bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and Properties of Gallium Phosphide Doped by Rare-Earth Elements
Authors: Pyshkin Sergei L. , Anedda Alberto
Published: March 2011

GaP single crystals have been grown from 5at.% solution of P in Ga with (0.01-0.1)at.% of La, Sm or Gd as dopants. Electric properties, photoconductivity and luminescence of the crystals have been investigated by standard methods.

Energy levels of impurities, mobility and concentration of current carriers have been determined in wide temperature region. It was shown that nitrogen (N) and other uncontrolled impurities present in the crystals due to some peculiarities of crystal growth. The intrinsic RE impurity luminescent spectra can be seen only together with spectra of excitons bounded on N traps. The evaluation of quantum eficiency for RE impurity made on the base of luminescence decay measurements gives the value close to 1. The interpretation of GaP:RE luminescence spectra is presented as intrashell transitions activated by bound exciton recombination as well as D-A and D-valency band transitions between some contaminating impurity (donor) and RE element (acceptor).
Mocvd Erbium Sources
Authors: Greenwald Anton C. , Rees William S. , Lay Uwe W.
Published: March 2011

The overall objective of this research is to develop source materials for doping AIGaAs. We compared Er(C5H5)3 to Er{N[Si(CH3)3]2)3 for purity, decomposition kinetics and doping of germanium films deposited from Ge(CH3)4 in a hydrogen atmosphere. Cyclopentadienyl erbium left large amounts of carbon both in pure metal films, and in the germanium film, at low pressure and temperatures to 850°C. Bis-(tri-methylsilyl) erbium amide decomposed cleanly without carbon, nitrogen or silicon in the deposited film.
Esr of Rare Earth Impurities (Dy3+, Er3+, Yb3+) in The Narrow Gap Semiconductor PbTE.
Authors: Gennaro A.M. , Martins G.B. , Rettori C. , Barberis G.E. , An C.Y.
Published: March 2011

Electron Spin Resonance experiments of several diluted rare-earths (Dy3+, Er3+, Yb3+) in the narrow gap semiconductor PbTe show ground states appropriated with a cubic crystal field splitting of the lowest multiplet (J). The data permits the determination of the sign and ratio of the cubic crystal field parameters A4 and A6< r6 >. These results suggest that the rare-earths substitute the Pb2+ ions and that the crystal field is mainly associated to an octahedron of Te2− ions. The observed ESR spectra also show lower symmetry sites probably associated with nearest neighbor Pb2+ vacancies.
Tie Effect of Rare-Earth Elements on the Entroy of Radiation Defects Ionization in N-Type Go
Authors: Petrov V.V. , Kharohenko T.D. , Yavid V.Yu.
Published: March 2011

Te analyses of the processes of radiation defect formation in germanium doped with phosphorus in the presence of rare-earth element neodimium and without it has been carried out.It has been shown that the presence of neodimium in n-Ge results in the change of enthalpy and entropy of the major radiation defect ionization (complex with the level being near EB-0.20 eV). The change of enthalpy by 0.03-0.04 eV as well as more than six fold increase of entropy of the complex ionization in Ge:Nd has been stated to be connected with the local deformation of the lattice around defect formed in the process of irradiation.
Annealing Studies of Er-Implanted GaAs and the Excitation Mechanism of Er in GaAs
Authors: Elsaesser D. W. , Colon J. E. , Yeo Y. K. , Hengehold R. L. , Pomrenke G. S.
Published: March 2011

Electrical and optical measurements were performed on p-type GaAs implanted with 1013 Er ions/cm2 at an energy of 1 MeV. The samples were annealed at 650, 750, 850, or 900 °C for 15 seconds using the rapid thermal annealing technique. Although annealing at 650 °C was insufficient to recover measureable electrical conductivity in the implanted region, Er3+ 4f-4f emissions were still observed. Annealing at 750 TC produced a large concentration of hole traps at EV + 360 meV, and the most intense Er-related emissions at 1.54 μm. The two higher annealing temperatures returned the implanted region to the conductivity of the substrate but resulted in weak Er-related emissions. Two distinct Er-related centers were found, and they are believed to be the cause of the intense and weak emissions, an Er-interstitial and Er substituting for Ga, respectively.
Photoluminescence Study of Energy Transfer Processes in Erbium Doped AlxGal−xAs Grown by MBE
Authors: Zhang Tong , Sun J. , Edwards N.V. , Moxey D.E. , Kolbas R.M. , Caldwell P.J.
Published: March 2011

Sharp photoluminescence from the intra-4f shell of Er3+ is observed from erbium doped AlxGal-xAs (0 ≤x ≤ 1) grown by molecular beam epitaxy. The intensity of the luminescence from the erbium is strongly dependent on the aluminum composition with a maximum at x ≈ 0.6. We will present a model that explains the variation in intensity based on the energy transfer coupling efficiency between the host semiconductor and the optically active erbium ions. The coupling efficiency is dominated by the alignment or misalignment of the erbium energy levels with the energy bands of the host semiconductor and by the excess carrier lifetime in the host. The data and model, which are presented here for the first time, are consistent with our previous work on the effects of co-doping with Be or Si and with other workers' measurements of thermal quenching in rare earth doped semiconductors.
Luminescence Properties of Yb- and Nd- Implanted CdS
Authors: Alshawa A. K. , Lozykowski H. J. , Li T. , Brown I.
Published: March 2011

The photoluminescence (PL) and time resolved spectra of Nd- and Yb-implanted CdS samples are studied under pulsed and CW excitations using Ar+ ion laser for different excitation intensities and temperature (9 - 300 K). The samples were annealed under different conditions using the thermal-pulse method. For CdS:Nd, the PL spectra was recorded in the range 890-930 nm (transitions 4F3/2→4I9/2) and for CdS:Yb it was recorded in the range 985 - 1010 nm (transitions 2F5/2 →2F7/2). The Rise time and decay time were studied for both CdS:Nd and CdS:Yb at different emission lines as a function of temperature and excitation power.
Electrically Pumped Rare Earth Doped Semiconductor Lasers
Authors: Pankove Jacques I. , Feuerstein Robert J.
Published: March 2011

The interest in rare earth (RE) elements as luminescent centers is due to the narrowness and stability of the luminescent transitions. In this paper we review the mechanisms that can be used to electrically excite rare earth impurities in semiconductors: pair recombination energy exchange and impact excitation. The different means of providing energetic electrons for impact excitation are also discussed. We also propose a possible explanation for the temperature dependence of photoluminescence in silicon.
Novel Electronics Enabled by Rare Earth Arsenides Buried in III-V Semiconductors
Authors: Allen S. James , Brehmer Dan , PalmstrØm C.J.
Published: March 2011

Heterostructures consisting of III-V semiconductors and epitaxial layers of the rare earth monoarsenides can be grown by molecular beam epitaxy. By alloying ErAs with ScAs, lattice match can be achieved with (Al,Ga)As. Using magneto-transport measurements, we show that these layers are semi-metallic with equal electron and hole concentrations, 3.0 ×1020 cm−3. Shubnikov-de Haas oscillations are used to confirm the predicted Fermi surface geometry and measure the electron effective mass and the coupling to the 4f spin on the Er3+ ion. Remarkably, the material shows no transition from semimetal to semiconductor as the film thickness is reduced to three monolayers. Below three monolayers the films are not uniform and are believed to consist of islands three monolayers high.

This system provides a unique opportunity to explore novel electronics based on controlled transport through semimetal/semiconductor heterostructures. Lateral transport through semimetal islands immersed in a δ-doped layer may provide a fast non-linear material for THz electronics. Vertical transport through thin epitaxial layers may enable resonant tunneling hot electron transistors with a semi-metal base. Preliminary experiments on transistor like test structures measure some transfer through a 10 monolayer thick semimetal base. They also identify overgrowth of the III-V semiconductor on the semimetal layer as the key materials issue.
Study of Srl−xErxF2+x Luminescent Thin Films Epitaxially Grown on InP (100).
Authors: Barriere A.S. , Mombelli B. , Kim B.Y. , Raoux S. , Garcia A.
Published: March 2011

Erbium-substituted Srl-xErxF2+x strontium fluoride layers were grown on InP(100) substrates by sublimation under ultra-high vacuum of high purity solid solution powders.

Their composition and the spatial distribution of the basic components were deduced from Rutherford backscattering (RBS), using a nuclear microprobe, and secondary ion mass spectrometry (SIMS). For x lower than 20% it is shown that the film composition is analogous with the initial sintered material and quite homogeneous. The ageing in air of the films was followed by infrared absorption studies. No significant water adsorption was revealed.

The texture of the layers was studied by RBS in channelling condition. For x as high as 15% it is shown that the films are well crystallized and well epitaxially grown on InP (100) substrates.

Infrared emission due to the 4I13/2-4I15/2 electronic transition on the 4f11 inner shells of Er3+ ions (1.53μm), which presents potential applications for optical communications, was studied at room temperature as a function of x. It is demonstrated that the highest luminescence efficiency of these layers corresponds to x upper than 20%.
Optical and Structural Properties of CaF2:Nd Films on Si-Based Substrates
Authors: Cho C.-C. , Duncan W.M. , Liu H.-Y.
Published: March 2011

By thermally evaporating CaF2 and NdF3, we have grown Nd-doped CaF2 films on Si(111), A1/Si(111) and quarter-wavelength Ta2O5/SiO2 multilayer Bragg reflectors. The optical and structural properties of the CaF2:Nd films are characterized by photoluminescence spectroscopy (PL) and x-ray diffraction. The effects of different Nd concentration, growth temperatures and post-annealing were studied. Regardless of the substrates, the as-grown films show emission lines at wavelengths similar to bulk CaF2:Nd. Annealing the films at 700°C in forming gas results in a new emission pattern. Little difference between the PL spectra of polycrystalline and single crystal CaF2:Nd films is observed, indicating that the luminescence efficiency is insensitive to the crystalline quality of the films.
Mbe Growth of Rare-Earth Doped Fluoride Insulators on Semiconductors for Laser Applications
Authors: Lui M. , Mcfarlane R.A. , Yap D.
Published: March 2011

With the recent success of using rare-earth doped fluoride crystals as high power visible upconversion lasers, we have explored the use of MBE grown fluoride layers for a possible waveguide laser. By confining the pumped light in a waveguide with dimensions on the order of a few micron, the pump power density will increase promoting higher efficiencies at room temperatures. Initially, we have grown planar waveguides of erbium doped ZnF2 on MgF2 substrates using molecular beam epitaxy and have formed channel waveguides by ion milling. By exciting individual channels with an 800 nm pump, we have generated strong upconversion fluorescence at 410 nm, 550 nm and 670 nm and at numerous weaker peaks. The fabrication techniques can be adapted to semiconductor substrates for making compact diode-pumped visible and infrared lasers. A number of fluoride materials that are useful as laser host crystals are lattice matched to GaAs (100) and GaAs (111) offering the possibility of integrating the channel waveguide laser with the semiconductor diode laser pump source. For example SrF2 may be grown on GaAs (100) as a cladding layer followed by PbF2 doped with a rare-earth ion. Also LaF3 may be grown on GaAs (111) followed by CeF3 doped with a rare-earth ion. Both PbF2 and CeF3 have low phonon energies and a higher index of refraction than their respective lattice matched cladding layers and should be capable of provide an attractive upconversion laser waveguide system. Our initial upconversion luminescence results on erbium doped PbF2 on GaAs (100) using a intervening SrF2 cladding layer are also reported.
Er-Doped GaAs for High Speed Photoconductor Applications
Authors: Gupta S. , Sethi S. , Bhattacharya P. K. , Williamson S.
Published: March 2011

The observation of 1.54 μm luminescence in erbium-doped-GaAs (GaAs:Er) and AlxGal-xAs, has stimulated research efforts because of their potential application to light sources in optical communications. In this paper, we study a different aspect of the photoresponse behavior of this material. The dependence of the carrier lifetime on the doping concentration of Erbium is investigated in GaAs:Er grown by MBE. A reduction in the carrier lifetime down to ∼1 ps is observed for the highest doping (∼5×1019 cm−3) investigated. Together with the high-resistivity observed for the higher doping values, this material serves as a novel photoconductor material for high-speed optoelectronics.
Effects of Microstructure on Photoluminescence of SrS:Eu2+,SM3+ thin Films
Authors: Hua Susan Z. , Salamanca-Riba L. , Wuttig M. , Soltani P. K.
Published: March 2011

The microstructure and its effects on the photoluminescence properties of SrS:Eu2+,Sm3+ thin films grown with different conditions were studied by transmission electron microscopy, x-ray diffraction and photoluminescence techniques. The SrS:Eu2+,Sm3+ thin films were prepared by e-beam evaporation at different substrate temperatures and growth rates. Both of these growth conditions affect the crystallinity of the thin films. The Sm3+ emission is stronger in the films grown at higher growth rates and at an optimum substrate temperature. We believe that the stronger Sm3+ emission is due to the higher population of Sm trivalent charge states in the films. Further increase of the substrate temperature increases the grain size in the films, but has no significant effect on the PL emission properties. In contrast, the Eu2+ emission is less sensitive to growth conditions.
Microelectronic Devices : Prospects for Rare-Earths
Authors: Zakharenkov Leo , Golubev Valeri , Kozlovskii Vitali
Published: March 2011

The report submitted contributes to the series of research works in the spheres of rare-earth (RE) application to electronic industry, and namely, to the production of such devices as surface-barrier structures, solar cells’ elements.
Rare-Earth Doping by Ion Implantation and Related Techniques
Authors: Brown Ian G.
Published: March 2011

Some metal plasma techniques have been developed that provide a convenient means for the doping of semiconductor hosts with rare-earths. These plasma and ion beam tools are based on the application of vacuum arc discharges for the formation of dense rare-earth plasmas which then can be used in a number of ways for doping and otherwise introducing the rare-earths into substrate materials. At the low energy end of the spectrum, the streaming metal plasma can be used for the deposition of thin films, and if more than one plasma source is used then of multilayer structures also. Or by building the vacuum-arc rare-earth plasma generator into an ion source configuration, high current ion beams can be produced for doing high energy ion implantation; alternatively the substrate can be immersed in the streaming rare-earth plasma and by using appropriately phased high voltage substrate pulsing and pulsed plasma generation, plasma immersion ion implantation can be done. Between these two limiting techniques – low energy plasma deposition and high energy ion implantation – a spectrum of hybrid methods can be utilized for rare earth doping. We've made a number of plasma and ion sources of this kind, and we've doped a wide range of substrates with a wide range of rare-earths. For example we've implanted species including Sc, Y, La, Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er and Yb into host materials including Si, GaAs, InP and more. The implantation dose can range from a low of about 1013 cm−2 up to as high as about 1017 cm−2, and the ion energy can be varied from a few tens of eV up to about 200 keV. Here we review these vacuum-arc-based plasma methods for rare-earth doping, describing both the tools and techniques that are available and the applications to which we've put the methods in our laboratory.
Er-Doping in Silicon by Pulsed Laser Irradiation
Authors: Nakashima Kenshiro
Published: March 2011

Erbium ions were successfully doped in silicon by pulsed laser irradiation above the threshold laser energy density. Photoluminescence peaks at 1.54, 1.59 and 1.64 µm from Er-optical centers were observed after annealing of Er-doped samples. The intensity of the 1.54 µm Er-emission band increased upon increase in the laser energy density, and then gradually decreased after reaching the maximum, due to the laser sputtering of the silicon substrate. Oxygen atoms, which were unintentionally codoped with Er-ions, were found to be distributed in the same region as in Er-ions, and were suggested to play roles to activate Er-optical centers. The maximum concentration of Er-ions doped in the solid state regime were estimated to be the order of 1018 cm−3 by the Rutherford backscattering measurements.
Oxygen-Enhanced 1.54µm Photoluminescence of Er+3 In Silicon
Authors: D'avitaya F. Arnaud , Campidelli Y. , Chroboczek J.A. , Favennec P.N. , L'haridon H. , Moutonnet D. , Wasiela A.
Published: March 2011

Favennec et al. (Jap. J. Appl. Phys. 29, L524, 1990) reported that the 1.54µm photoluminescence of Si implanted with Er+3 is activated by oxygen impurities. We observe a significant enhancement in the luminescence in Er-doped silicon epitaxial layers MBE-grown with intentional oxygen contamination. The PL is shown to be a bulk property of the material as it persisted after a partial layer removal by wet etching.
Modelling Electromigration and Induced Stresses In Aluminum Lines
Authors: Kirchheim R.
Published: March 2011

The various equations used by different authors for describing electromigration are compiled. All of them can be derived from a general equation which is based on a vacancy model. During the derivation of simplified versions of the general equations assumptions have to be made and their effect on concentration profiles and/or electromigration stresses developing as a function of time are discussed. Consequences with respect to Blech's experiment or the current exponent in Black's equation are taken into consideration and a simple explanation is provided for the beneficial effect of a (111) texture on the reliability of Al-lines.
Electromigration Damage in Fine Al Alloy Lines due To Interfacial Diffusion
Authors: Hu C-K. , Small M.B. , Rodbell K.P. , Stanis C. , Mazzeo N. , Blauner P. , Rosenberg R. , Ho P.S.
Published: March 2011

Both electromigration lifetime experiments and experiments of the drift velocity type have been conducted with the alloys: Al(2% Cu), Al(O.5% Cu,O.3% Zr), and Al(0.3% Pd,O.3% Nb) also with structures with two wiring levels of Ti/Al(0.5 - 4 % Cu)/Ti interconnected with W studs. The latter structure and these structures in general, are representative of present applications, which contain Al alloy/W interfaces. In all cases it was found that the mass transport along the line's edges played a role in their damage formation, which was at least as great as grain boundary diffusion. It is postulated that the results obtained using the traditional test structure, which has reservoirs of metal alloy at each electrode and is conducted at a single level, have been misinterpreted as indicating that flux divergence at triple junctions were critical failure sites for on-chip interconnections. These present results show that the material in the electrode pads of the conventional structure can resupply material to the lines. A direct experimental comparison of the two structural types is made to demonstrate the point.
The Effect of Thermally Induced Stresses on Electromigration Lifetime Of Near-Bamboo Interconnects
Authors: Korhonen M.A. , BØrgesen P. , Brown D.D. , Li Che-Yu
Published: March 2011

Thermal stresses may affect significantly electromigration induced open failures in nearbamboo interconnect structures ending in W-vias. Based on a physical model, we investigate the thermal stress effects on void nucleation, on early failures due to grain boundary diffusion, and on longer term bulk diffusion dominated failures. It is shown that thermal stress is all important as far as early failures are concerned. In particular, during accelerated tests and service, the early failures, when occur, arise due to stress and current directed grain boundary diffusion along grain clusters. In the accelerated test, bulk diffusion dominated void growth at vias determines the long term failures while during service bulk diffusion contribution is usually negligibly small within time frames of practical interest. Because the dominant failure mechanisms change, the extrapolation from the accelerated tests to the service conditions is not straight-forward.
Microstructural Mechanism of Electromigration Failure In Narrow Interconnects
Authors: Kim Choongun , Selister S. I. , Morris J. W.
Published: March 2011

Microstructural studies of electromigration failure were performed on A1-2Cu-1Si interconnects with 1.3 μm width. The lines were tested to failure under controlled conditions after pre-aging for various times at three different temperatures. Examination of the microstructure of the failure sites suggests that the lines fail at the bamboo grains that terminate the longest polygranular segments in the line. Transgranular slit voids form after Cu has been swept from the grain that fails. Hence, pre-aging lines to create a more stable distribution of Cu lengthens the time required to sweep Cu and significantly increases the time to failure. The optimal microstructure has a maximum intragranular density of stable θ precipitates. In this case transgranular slit failure is suppressed, and the bamboo grain fails by diffuse thinning to rupture.
Evidence of The Electromigration Short-Length Effect in Aluminum-Based Metallurgy With Tungsten Diffusion Barriers
Authors: Filippi Ronald G. , Biery Glenn A. , Wood Michael H.
Published: March 2011

Several phenomena related to the short-length effect were observed during lifetime measurements of a two-level structure consisting of Ti-AICu-Ti stripes connected by interlevel tungsten (W) stud-vias. A linear increase in resistance was followed by a resistance change with time that approached zero. The threshold product is not a constant at 250 °C for stripe lengths of 30, 50 and 100 μm. The sigma of the lognormal distribution increased as the current density decreased and/or as the fail criterion increased. The lifetime, or t50, at relatively small current densities did not obey Black's empirical equation. Rather, the lifetime data obeyed a modified version of this equation that includes a critical current density, jc, as a new parameter. This critical current density is strongly dependent on the fail criterion, but is independent of temperature in the range 210-250 °C.
On the Interface Properties and Deep Level Defects in Ta2O5 Grown on Si by Plasma Enhanced Liquid Source-Cvd
Authors: Murawala P.A. , Sawai N. , Tatsuta T. , Tsuji O. , Fujita Sz. , Fujita Sg.
Published: March 2011

We report, for the first time, on interface properties of the Ta2O5-Si system and on the deep level defects in Ta2O5 grown by plasma enhanced liquid source chemical vapor deposition (PE-LS-CVD) using Ta(OC2Hs)5. The capacitance voltage (C–V) measurement performed on Au/Ta2O5/n, p-Si MOS diodes resulted in very well defined C-V charactristics which compares well with the ideal C-V curve. The flat band voltage is as low as 0.15 V and the minimum density of the interface state is about 2.7 × 1011 cm−2 ev−1. In order to examine deep level defects in Ta2O5, we investigated variations of flat band voltage under application of high stress electric field (10MV/cm), by which hot carriers are injected in to deep levels. This charge transfer process results in increase of charges in Ta2O5 oxide which is attributed to the equivalent deep level defect densities, which is found to be of the order of 2 × 1011 cm−2 in the Ta2O5-Si system. These results strongly suggest low interface states and deep levels in the PE-LS-CVD grown Ta2O5-Si system, which may be brought about by low decomposed-carbon impurities in the film, confirmed by AES in our previous reports. These films can play a vital role as thin capacitors in I.C. technology.
Stress-Induced Voiding Vs Temperature and Passivation Thickness IN AI-0.5%Cu-2%Si, AI-0.5%Cu AND Al-i%Si
Authors: Sullivan T. D. , Miller L. A.
Published: March 2011

Stress-induced voiding in microelectronics chips has been reported to exhibit a variety of dependencies on temperature and on passivation stress. The dependence of line failure is reported here at four different temperatures (150, 225, 285, and 315 °C) for AI-0.5%Cu-2%Si, AI-0.5%Cu and AI-1%Si lines with passivation thicknesses (silicon oxide or silicon nitride) ranging from 0.1 to 2.5 times the metal thickness. Failure distributions change in a complex manner with changing passivation thickness, and with temperature for a specific passivation thickness, raising questions on the validity of using the conventional median time to failure (t50) and lognormal slope (σ) to project field failure rates from data generated by accelerated life testing.
Strain Relaxation and In-Situ Observation of Voiding in Passivated Aluminum alloy Lines
Authors: Besser Paul R. , Marieb Thomas N. , Bravman John C.
Published: March 2011

Strain relaxation in passivated Al-0.5% Cu lines was measured using X-ray diffraction coupled with in-situ observation of the formation and growth of stress induced voids. Samples of 1 μm thick Al-0.5% Cu lines passivated with Si3N4 were heated to 380°C, then cooled and held at 150°C. During the test, principal strains along the length, width, and height of the line were determined using a grazing incidence x-ray geometry. From these measurements the hydrostatic strain in the metal was calculated and strain relaxation was observed. The thermal cycle was duplicated in a high voltage scanning transmission electron microscope equipped with a backscattered electron detector. The 1.25 μm wide lines were seen to have initial stress voids. Upon heating these voids reduced in size until no longer observable. Once the samples were cooled to 150°C, voids reappeared and grew. The measured strain relaxation is discussed in terms of void and θ-phase (Al2Cu) formation.
Mechanical Stress Effects on Electromigration Voiding in a Meandering Test Stripe
Authors: Lowry Lynn E. , Tai Beverly H. , Mattila J. , Walsh LH.
Published: March 2011

Earlier experimental findings concluded that electromigration voids in these meandering stripe test structures were not randomly distributed and that void nucleation frequently occurred sub-surface at the metal/thermal oxide interface. The data showed a strong correlation between void area, void growth rate and stripe segment length [1]. The influence of mechanical stress on electromigration damage in these test structures has been examined by applying tensile stresses to both passivated and unpassivated samples. The stress distributions are calculated using finite element analysis for each of the test conditions. The resulting impact on electrornigration voiding, as well as mechanical stress voiding, and lateral hillock formation is discussed.
A Calorimetric Evaluation of Peel Adhesion
Authors: Farris Richard. J. , Goldfarb Jay. L.
Published: March 2011

Peeling of flexible poly(ethylene terephthalate), PET, and elastic steel films, adhesively bonded with a pressure sensitive adhesive layer, was analyzed from a thermodynamic perspective with the intent of determining how the energy expended in separating the bonded materials is consumed. The mechanical work expended and the heat dissipated during peeling were simultaneously measured using deformation calorimetry. For the PET backing material, which has a demonstrated capacity to store deformation energy as latent internal energy, most, but not all, of the peel energy was dissipated as heat. When perfectly elastic steel films were peeled, all of the peel energy was dissipated as heat, proving that no latent internal energy is stored in the adhesive layer during peeling and suggesting that the internal energy change of peeling adhesive backed with PET film was stored as latent internal energy in the PET backing. The stored latent internal energy in the peeled PET was measured using solution calorimetry. The thermodynamics of tensile drawing for PET was studied using deformation calorimetry, solution calorimetry, differential scanning calorimetry and thermomechanical analysis.
Non-Destructive Evaluation of Strains and Voiding in Passivated copper Metallizations
Authors: Vinci Richard P. , Marieb Thomas N. , Bravman John C.
Published: March 2011

Stress induced voiding in passivated Cu lines was investigated by x-ray strain analysis and in-situ high voltage scanning electron microscope (HVSEM) techniques. Cu lines on a Ta underlayer and Cu lines on an Al underlayer were patterned by a trilayer liftoff technique and passivated with Si3N4. For direct observation of stress voiding, specimens were heated to 350°C in the HVSEM and then cooled and held at 150°C. Identical samples were subjected to the same thermal cycle for strain state determination using x-ray techniques. The hydrostatic stress state at each temperature was calculated from the measured strains. Few initial voids were observed after passivation in either sample. After heating to 350°C and cooling to the dwell temperature, no new voiding was seen in the Ta/Cu lines. Measured hydrostatic strains were half those measured in the Al/Cu lines. Heavy voiding was observed in the Al/Cu lines after cooling to the dwell temperature.
Grain Boundary Sliding in Thin Substrate-Bonded al Films
Authors: Prieler M. , Bohn H.G. , Schilling W. , Trinkaus H.
Published: March 2011

A systematic investigation of the anelastic relaxation of thin Al films on Si substrates has been carried out. It was found that both the relaxation in bulk and thin film material can be explained by a model involving glide of grain boundaries (GBs). The mass transport necessary for the glide occurs via GB diffusion in the thin films and via lattice diffusion in the bulk material the different behavior being due to the more of two orders of magnitude smaller grains in the films. Internal friction thus provides a technique to measure diffusional parameters of GB diffusion in thin films.
Dispersion Strengthening of Al Films by Oxygen Ion Implantation
Authors: Bader S. , Flinn P.A. , Arzt E. , Nix W.D.
Published: March 2011

Finely dispersed, stable Al-oxide particles were produced in Al films on Si substrates by oxygen ion implantation. A laser reflow technique was employed to vary the grain structure of some of the films. Transmission electron microscopy (TEM) was used to characterize the oxide particles and the grain size in the films, and a wafer curvature technique was employed to study the influence of microstructure on the deformation properties as a function of temperature.

For coarse grained laser reflowed films, ion implantation increased the strength considerably, both in compression and in tension. Weak beam TEM techniques showed that the strengthening is most likely caused by attractive interactions between dislocations and particles. As-deposited and ion implanted films showed a stable grain size of only 0.35 μm after annealing, which caused significant softening to occur in compression, especially at high temperature. However these films showed very high stresses in tension at temperatures below 130°C. In these films the presence of the oxide particles stabilizes the small grain size and this causes a weakening effect which can be attributed to diffusion controlled grain boundary relaxation mechanisms. The high tensile stresses at temperatures below 130°C can be explained by direct and indirect particle strengthening.
Effects of Confinement on Plastic Deformation in Passivated Al Films
Authors: Anderson S.G.H. , Yeo I.-S. , Ho P.S. , Ramaswami S. , Cheung R.
Published: March 2011

Wafer curvature measurements of a trilayer (SiO2 / AlSiCu / Si) structure are compared to that predicted by a weighted sum of individual measurements of SiO2 and AISiCu films on Si, and significant differences are found to exist for temperatures above 200°C. A straightforward analysis of the stresses in each layer has been modeled using an extension of a model by Feng et al. which assumes uniform plastic deformation throughout the Al. The modeling results suggest a straightforeward method for determining stresses in deformable thin films that are confined by elastic overlayers. A comparison of the stress-temperature behavior for unpassivated and passivated AISiCu films reveals that the confined films exhibit less plastic deformation and both higher tension and compression during thermal cycling.
The Influence of Mechanical Stress on Hot-Carrier Degradation in Mosfet's
Authors: Wolf Ingrid De , Bellens Rudi , Groeseneken Guido , Maes Herman E.
Published: March 2011

Non-uniform hot-carrier degradation in n-channel polycide-gate MOSFET's with different thicknesses of the poly-Si film, and in p-channel polycide-gate MOSFET's with TiSi2- or CoSi2-gate-silicide, is studied. The n-MOSFET's with the thinnest poly-Si film, show an increased interface trap generation, while the influence of the gate-silicide material on the degradation behaviour of the p-MOSFET's is found to be very small. The results are evaluated in terms of the effect of mechanical stress on the degradation characteristics: favourable for compressive mechanical stress and unfavourable for tensile stress. A correlation with stress measurements by micro-Raman spectroscopy is made.
Temperature Dependence of the l/f Noise in Heat-Treated Films of Al And Al-Cu
Authors: Biery Glenn A. , Smith Richard G. , Ficalora Peter J.
Published: March 2011

The 1/f noise in heat-treated Al and AI-Cu thin films was investigated at a current density of 20 mA/μm2 from approximately RT to 200 C. The results were consistent with the Dutta-Dimon-Hom model, i.e., the noise is the result of a collection of two-state systems. From the temperature dependence of the noise, a modified Dutta-Dimon-Hom model was used to extract the energy of formation, ΔHf, and the energy of migration, ΔHm, of the noise process. The development as well as simulations of this model will be discussed. It will be shown that ΔHm can be determined through investigation of the temperature at which the noise magnitude peaks for many frequencies. It will also be shown that ΔHf can be determined by investigation of the temperature at which the noise magnitude peaks and the temperature at which a, the negative of the logarithmic slope of the power spectral density, passes through 1. For both the Al and Al-Cu films, ΔHm was approximately 0.7 eV. The results also indicated that ΔHf was ≤ 0.1 eV for the Al films, and only slightly higher, i.e., 0.1 - 0.2 eV, for the Al-Cu films. The temperature at which cx passes through I was similar for both the Al and AI-Cu films. These results strongly suggest that the l/f noise is caused by the motion of Al atoms along the grain boundaries.
Modeling 1/f noise using a simple physical model based on vacancy motion
Authors: Klonais N. S. , Cottle J. G.
Published: March 2011

A computer model is presented and used to simulate the motion of vacancies in a crystalline lattice. The lattice is modeled as a resistive array connected in series/parallel with vacancies represented as elements of high resistance in the array. Time series and spectra are generated by allowing the vacancies to move and these are consistent with actual waveforms produced by thin metal films. Simulation of temperature change yields dependencies similar to those predicted by Dutta and Horn (1979). By varying the density of vacancies the model predicts a variable Hooge parameter that saturates to a constant beyond a critical value.
The Finite Electromigration Boundary Value Problem
Authors: Lloyd J.R. , Kitchin J.
Published: March 2011

The solution to the finite electromigration boundary value problem has been obtained for the case of a blocking boundary downstream and a constant vacancy concentration upstream. The results are similar to the solution to the semi-infinite problem [1] except in the vicinity of the steady state. Consequences of achieving a “sub-threshold” steady state profile are discussed.
Evolution of Electromigration-Induced Voids in Single Crystalline Aluminum Lines with Different Crystallographic Orientations
Authors: Joo Young-Chang , Thompson Carl V.
Published: March 2011

Transgranular slit-like voiding has been observed to cause fatal defects in electromigration- or stress migration-damaged Al submicron interconnects. To study the morphology and crystallographic characteristics of transgranular voids, we have tested single crystalline Al lines with various textures and in-plane orientations. Lines with (100), (110), and (111) textures were found to have triangular erosion voids along their edges. These voids were generally bound by {111} facets. While triangular erosion voids are frequently found in the lines, not all lead to failure of the lines. Some lines fail due to narrow, slit-like voids which are bound by {111} planes and lie along either <110> or <112> in-plane directions, depending on the orientations of the crystals relative to the orientations of the lines. Some of the slit-like voids are initiated along the erosion void facets. Similar void morphologies are observed in both unpassivated and passivated lines. Some of the lines have very large voids at the negative pad implying that voids are mobile. Through continued studies of the failure rates and failure morphologies of single crystalline lines, the mechanisms of transgranular failure of polycrystalline lines should be clarified.
Reliability Issues of a Crack-Resistant Passivation Layer Process for Sub-Micron Non-Volatile Memory Technology
Authors: Moinpour Mansour , Chu John , Lubic Karen , Moghadam Farhad
Published: March 2011

Chemically vapor deposited phosphosilicate glass (PSG) has been used extensively for final passivation on EPROM and other Non Volatile Memory (NVM) technologies. The maximum amount of phosphorous that can be added to the passivation oxide (post metallization) is constrained by the stability of the as-deposited, undensified film. Atmosphericpressure chemically vapor deposited films of various dopant levels ranging from pure PSG to various boron and phosphorous wt%BPSG films were studied with respect to their passivation properties. The film performance with respect to passivation crack resistance, step coverage, and impacts on metal cracks/voids was evaluated. It was found that the crack resistance was by far more sensitive to boron concentration than that of phosphorous in the undensified film. The crack resistance is shown to be dependent on the as-deposited film densities, moisture levels and amount of shrinkage after a 400° C alloy/anneal. Other important parameters such as stress levels, UV transparency and sodium gettering capabilities were investigated. Reliability data on packaged-device level testing (both ceramic and plastic units) are also presented.
Iron Redistribution in Aluminum Thin Films
Authors: Barr David L. , Gualtieri G.J. , Case C.B. , Marcus M.A. , Brown W.L.
Published: March 2011

Strongly non uniform Fe depth distributions have been observed in AI(0.13 at% Fe) thin films deposited at temperatures of 350ºC and above. The concentration of Fe is uniform in depth at a deposition temperature of 300ºC but is increasingly enhanced toward the substrate interface at 450ºC. Subsequent annealing produces only a slight redistribution of Fe. The Fe is primarily present as precipitates smaller than 100 nm. A model of grain boundary diffusion of Fe and precipitate formation and grain growth is proposed to explain the observed behavior.
A Fresh Insight into Film Morphology Measurement Techniques for Advanced Ulsi Manufacturing
Authors: Ramaswami Seshadri
Published: March 2011

A laser based non-destructive technique has been used to study the morphology of sputterdeposited aluminum alloy films. The data emanating from the Therma-wave Imager that makes use of this principle, has been correlated with reflectivity, grain size and micro-roughness of the film. In addition, through the use of a case study, this paper demonstrates the utility of this application as an in-line monitor in an integrated circuit fabrication line.
Observation of Reduced Oxidation Rates for Plasmaassisted CVD Copper Films
Authors: Ding P. J. , Zheng B. , Eisenbraun E. T. , Lanford W. A. , Kaloyeros A. E. , Hymes S. , Murarka S. P.
Published: March 2011

Oxidation kinetics of plasma-assisted chemical vapor deposited (PA-CVD) copper films were investigated using Rutherford backscattering spectrometry (RBS). The PA-CVD copper films were deposited using hydrogen plasma reduction of bis(hexafluoroacetylacetonato) copper(II), Cu(hfa)2, precursor. Under identical experimental conditions, PA-CVD copper films oxidize more slowly than sputtered copper films. This decrease in oxidationis manifested both as a time delay at the beginning of the oxidation of the PA-CVD copper films and as a decrease in the rate of oxide growth at oxidation temperatures of 200ºC and below. The possivation appears to be caused by the hydrogen plasma present during depostion.
In Situ Xps Studies of the Deposition of Thin Films from Tetrakis(Dimethylamido)Titaniumorganometaluc Precursor for Diffusion Barriers
Authors: Ruhl G. , Rehmet R. , Knoživá M. , Vepřek S.
Published: March 2011

With the decreasing minimum feature size of integrated microcircuits, a low-temperature, chlorine-free CVD process is needed for the deposition of TiN diffusion barriers. A problem during the thermal deposition of titanium nitride from organometallic precursors, such as tetrakis(dimethylamido)titanium, is the high content of carbon in the films. In situ XPS study reveals that most of the carbon is present as CHx inclusions with a smaller but not negligible amount of carbidic component. This can be avoided by using ammonia, but the high rate of the reaction in the gas phase makes the control of the film growth difficult. Most of the problems can be resolved when using hydrogen afterglow.
Stability of Silicide Films Under Post-Annealing: a Dopant Effect
Authors: Shepard C.L. , Lanford W.A. , Pant A.K. , Murarka S. P.
Published: March 2011

The formation of PtSi films by rapid thermal processing of e-beam evaporated Pt on <100> Si has been studied. The current study found that PtSi films have the potentially useful property of oxidizing, i.e., forming a surface layer of Si02 which may be useful for patterning. Rapid oxide formation is found with, possibly, linear growth rates when the film is doped with As to 8E15 atoms/cm2 at 80 KeV but insignificant oxidation if the film is undoped or B-doped. Rutherford backscattering analysis shows significant redistribution of the As during silicidation and oxidation with As excluded from the silicide, diffusing to the oxide and especially the oxide surface. Post-silicidation anneals have been done in a conventional tube furnace at 650ºC for up to 60 minutes and form an oxide thickness of up to 200 nm. NiSi films appear stable if Bdoped, oxidize with Ni piling up at the Si02/Si interface if undoped, and are unstable with Ni diffusing deep into the Si if As-doped.
Amorphous Carbon as a Diffusion Barrier to Copper
Authors: Purser Richard G. , Strane Jay W. , Mayer James W.
Published: March 2011

Amorphous carbon was evaluated as a diffusion barrier between Cu and Si. Samples were annealed at 500 ºC for 1 hour in vacuum. Barrier properties were characterized for metallurgical failure with RBS and XTEM, and electrical properties were characterized with pn junction diodes and MOS capacitors. RBS and X-TEM showed that a barrier 13.5 nm thick prevented Cu and Si diffusion during the anneal. The diodes remained rectifying after annealing, although the series resistance went up. C-V measurements of the capacitors did not show the hysteresis that is typical of mobile charge in the oxide. The barrier breakdown mechanism is diffusion through the amorphous structure.
Oxide Degradation Resulting from Photoresist Ashing
Authors: Mikulan P. I. , Koo T. T. , Awadelkarim O. O. , Fonash S. J. , Ta T. , Chan Y. D.
Published: March 2011

In this study, possible SiO2 damage that could result from several different photoresist ashing techniques has been assessed using patterned photoresist over blanket oxides. The types of ashing systems used were RF power (RF), upstream ozone generator (Upstream) and two microwave power reactors (Microwave 1 and Microwave 2). Aluminum capacitors were evaporated on the samples after the ashing for oxide evaluation. Electrical characterization of these MOS structures included capacitance verses voltage and time dependent dielectric breakdown measurements. We also looked for Si substrate damage in these samples using deep level transient spectroscopy and Schottky barrier current-voltage measurements. This characterization showed oxide damage varied widely with ashing tool. In all cases, however, there was no significant Si substrate damage.
The Role of Texture On The Reliability Of Aluminum Based Interconnects
Authors: Knorr David B.
Published: March 2011

Preferred crystallographic orientation has long been recognized to play an important role in interconnect reliability where a strong (111) texture improves electromigration lifetime. Detailed microstructural analyses have enabled the role of texture to be better understood. Although Bragg-Brentano scans are often used to characterize texture, it is shown that this technique gives incomplete and sometimes misleading information. The pole figure technique provides a complete description of the texture. The measurement and presentation of textures consider experimental aspects unique to thin film analysis as a prerequisite to developing quality data. Five textural archetypes are identified, and metrics presented for their quantification. Processing effects on texture are complex and depend on all facets of deposition conditions, on substrate/underlayers, and on annealing. General trends and specific examples of the impact of each aspect are given where it will be shown that deposition conditions and the presence of underlayers have the greatest influence. The role of texture on reliability is considered for four failure modes: thermal hillocks, grain collapse, stress voiding, and electromigration. Electromigration results are emphasized where texture must be considered in the context of grain structure, in general, and, more specifically, the ratio of line width to grain size. Most measures of microstructure and reliability are statistical. The importance of local microstructural analysis will be emphasized in terms of both the arrangement of grains relative to the line dimension and microtexture characterization of the grain-to-grain misorientations.