bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on Ion Scattering and Sputtering Processes Relevant to Ion Beam Sputter Deposition of Multicomponent Thin Films
Authors: Auciello O. , Ameen M. S. , Krauss A. R. , Kingon A. I. , Ray M. A.
Published: March 2011

Results from computer simulation and experiments on ion scattering and sputtering processes in ion beam sputter deposition of high Tc superconducting and ferroelectric thin films are presented. It is demonstrated that scattering of neutralized ions from the targets can result in undesirable erosion of, and inert gas incorporation in, the growing films, depending on the ion/target atom mass ratio and ion beam angle of incidence/target/substrate geometry. The studies indicate that sputtering by Kr+ or Xe+ ions is preferable to the most commonly used Ar+ ions, since the undesirable phenomena mentioned above are minimized for the first two ions. These results are used to determine optimum sputter deposition geometry and ion beam parameters for growing multicomponent oxide thin films by ion beam sputter-deposition.
Importance of Surface Preparation in Direct Ion Beam Deposition(Ibd)
Authors: Miyake Kiyoshi
Published: March 2011

Fundamental aspects of direct ion beam deposition (IBD) are discussed, stressing surface preparation and contamination problems. Residual gas contamination, ion beam induced metal contamination, and presence of surface native oxide before deposition are shown to be the major factors hindering low temperature epitaxial growth in IBD.
A low energy hydrogen ion bombardment is demonstrated as an effective surface preparation method to remove surface native oxide in the case of silicon deposition.
Study of the Anodic Oxidation on Ti and Ta6V (Ti6A14V) by Ion-Implanted Xe Ions Markers and O18 Tracing Techniques
Authors: Chen Heming , Dai Mingjiang , Bai Xinde , Li Wangpei
Published: March 2011

The techniques of single and double layers of implanted Xe ions marker as well as the O18 tracing method are used to study the mechanism of the anodic oxidation of Ti and TA6V (Ti6A14V). It is observed that in 5 wt% ammonium citrate, the mechanism of the anodic oxidation of Ti is very different from that of TA6V. For Ti, new oxide is formed mainly by the migration of Ti cations to the solution/oxide interface and the regions at which new oxide is formed are at the solution/oxide interface and in the pre-oxide near the interface. While for TA6V, anodic film growth is due to the migration of oxygen anions to the oxide/metal interface and the growth regions of new oxide are at the oxide/metal interface and in the pre-oxide near the interface. Transport numbers for Ti oxidized in 1 wt%. KOH are calculated and found to be affected by oxidation temperature, i.e. at 3'C, the average transport number is 0.32, while at 30&00B0;C,it is 0.28. Current efficiencies are above 99.8%. AES spectra show that the distribution profiles of the elements V and Al in anodic film on TA6V are uniform.
Thermodynamic Measurements via Time-Resolved Transient Conductance
Authors: Thompson Michael O.
Published: March 2011

Recent applications of the transient conductance technique to measurements of thermodynamic properties of Si are reviewed. The transient conductance measurements provide time-resolved data of the melt and solidification dynamics during pulsed laser irradiation. By studying these dynamics, thermodynamic properties can be measured in time and temperature regimes unaccessible by conventional techniques. Examples discussed include homogeneous nucleation, electrical properties of the supercooled liquid, and the melting temperature of amorphous Si. Homogeneous nucleation occurs at supercoolings of 500 K for quench rates near 1010 K/s, consistent with a liquid/crystal surface energy of 0.34 J/m2. Evidence of transient nucleation effects are observed at quench rates above 2 × 1010 K/s. During supercooling, the temperature dependence of the electrical conductivity of liquid Si was estimated between 1200 and 1800 K with a broad maximum observed near 1450 K. The melting temperature of amorphous Si was determined to be 220 K below the crystal melting temperature with no detectable differences between thermally unrelaxed and relaxed states.
Laser Induced Solid-State Grain Growth in Polysilicon Films
Authors: Ajuria S.A.
Published: March 2011

We report studies done on the heating of polysillcon thin films below the melting temperature with long-time (on the order of minutes) continuous-wave laser irradiations. It is shown that a well controlled steady-state temperature is locally established within the film. A thermal model is developed to correlate film temperature to beam intensity and a direct relationship is found. A correlation coefficient of 2.5 K/W/cm2 is empirically determined between film temperature and incident beam power density.
Femtosecond Laser Melting of Graphite and Diamond
Authors: Reitze D. H. , Ahn H. , Wang X. , Downer M. C.
Published: March 2011

Femtosecond time-resolved reflectivity measurements performed on highly oriented pyrolytic graphite (HOPG) and diamond elucidate the nature of the phase transition from solid to liquid carbon. In HOPG, we find that a high-reflectivity phase lasting as long as 10 ps appears when the surface is irradiated with pulse fluences in excess of 0.13 J/cm2, the critical fluence for melting. This transforms within 30 ps into an equilibrium low-reflectivity phase lasting hundreds of ps, similar to behavior observed in picosecond reflectivity experiments. The results suggest the occurrence of a two-step phase transition (graphite -> liquid metal -> liquid insulator) when HOPG is excited above the critical fluence. Similar results are obtained with diamond.
Microstructure, Stress and Electrical Properties of the Highly Stable W/P+-In0.53Ga0.47 as Ohmic Contacts
Authors: Katz A. , Maher D. , Thomas P.M. , Weir B.E. , Dautremont-Smith W.C. , Kimerling L.C.
Published: March 2011

Non-alloyed refractory ohmic contacts to P+-ln0.53 Ga0.47 As layer have been fabricated using sputtered W and rapid thermal processing. These contacts showed excellent thermal stability over the temperature range of 300 to 750°C, with an abrupt and almost unreacted metal-semiconductor interface. The W film biaxial stresses were found to be strongly depended on the Ar pressure during the sputter deposition. At low Ar pressures the film were deposited with compressive stress, and became tensile at pressures higher than 7mTorr with a maximum value of about 8×l09 dyne cm2 as a result of Ar deposition pressure of 28mTorr. The W contacts to Zn doped 1×1019 cm−3 In0.53GA0.47 As film was found to be ohmic already as deposited with a minimum specific resistance of about 7.5×10−6 Ωcm−2, achieved as a result of heating at 600°C for about 30 sec.
Interaction Between Implanted Ions and Intrinsic Defects in Silica
Authors: Magruder R.H. , Kinser D.L. , Weeks R.A. , Zuhr R.A.
Published: March 2011

High purity silica (Spectrosil) samples were implanted with Ti, Cr, Mn, Fe and Cu at doses ranging from 1.0 to 5.0×1015 ions/cm2 at 160 keV and 2.6 μA/cm2. The optical absorption extinction coefficients per ion were measured from 1.8 to 6.0 eV. In all samples there was an increase in absorption over the unimplanted sample at energies ≥4.6 eV. The increase in absorption at 5.1 eV and 5.7 eV is attributed to B2(E”) centers and E’ centers respectively. The relative values of the extinction coefficients of these bands are attributed to the relative oxygen activities of the TMI relative to the SiO2 host substrate.
Optical Waveguide Fabrication by Stoichiometric Implantation of Ti and O into LiNbO3
Authors: Pokers D. B. , Xia W.
Published: March 2011

X-cut substrates of LiNbO3 have been implanted at 500°C with Ti and O to doses of 2.5 and 7.5×l017 ions/cm2, respectively. The high substrate temperature during implantation ensures dynamic recrystallization, preserving the crystallinity of the LiNbOs-The stability of the stoichiometric implants is enhanced sufficiently that annealing at 1000°C proceeds with no surface degradation of the substrate. Annealing under identical conditions without the 0 implant usually results in phase separation of an oxide at the surface, even when annealing is performed immediately following implantation. Samples implanted with Ti and O to preserve the stoichiometric metahoxygen ratio of the substrate can be stored at room temperature for several months without phase separation. Planar optical waveguides have been produced by stoichiometric implantation followed by annealing in water-saturated oxygen for one hour at temperatures of 900 and 1000°C. The sample annealed at 900°C supported a single lossy mode, while the 1000°C sample supported two propagating modes and one lossy mode at λ=0.6μm.
Ion Implantation-Induced Amortization of Ceramic Oxides
Authors: Pedraza D.F.
Published: March 2011

A mechanism of amorphization by ion implantation in ceramic oxides is studied using a rate theory approach. It is proposed that the production of highly localized lattice distortions causes lattice destabilization and the ensuing transition to the amorphous state. These distortions can be caused by a large point defect buildup. It is argued that point defect retention occurs because of the impossibility of producing antisite defects. It is proposed that point defects on each sublattice can shield or trap point defects on the other sublattice. Similarly, metallic impurities may shield oxygen vacancies or trap oxygen interstitial ions, preventing anion Frenkel pairs from recombining. These effects are modeled in a-alumina for low temperature implantations (e.g., around 78 K), where point defects are immobile. It is shown that, at these temperatures, recombination is strongly hindered by the radiation-induced point defects themselves, rather than by the implanted impurities. The high point defect concentration attained by this mechanism is sufficient to raise the free energy of the crystal above the free energy of the amorphous solid.
Ion Implant Activation and Redistribution in AlxGa1–xAs
Authors: Pearton S. J. , Hobson W. S. , Von Neida A. E. , Haegel N. M. , Jonesf K. S. , Morrisft N. , Sealytt B. J.
Published: March 2011

The electrical activation characteristics of implanted Be, Mg, Si and S in AlxGa1–xAs (x = 0-1) were investigated as a function of ion dose for rapid annealing in the range 600-950°C. The apparent activation energy for electrical activity of these species increases with increasing AlAs mole fraction - for Be, the activation energy is 0.35eV for GaAs and 0.49eV for Al0.54Ga0.46 As. There is no evidence for pairing of Be and O in AlGaAs, in contrast to the situation for GaAs. Self-compensation is the predominant limiting mechanism for Si activation in AlGaAs as determined by the relative photoluminescence intensities of the SiGa-to-SiAs related transitions. No significant redistribution of implanted Si is observed for any AlAs mole fraction for rapid annealing (5 sec) up to 900°C, whereas S shows motion into the AlGaAs and no tendency to outdiffuse. By contrast, both Be and Mg display loss of the dopant to the surface, and little redistribution toward the bulk. Minimal damage is observed by transmission electron microscopy in as-implanted AlGaAs for Be or Si doses below the amorphization threshold. Upon annealing at the conditions for optimum activation, a high density of small dislocation loops is observed near the end of the ion range.
The Structure and Properties of Ni Films Grown By Ion Beam Assisted Deposition
Authors: Kant R.A. , Chambers G.P. , Sartwell B.D.
Published: March 2011

Electron-beam evaporated nickel was deposited onto sapphire or rocksalt substrates at room temperature with and without simultaneous argon ion bombardment. The ion energies were 100, 500, or 1500 eV, with ion-to-atom arrival ratios, R, ranging from 0.01 to 0.1. For each film, the microstructure, density, resistivity, and amount of retained argon was measured. It was determined that 100 eV bombardment produced an increase in density with little change in resistivity, whereas 1500 eV bombardment decreased the density and increased the resistivity monotonically with R. The reduction in density was correlated with decreasing microstructural feature size and decreased preferred orientation which suggested that the ions induced an increase in the volume fraction of boundaries.
Ion Channeling Measurements on Germanium Implanted and Annealed Silicon
Authors: Johnson E.A. , Namavar F. , Cortesi E. , Culbertson R.J.
Published: March 2011

We have prepared GexSi1-x/Si structures by implanting germanium into silicon <100> surfaces and thermally annealing. Implant energies were 100 and 150 keV and the total ion doses were between 1 and 10 × 1015 ions/cm2. Ion channeling studies of these structures indicates that after annealing, the germanium atoms substitute into the silicon lattice and create a pseu-domorphic strained layer. In addition, channeling results suggest a residual band of dislocations at or beyond the ion range in the as-annealed samples.
Ion Implantation Induced Effects at Polysdlicon Gate Feature Edges
Authors: Stinson M. G. , Smith P. L. , Osburn C. M.
Published: March 2011

Recently, an enhanced leakage associated with ion implantation at polysilicon gate edges has been reported (1). In this study, TEM and SIMS characterization have been done to supplement electrical measurements in order to better understand the degradation. SIMS, XTEM, and TRIM analyses of arsenic implants through 7 nm gate oxides show considerable ion mixing. A roughening of the underlying silicon substrate leads to asperities which are believed to play an important role in enhancing leakage (2). XTEM analysis of a polysilicon gate edge also reveals the effects of volume expansion associated with the incorporation of both dopant and knock-on oxygen.
Rbs Studies of Damage Behavior in Silicon Induced By P2+ Implantation
Authors: Genqing Yang , Chenglu Lin , Ziwei Fang , Zuyao Zhou , Shichang Zou
Published: March 2011

The damage behavior of <100>-Si implanted with P2+ and P+ ions at equivalent energies were investigated by 2MeV He* backscattering and channeling analysis. Different incident energies (25-90keV/atom) and intermediate doses (1013–1014/cm2) were used for the implantation with sample holder being kept at temperatures ranging from 77k to 483K. It has been shown that the damage created by P2* implants is always greater than that of P2+ implants when the dosage is below the threshold fluence at which amorphization takes place. This damage enhancement phenomenon is strongly related to implantation temperature. A striking damage enhancement induced by 90 keV/atom P2+ implants in the surface region of the sample was observed, and it has been attributed to the multiple collision effect between diatomic ions and host atoms.
Concentration Dependence of Arsenic on Solid Phase Epitaxial Regrowth of Amorphous Silicon
Authors: Jeon Young-Jin , Becker M. F. , Walser R. M.
Published: March 2011

In this work we measured the functional dependence of the solid phase epitaxial (SPE) regrowth rate, V, of amorphous silicon on the concentration of implanted arsenic (n-type) impurity, NAs. The SPE regrowth rates of self-ion amorphized layers in silicon wafers with (100) substrate orientation were measured by in situ, high precision, cw laser interferometry during isothermal annealing for temperatures from 470 °C to 580 °C, and concentrations in the range 1.5×1018cm−3 ≤NAs≤3.5×1020 cm−3.

In the concentration range 7×1018 cm−3≤NAs≤2.2×1019 cm3, selected from the medium dose sample, the SPE regrowth data satisfied a linear equation; V/Vi=1+NAS/Ni, where Ni(T) was fit to an Arrhenius form obtained from the temperature dependent intersections of the SPE regrowth rate data with the concentration axis and Vi(T) was the temperature dependent apparent intrinsic SPE regrowth rate at zero impurity concentration. A similar linear dependence was obtained earlier for boron (B) and phosphorus (P).

However, unlike B and P, an enhancement of SPE regrowth was observed for samples implanted with As in the concentration range 3×1018 cm−3 ≤NAS≤ 1.3×1019 cm−3, selected from the low dose sample. This result indicates that arsenic implanted at low dose levels has a higher fractional ionization in amorphous silicon than either boron or phosphorus implanted at the same dose.

In the high dose samples with arsenic concentrations ≤NAs 2.2×1019 cm−3, the SPE regrowth rate varied nonlinearly with NAS. The nonlinear function had a negative curvature similar to that observed previously for P.
The Effect of Microstructure in the Morphology and Kinetics of Amorphization Induced by Ion Irradiation
Authors: Pedraza D.F. , Maziasz P.J.
Published: March 2011

NiTi was irradiated with Ni ions to study the rate of amorphization as a function of temperature and to determine the temperature cutoff for the crystalline-to-amorphous transition. A series of irradiations was conducted at different temperatures from ambient to 350 °C. Prior to irradiation, the specimens contained martensitic plates and austenitic (B2) regions. However, during irradiation at temperatures of 80 “C and higher, all the specimens were entirely austenitic. As expected, amorphization was delayed as the irradiation temperature was increased. The fraction of material that became amorphous after irradiation at 250 °C to a dose of 0.7 dpa was estimated to be 5 to 10%. Specimens irradiated at higher temperatures remained crystalline, even after doses as high as 4 dpa. Irrespective of the irradiation temperature, we found a non-uniform distribution of amorphous regions that exhibited a morphology closely resembling the shape of the martensitic plates that existed in the material prior to heating it to the irradiation temperature. These observations are discussed in terms of the influence of structural defects on the kinetics of amorphization.
Metastable Phase Formation in the Ti-rich end of the Ti-(Co,Ni) System
Authors: Lilienfeld David A , Bergesen Peter
Published: March 2011

The Ti-rich end of the Ti-(Co,Ni) was investigated by ion mixing. A metastable FCC phase was discovered which formed over a broad composition range. The stable phase was formed by ion mixing at 350°C in some samples but was not formed until 550°C during in situ heating in the Transmission electron microscope. Some of the Ni-rich ternary alloys did not amorphize even after liquid nitrogen ion irradiations. This result indicates that the amorphization mechanism for the TiNi CsCl phase is different from that of the TiCo CsCl phase.
Study of Hf Diffusion in A-Zr using Rutherfdrd Bacckscrttering Spectroscopy
Authors: Dyment F. , Behar M. , Oners H. , Grande P.L. , Savino E. , Zawislak F.C.
Published: March 2011

The present contribution reports on measurements of the diffusion coefficients of Hf in a-Zr via the RBS technique. 250 8 Hf thin films were deposited on two kinds of polycrystalIine Zr samples and annealed in a 773-1115 K temperature range. Our results show that in both cases, the diffusion coefficients follow curved flrrhenius plots. On the other hand for the purest Zr sample we have obtained diffusion coefficients that are systematicaly and significativel ly lower than those corresponding to the Zr sample richer in impurities.
Metastable Structures Formed in Plasma Source Ion Processing
Authors: zheng Xiao-Ci , Dodd R. A. , Conrad J. R.
Published: March 2011

Ni-Ti films were bombarded by plasma source heavy ions of different ion dose and ion flux. Disc-like non-uniform microstructures were found when the films were irradiated at a dose of 5x1016Kr+/cm2. These “discs” were acting as defect centers. The development of “discs” depended on the plasma ion flux during the pulse. Target geometry appeared to have effects on the density of “discs”.
Residual Stress in and Microstructure of Fe and Ti Surface Layers After 1 Mev N+ Implantation at High Dose
Authors: Vredenberg A.M. , Saris F.W. , Pers N.M. v.d. , Colijn P.F. , de Keijser Th.H. , Mittemeijer E.J.
Published: March 2011

The effect of 1 MeV N+ irradiation on the microstructure of Fe and Ti specimens was investigated. The Fe and Ti specimens were implanted such that the N peak concentration (30 at.% in Fe, 45 at.% in Ti), was below the concentration of N in ε-Fe2N and δ-TiN, respectively. X-ray diffraction phase analysis showed that ε-Fe2N and δ-TiN had formed. X-ray diffraction stress analysis indicated that the residual stress in the Fe and Ti matrices was negligible after implantation. This suggests that the volume misfit due to nitride formation had been accommodated by plastic deformation. Indeed, surface profilometry of implanted Fe showed that a volume increase of the specimen had occurred which was compatible with the formation of unstrained nitride .
On the Stability of Hetastable and Amorphous Pvd-Compound Films
Authors: Knotelc Otto , Jungblut Frank , Barimani Arman
Published: March 2011

In using low temperature physical vapour deposition (PVD) techniques new metastable and amorphous materials can be deposited. Structural order in a coating is produced largely by the mobility of the adatoms. Low mobility does not allow the formation of equilibrium phases and metastable and/or amorphous structures are observed. These coatings have sufficient thermal stability for tools, and for both wear- and corrosion-protection. Examples are given within the systems Al-O-N, Ti-Al-N and Cr-Al-N and the properties, crystalline and thermodynamic state of the coatings are characterized. An example of decomposition phenomena is given in metastable thin coatings by the Ti-Zr-N system.
Excimer Laser Induced Deposition of Tungsten from W(CO)6 and WF6
Authors: Rager Berthold , Bachmann Friedrich
Published: March 2011

ArF laser induced deposition of W from W(CO)6 and WF6 on Si/SiO2 surfaces was investigated. With an in-situ reflectivity measurement the growth of the layer could be monitored during the deposition process. We find that the initial stage of layer growth as well as the reflectivity as a function of deposition time depends on the laser fluence and on other deposition parameters. Model calculations, using the optical constants of deposited films, determined by ellipsometry, have been performed to compare the measured reflectivity curves with the calculated curves. The deposited layers have been analyzed by XPS, AES, X-ray Diffraction and Raman Spectroscopy. Additionally, experiments of direct pattern transfer deposition (via contact mask) with W(CO)6 show the presence of an involved surface process, which by Fresnel diffraction caused structures smaller than 0.5μm.
Roles of Gas Phase and Surface Photolysis in Laser Chemical Vapor Deposition from Fe(CO)5
Authors: Xu Xin , Steinfeld J.I.
Published: March 2011

The chemical state of the carbon and oxygen incorporated in iron films formed by laser photolysis of Fe(CO)5 has been examined by profiling XPS analysis. A significant portion of the codeposited CO is photodissociated at the growing surface.
Metal Deposition with Incoherent Excimer Radiation
Authors: Esrom Hilmar , Kogelschatz Ulrich
Published: March 2011

VUV light-induced decomposition of palladium acetate films was performed by using a new incoherent excimer source. With pure xenon this excimer source emits radiation peaking at a wavelength of 172 nm. We investigated mainly the palladium deposition from spin-on palladium acetate films on aluminum oxide substrates. By using EMP we determined the palladium thickness as a function of UV intensity and exposure time. A remarkable temperature effect of the photolytic deposition process was observed also in a temperature range in which no thermal decomposition is possible. The exposure of spin-on palladium acetate films on ceramic substrates was also accomplished through metal contact masks. Patterned palladium films were reinforced by electroless copper and nickel plating processes [1]. The obtained structures had the same high edge quality as those produced by using excimer lasers [2].
Electronic Excitation-Induced Surface Chemistry and Electron-Beam-Assisted Chemical Vapor Deposition
Authors: Bozso F. , Avouris Ph.
Published: March 2011

Selective area deposition of thin films and surface structures with precise control over their composition is possible in UHV by using low energy electron beams to induce electronic excitations in adsorbed molecular layers. Upon electron impact, adsorbed/co-adsorbed molecules decompose into reactive species, resulting in film growth. The composition of the film reflects that of the adsorbed molecular layer, which at cryogenic temperatures can sensitively be controlled by the partial pressure of the reactant gases. We present results of detailed studies of adsorption, thermal and electron-beam-induced dissociation of disilane and ammonia on silicon. We show that by proper choice of temperature, gas phase composition and electron beam, amorphous silicon, silicon nitride, oxide, silicon oxinitride films can be grown with nearly monolayer thickness resolution.
Maskless Formation of Tungsten Films by Ion Beam Assisted Deposition Technique
Authors: Xu Zheng , Kosugi Toshihiko , Gamo Kenji , Namba Susumu
Published: March 2011

W films were deposited on n-GaAs by ion beam assisted deposition technique using low energy H2+ and Ar+, and film properties and residual damage in the substrate were investigated by measuring X-ray photoemission, current-voltage characteristics and deep level transient spectroscopy. Films with a resistivity of 1O−5 ohm·cm were formed. It was observed that damage can be reduced using the low energy beams and that Schottky contacts with n-factor of almost 1 and barrier height of 0.88 eV were formed.
Selective Chemical Vapor Deposition of Tungsten Films on Titanium—Ion—Irradiated Silicon Dioxide
Authors: Okuhira H. , Nishimatsu S. , Ninomiya K.
Published: March 2011

Selective area depositon of adherent tungsten (W) film on titanium (Ti)—ion—irradiated silicon dioxide (SiOz) is achieved. First, Ti—ion irradiation through a stencil mask is performed at 600 eV for 1.1 X 1016 atoms/cm2 in a reaction chamber. Next, ArF excimer laser (λ = 193 nm) chemical vapor deposition (CVD) with tungsten hexafluoride (WFs) and hydrogen (H2) is carried out for 40 seconds at 400 K. Finally, low—pressure (LP) CVD is carried out at 600 K and then W films are deposited selectively on the ion—irradiated SiO2 Without the laser CVD step, the ion—irradiation pattern disappears during LPCVD and no W film deposition occurs. Therefore, laser CVD is essential in our experiments.
Laser Processed Silicides for GaAs Hemts
Authors: Anderson W.T. , Christou A. , Thompson P.E. , Davis J.L. , Gossett C.R. , Eridon J.M. , Michelakis C. , Kiriakidis G. , Hatzopoulos Z. , Ethimiopoulos T. , Kudumas D M. , Morgan D.V.
Published: March 2011

Laser annealed refractory metal gates and Ohmic contacts have been developed for GaAs FETs and HEMTs fabricated on MBE layers grown on laser desorbed substrates. Amorphous refractory metal silicide films were sputter deposited by a method in which the RF power to separate refractory metal and silicon targets were set at predetermined deposition ratesand the substrates were rotated with respect to the sputter targets receiving a 0.2 to 0.5 nm film on each pass. The gate resistance was reduced and Ohmic contacts formed by pulsed excimer laser annealing.
Novel Photoimaging Schemes at Polymer Surfaces: Their Role in High Resolution Lithography
Authors: Taylor Gary N. , Nalamasu Omkaram , Hutton Richard S.
Published: March 2011

Polymer surfaces play essential roles in many technical arenas, but their importance in imaging science and technology has only recently been established. As optical lithography for integrated circuit applications pushes below 0.5μm feature sizes, ever shorter wavelengths and lenses with larger numerical aperatures are required. These narrow the depth-of-focus to such a degree that it eventually becomes less than the substrate topography, resist film thickness and wafer nonuniformity contributions to focus placement. Thick single-layer, surface-conforming resists will not be able to record the aerial image accurately.

Surface imaging of planarized single-layer or bilayer organic films offers a means for minimizing the depth-of-focus constraints. This paper outlines this general concept which includes radiation-induced chemical changes in the surface and near-surface regions, amplification of these events by gas-solid reactions with inorganic and organometallic agents and plasma development using an oxygen plasma. Two approaches to surface imaging are discussed. The first employs Plasmask® resist, a very absorbing diazonaphthoquinone-functionalized novolac resin which is exposed and functionalized in the topmost several hundred nm of film. According to Coopmans, Roland and coworkers [14] and Pierrat, et al., [22] two tones are possible depending upon the processing. The present study reports results obtained for both processing modes using 248.4 nm lithography.

The second approach involves imaging at the surface and utilizes one of the oldest polymer photoreactions, photo-oxidation, in the imaging step. Hydrophobic aromatic polymers are first irradiated in air to give hydrophilic groups. These sorb water selectively on the hydrophilic areas. The water is reacted in a separate step with an inorganic or organometallic compound such as TiC14 to give a metal oxide film (TiO2) on the exposed areas. Development with an oxygen plasma gives negative tone patterns because TiO2 reduces the etching rate by a factor of ∼ 500 in the exposed regions. Imaging is dependent upon the polymer structure, among other things, and is optimized at shorter wavelengths likely to be used in future exposure systems. From the present results we feel that surface imaging resists may realize 0.25 μm resolution at 193 nm and that <0.10 μm resolution may be achieved using x-ray radiation.
Control of Etching in Laser—Chemical Reaction of Mn—Zn Ferrite by MeV Ion Implantation
Authors: Takai Y. F. LU. M. , Sanda H. , Chayahara A. , Satou M. , Minamisono T. , Namba S.
Published: March 2011

The change in the behavior of laser—induced etching of Mn—Zn ferrite by MeV ion implantation has been investigated. The etching induced by Ar+ laser irradiation in a H3PO4 solutipn w~s completely suppressed by implanting 3 MeV Au+ to a dose of 1x1016 cm-2 when the laser induced local temperature rise was below the melting point of the ferrite. The etching suppression disappeared when the Au+ implanted sample was thermally annealed at 900 ºC for 30 min. The suppression is found to be related to the crystallinity change induced by ion implantation.
Selective Etching and Photo—Bleaching in Thin Amorphous Ge—Sb—S Films
Authors: Savova Evdokia B. , Pashmakoff B.I.
Published: March 2011

A mechanism is proposed for the selective etching effects in thin amorphous Ge—Sb—S films based on the combined action of photostructural changes and alkaline solvent with a surface active substance. Evidence is given in support of the assertion thatthe same photostructural changes (namely, the breaking of Ge—Sb bonds under the action of UV light) are responsible for the irreversible photo—bleaching of these layers. Four different compositions in the system Ge—Sb—S have been studied under different preparation conditions (thermal evaporation and laser—beam sputtering).Photostructural changes were induced by UV light irradiation. Infrared spectra of the layers are presented in support of the proposed model.
Copper Vapor Laser Used in Etching and Deposition
Authors: Haba Belgacem , Hussey Brian W. , Gupta Arunava , Baseman Robert J.
Published: March 2011

We have carried out experiments for etching manganese-zinc ferrite in aqueous KOH solution using a copper vapor laser. The high repetition rate (5-10 KHz), the high peak power (∼ 250 KW), and the short pulse length (24-30 ns) result in rapid etching of grooves with high aspect ratios. The depth of the grooves increased with laser power and slower scan speeds while, the width was limited to the laser beam focus. The etching process is believed to be purely thermal in nature and limited only by the removal of the molten material out of the grooves. The copper vapor laser was also used as a source for projection deposition of various metals on quartz substrate by a pyrolytic process. This system achieved patterns with finefeature sizes, good resolution, and metallic properties of the deposits. In this technique, both the spun-on organometallic films as well as LCVD were tried.
Excimer Laser-Assisted Etching of Silicon Using Chloropentafluoroethane
Authors: Russell S. D. , Sexton D. A.
Published: March 2011

Laser-assisted photothermal chemical reactions have been observed with silicon in a chloropentafluoroethane ambient using a KrF* laser at 248 nm. Etching occurs onlyif the incident fluence exceeds the melt threshold (∼0.75 J/cm2, with the melt duration determined by observing the change in silicon reflectance at 633 nm. Above the ablation threshold (∼2.2 J/cm2) increased surface roughness is observed. Etch rates -7 Å/pulse have been measured using both stylus profilometer and SEM cross-sectional techniques. The etch rate dependence on incident fluence, ambient pressure, doping concentration, crystal orientation and substrate temperature have been examined suggesting an adsorption limited thermal process. This process allows single step patterning of silicon devices in a non-corrosive environment.
Selective Silicon Epitaxy for Advanced Dram Structures
Authors: Bronner Gary B.
Published: March 2011

In silicon microelectronics, memory cells and chips are used to develop the most advanced technology. In the future these chips will require three dimensional structures to achieve the needed density. This paper describes the use of selective silicon epitaxy to build truly three dimensional DRAM cells. The cell consists of a trench capacitor which is overgrown with single crystal silicon. A transistor and isolation are then built above the trench capacitor resulting in a cell that occupies the same area as the transistor alone. Fully functional memory cells have been built. The results show that selective silicon epitaxy is a realistic candidate for building three dimensional silicon devices.
Surface Reaction Mechanisms in Selected Area Epitaxy of II-VIs
Authors: Irvine Stuart J.C. , Hill H. , Hails J.E. , Pitt A.D. , Mullin J.B.
Published: March 2011

Laser-induced selected area epitaxy of CdTe thin films on GaAs substrates has been investigated and the role of vapour phase and surface reactions considered. Photo-enhanced growth rates of CdTe have been measured as a function of UV laser intensity and as a function of Cd to Te alkyl ratios. The growth rates are not simply determined by vapour phase photo-dissociation but also by a photolytic reaction on the surface. The latter enables good pattern definition where the growth rate is enhanced by the incident uv -radiation. The factors that determine the photo-enhancement are considered in the light of the Langmuir-Hinsheltwod model.
Laser Selective Area Epitaxy for the Potential of Optoelectronic Integration
Authors: Liu H. , Roberts J.C. , Ramdani J. , Bedair S.M.
Published: March 2011

We report for the first time the dopant behavior in laser assisted selective epitaxy of device quality GaAs films. DMZn and H2Se were used as p-type and n-type dopants respectively. Uniform doping was achieved by introducing TMGa, AsH3 and dopant gases simultaneously and was accompanied by a decrease in growth rate for both Zn and Se doping. For planar doping, several Se planes were embedded in a GaAs layer by simultaneously introducing AsH3 and H2Se during the LCVD process. A sheet carrier concentration in the 1012 – 1013 cm−2 range was obtained for a single Se plane. Hall data of these films will be discussed. It was found planar doping results in better electrical properties and better growth rate control.
Reactive Ion Etching of In-Based III-V Semiconductors -Comparison of Cl and C2H6 Chemistries
Authors: Pearton S. J. , Chakrabarti U. K. , Baiocchi F. A. , Hobson W. S.
Published: March 2011

The reactive ion etching of InP, InGaAs and InAlAs in CC12F2 /O 2 or C2H6 /H 2 discharges was investigated as a function of the plasma parameters pressure, power density, flow rate and relative composition. The etch rates of these materials are a factor of 3-5 times faster in CC12F2 /O 2 (∼600–1000 Å · min−1) compared to C2H6 /H 2(160–320 Å · min−1). Significantly smoother morphologies are obtained with C2H6 /H 2 etching provided the composition of the plasma is no more than 10 - 20% by volume of C2H6. At higher methane compositions, polymer formation increases leading to micromasking and rough surface morphologies. Sub-surface disorder is limited to <100 Å deep for both gas chemistries for plasma power densities of 0.85 W cm−2. The C2H6 /H 2 mixture leaves an In-rich surface in all cases, but this surface is free of any residual contamination, whereas the CC12F2/O2 chemistry leaves chloro-fluorocarbon residues approximately 20–50 Å thick on the surface of all three In-based materials.
Characterization of Sidewall Residue Film and Atomic Structure of the Trench Formed by BCI3/CI2 Reactive Ion Etching
Authors: Yun Sun Jin , Jeon Young-Jin , Lee Jeong Y.
Published: March 2011

The silicon trench etching in BCl3/Cl2 reactive ion etching plasma leads to the intrinsic bonding damage, the permeations of etching species and impurities into silicon substrates, and the deposition of residue film on trench sidewall. The contaminations and the damages in trench were investigated by using high resolution transmission electron microscopy (HRTEM), secondary ion mass spectrometry (SIMS), and x-ray photoelectron spectroscopy (XPS). The microstructure of the rounded bottom surface showed that the surface region was distorted by 2 - 6 atomic layers and the trench etch was mainly limited by the physical sputtering-like mechanism. The damage in the silicon lattice consisted of prominent planar defects roughly confined to {110} and {111} planes. The thickness of sidewall residue film was 10 - 90 nm, which was thinner at deeper region of the trench, whereas that of residue film at the trench bottom was 1.5 - 3.5 nm. The SIMS results of no-patterned specimen presented that the permeation depths of boron and chlorine into the Si-substrate were about 40 and 20 nm, respectively. The presence of BxCly and Cl-related Si chemical states was identified from XPS analysis of the residue film.
Precursors to the Photo-Ablation of Sodium Trisilicate Glass Due to Uv Excimer Irradiation
Authors: Eschbach P. A. , Dickinson J. T. , Langford S. C. , Jensen L. C. , Pederson L. R. , Baer D. R.
Published: March 2011

On polished sodium trisilicate glass surfaces, a fairly distinct threshold in laser fluence is observed to commence ablative etching. An incubation or induction effect is also seen where a series of laser pulses is required to induce etching. In this paper we examine features of the charged particle emission over a broader range of fluences (in particular, at lower fluences) to identify those factors which control the onset of etching. Laser--free electron heating is proposed as a dominant mechanism.
Low Temperature Laser Physical Vapor Deposition of Multilayered Thin Films
Authors: Biunno N. , Krishnaswamy J. , Sharan S. , Ganapathi L. , Narayan J.
Published: March 2011

We have investigated the formation of various multilayer thin films by the laser physical vapor deposition technique. A multi stage target holder was constructed to perform all process steps in-situ; target/substrate cleaning, deposition, and annealing. The laser physical vapor deposition technique offers many advantages over conventional physical vapor techniques, such as, lower substrate temperature, microstructural control, and very low contamination levels. Film thickness can be controlled from near atomic to micron dimensions. A layer-by-layer (two dimensional) growth can be achieved, resulting in nonequilibrium structures. The films were analyzed using cross-section and high resolution transmission electron microscopy (TEM). The significant reduction in substrate temperature for the formation of high quality multilayer and epitaxial films opens up many new areas of applications requiring reduced thermal-budget processing.
Visible-Wavelength Laser Photodeposition of Cobalt Interconnects
Authors: Rothschild M. , Sedlacek J. H. C. , Shaver D. C. , Ehrlich D. J. , Bittenson S. N. , Edwards D. , Economou N. P.
Published: March 2011

Cobalt interconnects were deposited with a cw visiblewavelength laser from gaseous Co2 (CO)8. The deposited material was high-purity Co, and its electrical resistivity was as low as 13 μΩ-cm (twice that of bulk resistivity). The deposition is initiated by photochemical decomposition of Co2 (CO)8, and therefore process parameters (pressure, power, writing speed) are insensitive to the optical and thermal properties of the substrate.
Laser Chemical Vapor Deposition of W on Si and SiO2/Si
Authors: Lin Jian-Yang , Allen Susan D.
Published: March 2011

Direct write of W on bare Si and native SiO2/Si substrates has been investigated in an laser chemical vapor deposition (LCVD) system. W deposits on bare Si surface via the Si and/or H2 reduction of WF6 were self-limited in thickness to 200 - 600 Å in both cases. Auger electron spectroscopic analysis showed that Si-H bonds could be poisoning the further growth of W. W deposits on native SiO2/Si were only obtainable via the H2 reduction of WF6 in our laser direct-write system. Our experimental kinetic study indicated that HF desorption from the surface is the rate-controlling step for W deposition via the H2 reduction of WF6. The as-deposited W line deposits were 2 - 10 μm wide, 0.2 - 6 μm thick with resistiiities in the range of 11 - 56 μΩ-cm. Growth rates as high as 2.2 mm/s have been achieved.
Very Thin 2D GaAs Films on Si During the Early Stages of Growth by MBE
Authors: Fenner D.B. , Biegelsen D.K. , Krusor B.S. , Ponce F.A. , Tramontana J.C.
Published: March 2011

GaAs samples deposited on Si by molecular beam epitaxy (MBE) with a graded thickness of 0–3 nm initially show the presence of a metastable two dimensional (2D) layer containing Ga and As. In the thicker regions of the wedge samples, islands (3D topography) form in the presence of the 2D sea, i.e., Stranski – Krastanov growth. Compositional profiles of these wedges were made with in situ Auger electron spectroscopy (AES) which has allowed the identification of at least four regimes of growth. Lattice images from cross – sectional transmission electron microscopy (XTEM) are consistent with the AES profiles. Substrate temperature during deposition of the films has a strong effect on film topography, as does the beam – flux ratio on film stoichiometry.
Electronic and Structural Study of Ni(Co) Silicide/Si(111) Contact System Studied by Soft X-Ray Emission Spectroscopy
Authors: Watabe H. , Nakamura H. , Iwami M. , Hirai M. , Kusaka M.
Published: March 2011

An electron excited Si L2,3 valence band soft x-ray emission spectrum (SXES) for Ni(or Co)Si2 showed a clear modification from that for Si. From the SXES study, a fair amount of the Si(3s) valence band density of state (VB-DOS) is concluded to be included in the upper part of the VB-DOS for the transition metal(TM) disilicides due to the TM-Si bond formation, which is a clear contrast to proposals given so far. Non-destructive structural analysis of a NiSi2 (tens of nm)/Si(111) contact is also carried out successfully using the SXES.
Electron Spin Resonance Studies of Silicon Dioxide Films on Silicon in Integrated Circuits Using Spin Dependent Recombination
Authors: Jupina M. A. , Lenahan P. M.
Published: March 2011

The technique of spin dependent recombination (SDR) allows the electron spin resonance (ESR) observation of electrically-active point defects in a single metal-oxide-semiconductor field-effect transistor (MOSFET) with surface areas of only 10-4 cm2 and Si/Si02 interface point defect densities of ∼1011/cm2. With SDR's enhanced sensitivity, devices with different processing details are explored. Differences in the E' spectra for variations in the oxidation processing are discussed.
Si(001) Molecular Beam Epitaxy: Enhanced Diffusion or Bonding?
Authors: Clarke S. , Wilby M.R. , Vvedensky D.D.
Published: March 2011

Through application of a lattice model of the Si(001) surface, implemented in a Monte Carlo growth simulation we investigate the structural evolution of the Si(001) surface during molecular beam epitaxy. Particular emphasis is placed upon identifying the role of both enhanced diffusion and directional bonding.
Observations of Surfaces by Electron Microscopy During STM Operation
Authors: Spence J.C.H. , Knipping U. , Norton R. , Lo W. , Kuwabara M.
Published: March 2011

A scanning tunnelling microscope is described which operates inside a transmission electron microscope in the reflection mode. The device is used to study the mechanism of STM contrast in graphite and semiconductors. It allows for the observation of any strain during tunnelling, using the reflection electron diffraction contrast mechanism. The first results of our new transputer-based digital imaging system for STM are reported.
Direct Observation of A 7×7 Superstructure Buried at the Amorphous-Si / Si(111) Interface
Authors: Sakai Akira , Tatsumi Toru , Ishida Koichi
Published: March 2011

Direct imaging of a 7×7 superstructure buried at the interface between amorphous-Si and a Si(111) substrate was demonstrated by cross-sectional high resolution transmission electron microscopy (HRTEM). The electron diffraction pattern of the interface region in cross-section geometry showed diffuse streaks of fractional order which suggested the existence of the superstructure at the interface. The <110> cross-sectional HRTEM image showed the atomic configuration of the projected interface superstructure, which had a periodicity of 23 Å along the interface. Such periodicity corresponds to 7 times the 1/3{224} periodicity which is 3.3 Å at the interface. The interface atomic model of the buried 7×7 superstructure was also proposed by using the image matching technique between the experimental and computer simulated images.
Study of Interfacial Sharpness and Growth in (GaAs)M(AlAs)N Superlatihces
Authors: Gammon D. , Prokes S. , Katzer D.S. , Shanabrook B.V. , Fatemi M. , Tseng W. , Wilkins B. , Dietrich H.
Published: March 2011

X-ray diffraction, inelastic light scattering, photoluminescence and photoluminescence excitation spectroscopies have been employed to study the effects of growth conditions on the interfacial sharpness of GaAs/AlAs superlattices. In addition to describing which changes in the MBE growth procedures result in the sharpest interfaces, this study addresses the relative strengths and weaknesses of the experimental probes employed in the examination of interfacial irregularities.
A Study of Interfaces in GaAs/AlAs Superlatyices Using Phonons
Authors: Gammon D. , Shanabrook B.V. , Prokes S. , Katzer D.S. , Tseng W. , Wilkins B. , Dietrich H.
Published: March 2011

Vibrational Raman scattering has been used in conjunction with luminescence, luminescence excitation spectroscopy, and x-ray diffraction to study the interfaces of GaAs/AlAs superlattices grown by MBE with and without growth interruptions at the interfaces. The confined LO phonon spectra clearly indicate that in the sample grown with growth interrupts at least one of the interfaces in each GaAs layer is truly smooth. In addition it is shown that the intensity of the interface phonons probed via Raman scattering is sensitive to the state of the interface.
On the Atomic Structure of Boundaries in Very Small Metallic and Bimetallic Particles
Authors: Jose-Yacaman M. , Avalos M. , Vazquez A. , Tehuacanero S. , Schabes P. , Herrera R.
Published: March 2011

The study of boundaries in small particles is of great interest in areas such as catalysis, metallurgy and surface science. A particularly interesting case is that of metallic particles containing one or several metals. In the present work we present a number of examples of different mono and bimetallic systems.