron nitride (h-BN) have shown low dielectric constants in the range of 3 to 4, these materials have been unsuitable for use as interconnect dielectrics due to poor thermal stability and environmental degradation. These deficiencies can be addressed by depositing DLC films free of hydrogen (a-tC) and depositing the cubic phase of BN (c-BN). The dielectric characteristics of hydrogen-free DLC and c-BN that have been deposited by pulsed-laser deposition (PLD) have been evaluated using metal-insulator-metal and metal-insulator-semiconductor structures. For comparison, the dielectric characteristics of h-BN deposited by electron cyclotron resonance (ECR) were also evaluated. Despite the superior thermal and environmental stability of the a-tC and c-BN films and the attractively low deposition thermal budget (room temperature deposition for a-tC films, 400°C for c-BN films), the films exhibit dielectric constants comparable to those of bulk diamond and bulk BN, ∼ 6. Furthermore, the a-tC and c-BN films exhibit high compressive stress in the GPa range which limits their usefulness only to those applications requiring a thin dielectric layer, e.g. diffusion barriers or encapsulants.
Elastic Properties of Pure and Hydrogenated Ce/Fe Multilayer Films
Authors: Hassdorf R. , Arend M. , Felsch W.
Published: April 2011

The study of the elastic properties of pure Ce/Fe multilayers throughout the structural phase transition of the Fe layers from crystalline to amorphous reveals striking similarities to the crystal-to-glass transition in bulk metallic materials which is driven by a shear instability of the crystal lattice. The transition is reflected in a pronounced minimum (∼ –70%) of the flexural modulus of the multilayers as determined by a vibrating-reed technique. Hydrogenation leads to multilayers composed of CeH∼2/Fe, with distinctly different moduli depending on the texture of the Fe sublayers. For multilayers with a Fe (111) texture a reorientation transition of the spontaneous magnetization is observed at a well-defined temperature. This transition is accompanied by a relaxation of thermal stresses and a considerable softening (∼30%) of the flexural modulus.
An in Situ High Voltage Electron Microscopy Technique for the Study of Deformation and Fracture: in Multilayered Materials
Authors: Wall M.A. , Barbee T.W. , Weihs T.P.
Published: April 2011

A novel, in situ, high voltage electron microcopy technique for the direct observation of the micromechanisms of tensile deformation and fracture in nanostructured materials is detailed. This technique is particularly well suited for the dynamic observations of deformation and fracture in multilayered materials. The success of this type of in situ technique is highly dependent upon unique specimen preparation procedures and sample design, the importance thereof will be discussed. The initial observations discussed here are expected to aid in our understanding of the mechanical behavior of this new class of atomically engineered materials.
Reactive Phase Formation in Sputter-Deposited Ni/Al Thin Films
Authors: Barmak K. , Michaelsen C. , Bormann R. , Lucadamo G.
Published: April 2011

We have investigated reactive phase formation in magnetron sputter-deposited Ni/Al multilayer thin films with a 3:1 molar ratio and periodicities ranging from 2.5-320 nm. In addition, we studied the transformation of a codeposited film of the same composition. We find that an amorphous phase has already formed during deposition, and that the extentof formation of this phase increases with decreasing periodicity. The first crystalline phase then nucleates from this amorphous phase upon annealing. The formation of the amorphous phase considerably reduces the driving force and explains why during subsequent reactions nucleation kinetics become important. We obtain Ni2Al9 as the first product phase during heat treatment in some cases before NiAl3 occurs. For films with modulation periods larger than 40 nm, formation of NiAI3 is a two stage process as reported earlier, with the first stage being due to nucleation and growth to coalescence of NiAl3 grains, and the second stage being the growth of NiA13 normal to the initial interface until the reactant phases are consumed.
Specular and Off-Specular X-Ray Scattering as Quantitative Structural Probes of Multilayers. Application to MN/IR(111) Superlattices
Authors: Fischer H.M. , Fischer H.E. , Bessiere M. , Bobo J.-F. , Lenoble O. , Andrieu S. , Piecuch M.
Published: April 2011

Diffuse scattering of X rays is a particularly useful tool for studying interface and surface defects in single layer films. We have extended this technique to the study of multilayers. The samples are Mn/Ir(111) superlattices where Mn is pseudomorphic to Ir. We have studied three typical samples prepared at different substrate temperatures. Using theoretical analyses and simulations of both specular and off-specular X-ray scattering data at small angles as well as large angles, we show that large length-scale interfacial roughness is mainly due to the formation of terraces during growth at low deposition temperature, whereas small length-scale interfacial roughness occurs preferably at high deposition temperature and is mainly due to an atomic interdiffusion (i.e. the formation of an interface alloy) which manages to maintain a high degree of crystallographic order.
Pulsed Laser Deposition of Laterally Graded X-Ray Optical Multilayers on Substrates of Technical Relevance
Authors: Dietsch R. , Holz TH. , Krawietz R. , Mai H. , SchÖneich B. , Scholz R. , VÖllmar S. , Wehner B.
Published: April 2011

Pulsed Laser Deposition (PLD) is used for the preparation of Ni/C, W/C, and Mo/Si multilayers having X-ray optical quality. For the synthesis of layer stacks involving a uniform or a graded thickness distribution across 4"-wafers the conventional thin film deposition equipment of PLD has been modified. This modification provides a precise spatial control of the plasma plume orientation in the deposition chamber. With this arrangement the emission characteristic of the plasma source can be computer controlled and the desired coating profile can be tailored across an extended substrate via a stepper-motor-driven target manipulator.

Thus film thickness uniformity (δts < 2%) is obtained on substrates up to 4" diameter even for smaller target-substrate distances. For laterally graded Ni and C individual layers linear thickness gradients of dts/dx = 3.2 × 10−8 were confirmed over the total substrate length by spectroscopic ellipsometry. The parameters deduced from single layer deposition were applied for the synthesis of laterally graded Ni/C multilayers. A mean value of the gradient of the stack period thickness dt/dx = 6.2 × 10−8 confirmed by X-ray reflectometry (nominal value: dt0 /dx = 6.4×10−8 ) characterizes precision and reproducibility of the coating process.
Capacitance Humidity Sensor
Authors: Ralston Andrew R.K. , Thoma Paul E. , Klein Carl F. , Denton Denice D.
Published: April 2011

A capacitance relative humidity (RH) sensor is described that has a design, construction, and material composition that result in an inexpensive and robust sensor. This sensor has a multilayer, free-standing film construction. It consists of a humidity sensitive polyimide (PI) dielectric core and conductive layers consisting of carbon filled polysulfone on each side of the polyirnide film to form a capacitor. The polyimide used is a BPDA-ODA type, and replaces a PMDA-ODA type polyimide used in a previous version of this sensor. The BPDA-ODA sensor has a nominal capacitance of 200 pF and a nominal sensitivity of 13% at 100% RH. The characteristics of this humidity sensor are discussed and compared to the characteristics of the PMDA-ODA type sensor. Characteristics considered include the PI film moisture uptake and water vapor transmission, and the sensors' sensitivity to relative humidity, frequency response, and aging at 85°C/85% RH. The dual-state sorption model and free volume calculations are used to demonstrate that observed differences in the film are due to differences in chemical composition between the films.
Multilayer Precursor Synthesis of New Copper-Tungsten Selenides
Authors: Fister Loreli , Hornbostel Marc D. , Johnson David C.
Published: April 2011

We have made new ternary compounds in the copper tungsten selenium system using multilayer thin films as reactants. The compounds appear to be unstable above temperatures near 1000ºC with respect to binary compounds, which helps to explain the difficulty in making these compounds by conventional methods.
High Quality NiFe/Ag Superlattices Made by Pulsed Laser Deposition (PLD)
Authors: Treece Randolph E. , Dorsey Paul , Horwitz James S. , Qadri Syed , Chrisey Douglas B.
Published: April 2011

High-quality thin-film superlattices of permalloy (NiFe) and silver (Ag) have been grown by pulsed laser deposition (PLD) for the first time. The alternating metallic layers weregrown from individual NiFe and Ag targets utilizing an automated multi-target holder coupled to a conventional PLD system. The targets were ablated at a base pressure of 4×10−7 Torr and the material deposited on room-temperature (100) silicon and on fused silica substrates. The films were characterized by X-ray diffraction (XRD), magnetic field-dependent resistivity, and ferromagnetic resonance (FMR). XRD was used to confirm uniform bilayer thicknesses. The magnetic field-dependent resistance measurements indicated the presence of magnetoresistance in the deposited films. An as-deposited film with a bilayer thickness of 75 Å demonstrated a roomtemperature magnetoresistive effect of 0.15 %. FMR has been used to determine the relationship between NiFe magnetism and the observed magnetoresistance.
Microhardness, Structure, and Composition Study of Amorphous Hydrogenated Boron Carbide
Authors: Lin Shu-Han , Li Dong , Feldman Bernard J.
Published: April 2011

We have grown amorphous hydrogenated boron carbide thin films by rf plasma decomposition of diborane and methane. The chemical composition, infrared absorption, optical absorption, and microhardness of these thin films were measured. As a function of increasing diborane concentration in the feedstock, we observe increasing boron and hydrogen concentrations, increasing infrared absorption at 1330 cm−1 due to boron icosahedra, increasing optical bandgaps, and an unchanging microhardness in the grown films. The microhardness should have decreased due to the increasing hydrogen concentration; this expected decrease may have been balanced by an increased microhardness due to the boron icosahedra.
Stress in Thin Diamond Films on Various Materials Measured by Microraman Spectroscopy
Authors: Ralchenko V. G. , Obraztsova E. D. , Korotushenko K. G. , Smolin A. A. , Pimenov S. M. , Pereverzev V. G.
Published: April 2011

MicroRaman spectroscopy has been used to determine residual stress in polycrystalline diamond films grown by CVD process in a DC arc plasma from CH4/H2 gas mixtures. A variety of substrate materials, including silica glass, Si, SiC, Mo, Cu, Ni, Fe-Ni alloy, WC-Co and steel, were selected in order to extend as much as possible the range of the substrate thermal expansion coefficients (CTE). Diamond adhesion to catalytically active materials (Ni, Fe, Co) and Cu was improved with a thin buffer layer of CVD tungsten. The observed Raman peak shifts were converted to stress values σmeas in the framework of biaxial stress model. Compressive stress has been found in diamond films at all substrates, except SiO2, which provided a tensile stress up to +2.3 GPa. The maximum compressive stress has been detected for Ni substrate σmeas =-11.4 GPa at room temperature and σmeas =-14.3 GPa at T=78 K. A linear dependence of stress on temperature was found at Ni in the temperature range 78–520 K, in good agreement with prediction of thermal stress model. The splitting of diamond peak to singlet and doublet becomes observable at σ>8–9 GPa. The measured stress correlates in general with calculated thermal stress, increasing with CTE value of respective substrate materials, copper being the only exclusion because of its high plasticity.
Adhesion and Young's Modulus of CVD Diamond Thin Films Grown Over Various Substrates
Authors: Ramesham R. , Askew R. F. , Rose M. F.
Published: April 2011

Diamond films were deposited by microwave plasma CVD using H2 and CH4 gas mixture over various substrate materials such as Si, Pd, Be, Cu, Mo, AIN, SiO2, Si3N4, Al2O3, Sapphire, Quartz, Ni-base alloys, single crystal Ni, boron nitride, and Ti. We have used a Z-axis pull stud test to determine adhesion strength of diamond film to some of the substrates. Our observations on the adhesion of diamond films to the above substrates are reported. A method will be described to evaluate Young's modulus of CVD diamond films using fabricated diamond cantilever beams.
Diamond {111} Surface: Graphitization or Reconstruction?
Authors: Jungnickel G. , Porezag D. , Frauenheim Th. , Lambrecht W. R. L. , Segall B. , Angust J. C.
Published: April 2011

The reconstruction of the diamond {1111} surface is re-examined by means of density functional theory based tight-binding molecular dynamics. Evidence is found for competition between a graphitizing tendency leading to an unreconstructed but relaxed 1 × 1 surface and a π-bonded chain-like 2 × 1 reconstruction. The implications of the possible co-existence of these two distinct surface phases for diamond growth are discussed.
Diamond-Like Carbon Films for Silicon Passivation in Microelectromechanical Devices
Authors: Houston M. R. , Howe R. T. , Komvopoulos K , Maboudian R.
Published: April 2011

The surface properties of diamond-like carbon (DLC) films deposited by a vacuum arc technique on smooth silicon wafers are presented with specific emphasis given to stiction reduction in microelectromechanical systems (MEMS). The low deposition temperatures afforded by the vacuum arc technique should allow for easy integration of the DLC films into the current fabrication process of typical surface micromachines by means of a standard lift-off processing technique. Using X-ray photoelectron spectroscopy (XPS), contact angle analysis, and atomic force microscopy (AFM), the surface chemistry, microroughness, hydrophobicity, and adhesion forces of DLC-coated Si(100) surfaces were measured and correlated to the measured water contact angles. DLC films were found to be extremely smooth and possess a water contact angle of 87°, which roughly corresponds to a surface energy of 22 mJ/m2. It is shown that the pull-off forces measured by AFM correlate well with the predicted capillary forces. Pull-off forces are reduced on DLC surfaces by about a factor of five compared to 10 nN pull-off forces measured on the RCA-cleaned silicon surfaces. In the absence of meniscus forces, the overall adhesion force is expected to decrease by over an order of magnitude to the van der Waals attractive force present between two DLC-coated surfaces- To further improve the surface properties of DLC, films were exposed to a fluorine plasma which increased the contact angle to 99° and lowered the pull-off force by approximately 20% over that obtained with as-deposited DLC. The significance of these results is discussed with respect to stiction reduction in micromachines.
Mechanical Properties of Amorphous Hard Carbon Films Prepared by Cathodic ARC Deposition
Authors: Anders Simone , Anders André , Ager Joel W. , Wang Zhi , Pharr George M. , Tsui Ting Y. , Brown Ian G. , Bhatia C. Singh
Published: April 2011

Cathodic arc deposition combined with macroparticle filtering of the plasma is an efficient and versatile method for the deposition of amorphous hard carbon films of high quality. The film properties can be tailored over a broad range by varying the energy of the carbon ions incident upon the substrate and upon the growing film by applying a pulsed bias technique. By varying the bias voltage during the deposition process specific properties of the interface, bulk film and top surface layer can be obtained. We report on nanoindentation and transmission electron microscopy studies as well as stress measurements of cathodic-arc amorphous hard carbon films deposited with varied bias voltage. The investigations were performed on multilayers consisting of alternating hard and soft amorphous carbon.
A Comparative Study of Residual Stresses and Microstructure in a-tC Films
Authors: Martínez-Miranda L. J. , Sullivan J. P. , Friedmann T. A. , Siegal M. P. , Mercer T. W. , Dinardo N. J.
Published: April 2011

We compare the microstructure of highly tetrahedrally-coordinated-amorphous carbon (atC) films prepared by pulsed laser deposition (PLD), measured using both small angle x-ray scattering (SAXS) and x-ray reflectivity, with other physical properties such as film stress and electrical resistivity. These properties are controlled by the film growth conditions and film thicknesses. Films prepared under vacuum conditions exhibit a shift in the measured mass density, as a function of laser energy density. The density for films approximately 600Å thick approach that of crystalline diamond. The measured densities for thicker, approximately 1000Å films, exhibit a smaller shift, and a lower density value. This shift correlates to observed changes in film stress and electrical resistivity. The small angle signal of the reflectivity spectra suggests the presence of layering, or in-plane density variations or a combination of both within the films.
The Effect of Temperature on the Deformation of Diamond Surfaces
Authors: Brookes Chris A. , Brookes E. J. , Xing G.
Published: April 2011

A brief review is given of recently published work on the fracture and plastic flow of natural and synthetic diamond crystals when deformed by softer impressors at elevated temperatures. Under these conditions, a brittle-ductile transition (BDT) temperature for the different types of diamond has been established.

In this paper we show that below the BDT temperature, brittle ‘chatter’ cracking on {111} cleavage planes accounts for anisotropic wear provided that the mean contact pressure exceeds about 10 GPa. Above the BDT temperature, titanium diboride sliders develop contact pressures sufficient to cause extensive plastic deformation of the diamond specimens but insufficient to produce cleavage fracture. However, repeated sliding with TiB2 does lead to cumulative plastic flow preceding fatigue type fracture on {110} planes. Using cubic boron nitride and diamond sliders above the BD T temperature leads to a combination of both plastic deformation and {110} cracking. The coefficient offriction is a maximum in <100> and a minimum in <110> directions. and the measured scratch hardness, which confirms that the <100> directions are softer than <110>, is shown to be consistent with the predictions of a resolved shear stress model which was de velopedffor explaining anisotropy in all crystals.
1D and 2D Monte Carlo Simulations of Pulsed Laser Ablation Of Si/Ga Into Ar/O2With A Substrate
Authors: Capewell D. L. , Goodwin D. G.
Published: April 2011

The Direct Simulation Monte Carlo (DSMC) method is applied to the problem of pulsed laser deposition in both 1D and 2D axisymmetric simulations. A source of target atoms expands into a cylindrical volume containing a background gas at room temperature and pressures up to 100 mTorr in the presence of a diffusely reflecting substrate. At regular intervals, the density and temperature of each species are computed. Particle flux and energy per particle incident on the substrate are also monitored as functions of time. The simulation results qualitatively compare well with experimental plume diagnostics, with measured film growth rates as a function of background gas pressure, and with measured changes in film growth stoichiometry resulting from the introduction of a background gas into a two-component PLD system.
High Quality RTCVD Sidewall Spacer Dielectrics
Authors: Miles D. S. , Mirabedini M. R. , Venables D. , Wortman J. J. , Maher D. M.
Published: April 2011

Rapid thermal chemical vapor deposition (RTCVD) has been investigated as an alternative to low pressure chemical vapor deposition (LPCVD) for formation of sidewall spacer dielectric. Silane (SiH 4 ) and tetraethylorthosilicate (TEOS) were chosen as the silicon gas sources in these studies. Reasonable deposition rates were obtained for RTCVD oxides, oxynitrides and nitrides for use in thin sidewall spacer application. Refractive index and etch rate measurements suggest that oxides deposited with a 2 % flow rate ratio of SiH 4 /N2O and annealed at 900 °C for 10 seconds produces films with excellent structural quality. Refractive index and wet etch rate both exhibit a linear dependence with the gas flow ratio. An increase in deposition pressure decreased the refractive index while increasing the etch rate. Oxide and oxynitride dielectrics formed using SiH 4 had a much superior step coverage over a wide range of aspect ratios than TEOS dielectrics. Dit and breakdown fields for oxides and oxynitrides with 3 atomic % nitrogen were comparable to that of thermal oxide indicating their good electrical quality. The results reported suggest that RTCVD sidewall spacers are a promising candidate for use in future MOSFET devices.
Optimization of Process Parameter and Temperature Uniformity On Wafers For Rapid Thermal Processing
Authors: Tillmann Andreas
Published: April 2011

A new strategy based algorithm to optimize process parameter uniformity (e.g.sheet resistance, oxide thickness) and temperature uniformity on wafers in a commercially available Rapid Thermal Processing (RTP) system with independent lamp control is described. The computational algorithm uses an effective strategy to minimize the standard deviation of the considered parameter distribution. It is based on simulation software which is able to calculate the temperature and resulting parameter distribution on the wafer for a given lamp correction table. A cyclical variation of the correction values of all lamps is done while minimizing the standard deviation of the considered process parameter. After the input of experimentally obtained wafer maps the optimization can be done within a few minutes. This technique is an effective tool for the process engineer to use to quickly optimize the homogeneity of the RTP tool for particular process requirements. The methodology will be shown on the basis of three typical RTP applications (Rapid Thermal Oxidation, Titanium Silicidation and Implant Annealing). The impact of variations of correction values for single lamps on the resulting process uniformity for different applications will be discussed.
Rapid Thermal Chemical Vapor Deposition of Nitrogen-Doped Polysilicon for High-Performance and High-Reliability CMOS Technology
Authors: Sun S. C. , Wang L. S. , Yeh F. L.
Published: April 2011

In this paper, a detailed study is presented for the growth kinetics of rapid thermal chemical vapor deposition (RTCVD) of nitrogen-doped polysilicon using silane and ammonia chemistry. It is found that nitrogen doping has reduced the surface roughness and grain size of the RTCVD polysilicon film. Both the deposition rate and the incubation time of film growth depend strongly on the ammonia to silane flow ratio. We have proposed a novel structure of NICER (Nitrogen Incorporation into CMOS Gate Electrode by in-situ RTCVD). High performance and highly reliable dual gate CMOS can be formed by combining rapid thermal oxidation (RTO) with RTCVD.
N-Channel Mos Transistors below 0.5 μm with Ultra-Shallow Channels formed by Low Temperature Selective Silicon Epitaxy
Authors: Huang P. L. , Seastrand K. , Violette K. E. , Wolf J. , Öztürk M. C.
Published: April 2011

In this paper, we present an application of ultra high Vacuum Rapid Thermal Chemical Vapor Deposition (UHV-RTCVD) to MOSFET channel engineering. MOSFETs were fabricated on ultra-thin (200 Å), moderately doped (l×1017 - 6×1018 cm−3) p-type epitaxial layers selectively grown in active areas defined by standard LOCOS isolation. The selective epitaxy was achieved using a novel Si2H6Cl2/B2H6 process at 800°C and at a total pressure under 30 mtorr. Low thermal budget processing techniques were emphasized to minimize spread in the channel doping profile. Threshold voltages below 0.6 V were obtained. Transistors with effective channel lengths of 0.45 μm exhibit subthreshold slopes from 78 to 92 mV/decade determined by the epitaxial channel doping density. We have found that by using ultra-thin channels, expected transconductance degradation at high channel doping densities can be minimized. Furthermore, ultra-thin channels help reduce the sensitivity of the threshold voltage on substrate bias. The results show that low temperature selective silicon epitaxy can be used to form ultra-shallow channel doping profiles that can enhance the performance of MOSFETs in the deep submicron regime.
Formation of Raised Source/Drain Junctions by Rapid Thermal Chemical Vapor Deposition
Authors: Öztürk Mehmet C. , Wortman Jimmie J.
Published: April 2011

In this paper, we present alternative uses of rapid thermal chemical vapor deposition (RTCVD) in forming junctions for the raised source/drain MOSFET. The results will include applications of epitaxial silicon, SixGe1−x and TiSi2 all selectively deposited in dedicated coldwalled, lamp heated high or ultra high vacuum RTCVD reactors. Two general approaches will be considered : 1) ultra shallow junction formation in silicon followed by a selective deposition process to form a raised contact, 2) selective deposition to obtain a layer that can be used as a solid diffusion source and as a sacrificial layer for self-aligned silicide formation. In the first approach, junctions are formed typically by low energy ion-implantation. In this paper, we present rapid thermal vapor phase doping (RTVPD) as an alternative to ion-implantation to form defect free ultra-shallow junctions in Si. The method involves exposing a silicon wafer to a dopant gas (such as B2H6) at a moderate temperature (∼600°C) for a short time and subsequent annealing for drive-in. This is followed by either selective epitaxy and conventional self-aligned TiSi2 formation or selective deposition of a low-resistivity C54 TiSi2 from TiCl4 and SiH4. In the second approach, first, a semiconductor (Si, polysilicon or SixGe1−x) is deposited selectively. If the material is undoped, doping can be achieved by ion-implantation. In-situ doping is also possible as will be shown with p- and n-type SixGe1−x at temperatures as low as 625°C using B2H6 or PH3. The doped layer is then used as a solid diffusion source to form the junctions by out-diffusion. Using these different approaches, we present examples of high quality junctions in Si as shallow as a few hundred angstroms. The techniques are compared based upon their robustness, complexity, equipment and thermal budget requirements.