bluuebunny/crossref_metadata_2025 huggingface dataset:
Modification of Electronic Transport in Polymer and Carbon Films by High and Low Energy Ion Irradiation
Authors: Venkatesan T. , Levi R. , Banwell T. C. , Tombrello T. , Nicolet M. , Hamm R. , Meixner A. E.
Published: March 2011

We have explored the origin of the ion-induced conductivity in polymer films and the distinction between low energy ion-implantation and high-energy ion irradiation. In experiments involving irradiation of polymer and carbon films with ions of energy from 200 keV to 25 MeV we have established that with both low and high energy ions the polymers undergo carbonization. However, the saturation resistivity obtained with low energy implantation is four to six orders of magnitude larger than those obtained by high energy ion irradiation. In experiments on irradiation of carbon films low energy ions caused a two orders of magnitude increase in the resistivity while high energy ion caused a two orders of magnitude decrease. This implies that the structure of the carbonized polymer is different for the low and the high energy ion irradiation. While in the former case there may be no crystalline order in the films; in the latter case, a microcrystalline graphitic structure is obtained (with four orders of magnitude larger conductivity than in the former case). The formation of graphitic crystalline order with increasing high energy ion dose was verified by electron energy loss spectroscopy. This is an interesting example of crystallization induced by electronic excitation alone with no macroscopic thermal effect.
Dose Measurements on Micro- and Submicrometer Implanted Structures using Thermal-Waves
Authors: Smith W. Lee , Reuss Robert H. , Clark William , Rensch David
Published: March 2011

Thermal-wave measurement techniques have recently been developed for measuring ion implant dose over the range 1E10 to 1E16 ions/cm2. The spatial resolution obtained with this method is 1 µm, an improvement of approximately 3000X over that of other dose monitors. This resolution capability together with the fact that the thermal-wave measurements are noncontact and nondestructive, permit dose measurements to be made on implanted areas (device features) on patterned wafers, as well as on test wafers.

A new potential application of the thermal-wave technique is the measurement of dose implanted by focused ion beam (FIB). Since the FIB technique is a high-resolution, direct-write process and since current FIB systems are limited to scan fields of less than 0.5 mm2, a high-resolution probe to monitor dose and uniformity is necessary.

In this paper, we report the measurement of ion dose implanted by focused beams into areas of ‹10−2 mm2. Even single FIB-implanted lines of 0.20 µm width have been detected, and programmed lateral dose variations measured. Experimental results demonstrating the potential of this technique are presented.
Chemical Metal Deposition on Insulators by An Ion-Beam Process
Authors: Eskildsen Svend Stensig , SØrensen Gunnar
Published: March 2011

An ion-induced decomposition of thin metal-compound films on insulating surfaces is described. 100-keV ion beams of Ar+, Kr+, and Xe+ was used to decompose thin (~10 nm) films of a palladium compound on polyimide and alumina. Changes in the stoichiometry have been observed with Rutherford Backscattering Spectrometry. The compound was also decomposed in a pattern using a mask, and the nondecomposed film could easily be removed with a suitable solvent. The decomposed palladium compound was used as a catalyst for a direct, electroless metal deposition of Cu. The plating speed was 30 nm/min, and a 4-5 µQcm copper film could be obtained after 3-4 min plating. Plated metal patterns are demonstrated on both polyimide and alumina, with a resolution in the µm range. On polyimide plating of a three-dimensional structure has been demonstrated.
Regrowth of Amorphized Compound Semiconductors
Authors: Opyd W.G. , Gibbons J.F.
Published: March 2011

Epitaxial regrowth is investigated for layers of InSb and GaAs amorphized by liquid nitrogen temperature ion implants. Experimental criterion for amorphization and limitation of regrowth are correlated with damage calculated by a Boltzmann transport equation approach to ion implant modeling. Conditions for complete epitaxial regrowth as determined by channeled Rutherford backscattering spectrometry are presented with evaluation of residual defects by transmission electron microscopy. Electrical activation following regrowth of GaAs is reported and correlated with calculated damage profiles.
Tem Structural Studies on Zn+ Implanted and As+ /Zn+ Dually Implanted GaAs
Authors: Morita E. , Kasahara J. , Arai M. , Kawado S.
Published: March 2011

Microdefects in Cr-doped SI LEC (001) GaAs wafers which were implanted with Zn+ or As /Zn and capless-annealed in an As ambient have been studied by means of transmission electron microscopy. Most of the microdefects in Zn +- implanted GaAs specimens were identified as precipitates and stacking fault tetrahedra (SFTs). Every SFT was accompanied by a precipitate at the apex. Most of the precipitates were distributed from Rp to Rp + 2∆Rp. Two types (α and β) of SFTs were differentiated by the arrangement of atoms in the core of the stair-rod partial dislocations bounding the periphery of the SFTs in a polar Frystal. β-SFTs were, however, predominantly formed in Zn+ implanted GaAs specimens. Dual implantation of As+ and Zn+ suppressed the formation of SFTs, but not that of precipitates. The formation of SFTs was found to be influenced by the deviation in stoichiometry.
Rapid Thermal Anneal and Furnace Anneal of Silicon and Beryimlum Implanted Gallium Arsenide
Authors: Yuen A.T. , Long S.I. , Merz J.L.
Published: March 2011

A comparison has been made between rapid thermal annealing (RTA) and furnace annealing (FA) of implanted GaAs. Hall measurements showed consistently higher electrical activation of n-type (Si-5E12 cm −2) implants with FA and higher electrical activation of p-type (Be-1E14 cm −2) implants with RTA. Photoluminescence (PL) revealed that for RTA temperatures above 950°C some of the Si was going onto As, acceptor sites, thus reducing the net donor concentration. PL for RTA below 950°C showed signs of incomplete recrystallization. By a technique of “dual implantation” of As and Si into GaAs we were able to force the Si onto Ga-sites resulting in a higher donor concentration after RTA.
Correlation of Rutherford Backscattering and Electrical Measurements on Si Implanted InP Following Rapid Thermal and Furnace Annealing
Authors: Bahir G. , Merz J.L. , Abelson J.R. , Sigmon T.W.
Published: March 2011

We report on the structural and electrical properties of (100) InP resulting from the implantation of 180 keV Si+ and subsequent annealing. The radiation damage produced by implantation at substrate temperatures from 77 to 480 K is evaluated using MeV He ion channeling. Varying degrees of recrystallization are found depending on the implant temperature and choice of furnace vs. rapid thermal annealing. Samples implanted at 25°C to a dose of 3.3.1014ions/cm2 continue to display structural disorder regardless of annealing procedures. In contrast, implantation at 200°C to 3.3-1014ions/cm2 produces a low but measurable damage level. Further annealing lowered the disorder to a level similar to that of unimplanted material.

The electrical activation of both low and high fluence ion doses is nearly the same at the optimal conditions for rapid thermal annealing (RTA) or furnace annealing (FA). However the electron mobility is found to be higher after hot implantation and RTA. The electrical profile after hot implantation is wider than the profile after RT implants and FA.
Buried Oxide in Silicon by Oxygen Implantation Into Scanned Wafers
Authors: Mogro-Campero A. , Love R.P. , Lewis N. , Hall E.L. , McConnell M.D.
Published: March 2011

A single crystal silicon layer on an insulator is a desirable structure for applications in electronics. One of the leading processes for achieving such a structure is the formation of a buried oxide layer in silicon by heavy dose oxygen implantation. Characteristics of this material have been reported for implantation by beam scanning. In this work we report on material prepared by wafer scanning at rates such that significant temperature cycling occurs during implantation, and we use TEM and Auger analysis to investigate the differences between these samples and others prepared by the conventional technique of beam scanning. For the implantation and annealing conditions used here, we find more oxygen in the top silicon layer in the case of wafer scanning, and the oxygen concentration increases after annealing at 1150°C for 2 hours, leading to a structure of precipitates throughout the single crystal top silicon layer. For beam scanning, the oxygen concentration decreases after annealing and achieves background levels near the surface, leading to a zone which is free of precipitates.
On The Formation of Si Oxide by Ion Implantation
Authors: Namavar F. , Budnick J.I. , Sanchez F.H. , Hayden H.C.
Published: March 2011

Oxygen 0+ ions have been implanted into Si both at room temperature and liquid nitrogen temperature in order to determine the effect of implantation temperature on SiO2 formation. Samples were analysed by RBS with 1.5 MeV He+ ions. The implants of 0+ in Si were done at 150 keV with current densities of ≤10 μA/cm2. For doses of more than 1.5×1018 0+/cm2, in-situ RBS experiments positively indicate a 2:1 oxygen silicon ratio. Increased 0+ doses (for both room temperature and liquid nitrogen temperature) cause the Si02 layers to spread uniformly and symmetrically toward both the surface and the interior. From these results, it is apparent that excess oxygen diffuses toward Si/Si02 interfaces in our experimental situation even at liquid nitrogen temperature.
Defect Structure at Buried Silicon Nitride Layers
Authors: Kaat E.H. Te , Belz J.
Published: March 2011

Buried insulating silicon nitride layers are formed by a 400°C N+-implantation at 150 keV with fluences from 0.35 to 1×1018 N+/cm2 and subsequent anneal at 1200°C in dry nitrogen. TEM and AES measurements on bevelled samples yield a correlation of ion and damage profiles to local defect structures. Low dose implantation results in polycrystalline precipitates of scaled spherulitic structure. High dose continuous polycrystalline nitride layers have good insulation properties following a 5 hour anneal. During anneal, the common asymmetrical ion depth profile transforms to a nearly rectangular profile. The silicon surface layer contains 106 to 108 dislocations/cm2, which seem to be passivated, since detrimental effects on electronic devices have not been measured.
Some Recent Developments in Industrial Ion Implanters
Authors: Ryding Geoff
Published: March 2011

semiconductor doping. This paper surveys some of the equipment developed at Eaton Corporation in response to the proliferation of ion implanted devices. Developments in both high current (~10mA) and medium current (~1mA) implanters will be discussed.

The evolution of dedicated equipment for the production of buried oxide layers (silicon on insulator technology) will also be reviewed.
The Channeling of Ions Near the Silicon 〈001〉 Axis
Authors: Ziegler J. F. , Lever R. F.
Published: March 2011

The first experimental mapping of the ion beam channels near the Si 〈001〉 axis is reported. Remarkably fine structure is observed, with over thirty microchannels identified within 20 degrees of the Si 〈001〉 axis. Each map is made from about 16000 channeling spectra with each channeling probability becoming a pixel of information in the final plot. Contour maps have been constructed for ions of He and N with energies from 50 to 2000 keV. All features are identified by theoretical plots of silicon planar channels and axial channels.
Effect of Preamorphization Depth on Channeling Tails in B+ and As+ Implanted Silicon
Authors: Suni I. , Rqnkainen H. , Eranen S. , Murto T. , Krontiras Ch. , Finetti M.
Published: March 2011

We have studied the effects of ion-channeling in B+ and As+ implanted Si which has been preamorphized to different depths by 28 Si+ irradiation at 60 keV and 180 keV. It is shown that the junctions for incompletely amorphized substrates are only slightly deeper than predicted by LSS theory. For preamorphized layers extending beyofnd-the predicted junction depths the implantations of 25 keV B+ and 120 keV 75As+ with a dose of 5-1015 cm-2 yield junction depths in the order of 2200 - 2300 Å after furnace annealing at 700°C for 30 minutes.
Electro-Optical Characteristics of Shallow Silicon Junctions Fabricated Through Masked Ion Implantation
Authors: Silard Andrei P.
Published: March 2011

The work presents the main electro-optical characteristics of very shallow silicon n+-p and P+-n junctions fabricated through masked ion implantation of phosphorus (31P+) and boron (11B+), respectively. The dependence of electro-optical characteristics on technological parameters (implant energy E and dose Q, oxide thickness Xox, impurity redistributions, etc.) are outlined in detail.

The implant step was performed through a thermally-grown silicon dioxide (SiO2) mask of variable thickness (Xox = 100-1200 Å) at energies ranging from E=10 keV to 50 keV and with a dose level Q = 5 x 1014 - 2 x 1015 cm-2. As a rule, after the implant step the oxide layer was etched down. In several samples, the Si0 2 layer was preserved in the finished devices.

The characterization of fabricated junctions was performed using a Karl Zeiss quartz prism monochromator coupled to a Tektronix 31/4661 data acquisition system. The main peculiar results could be summarized as follows: (a) all fabricated devices possess a relatively large bandwidth (up to 580 nm) of the relative spectral response; (b) for oxide thickness Xox Rp (projected range), the low energy implant yields devices with good blue response; (c) for Xox equal or larger than Rp a pronounced shift of the peak responsivity wavelength toward the visible spectrum of the light occurs; (d) a distinctive feature of devices consists in the high peak values of the short-circuit current density under AM1 insolation (in excess of 33 mA/cm2); (e) the preservation of SiO2 layer in the finished devices improves their electro-optical characteristics.
Regrowth of Implanted-Amorphous Si: Furnace to Laser Annealing
Authors: Mayer James W.
Published: March 2011

High-quality, epitaxial layers regrown from ion-implanted, amorphous Si are an important element in integrated circuit fabrication. Two regimes are well-characterized and understood: furnace annealing in the solid phase from 500° to 1000°C and pulsed-laser annealing in the liquid-phase. Growth rates have been measured in the range from 1 Å/sec in the solid phase to 10 m/sec in the liquid phase. Impurity redistribution is in hand and only the strong enhancement of solid phase rates due to the presence of 0.1 at. % or greater of dopants remains as a controversial issue.

The emergence of rapid thermal annealing (10 to 20 sec at 1000 to 1100°C) as an attractive method of restoring crystal order has introduced a new area of controversy; in this case, growth rates and impurity redistribution. The experimental data from several groups will be presented in order to highlight the different mechanisms that have been invoked. The redistribution of implanted B and As will also be discussed.
Interface and Bulk Oxide Damage Induced by Boron Implantation
Authors: Wong H. , Cheung N.W.
Published: March 2011

Investigations were carried out on the damage of SiO2 and the Si-SiO2 interface induced by boron implantation through polysilicon/SiO2 /p-Si structures with doses up to 1014cm−2 and annealed at 950°C. Using the constant voltage stressing technique, both capacitance-voltage and thin-oxide tunneling current measurements showed that both electron trapping and hole trapping are increased, and that ion-induced electron trapping overcompetes hole trapping for boron doses higher than 5×1013cm−2.
Magnetic Properties of Ions Implanted in Glass; Fe in SiO2
Authors: Weeks R.A. , Silva M.C. , Kordas G. , Kinser D.L. , Martinelli J. , Appleton B.R.
Published: March 2011

Silica glass platelets have been implanted with Fe(+) ions, 125 KeV and 10⋀-5 A to doses of 10⋀14 cm⋀-2, 10⋀15 cm⋀-2, 10⋀16 cm⋀-2 and 5 x 10⋀16 cm⋀-2. Ion scattering measurements show that the peak of the Fe ion distribution is ~95 nm below the sample surface, approximately Gaussian, with a width at half maximum amplitude of 100 nm. The intensity of a component in the EPR spectra of implanted samples with a width of 300 gauss and an approximately isotropic shape increases with increasing dose. The increase, proportional to dose for doses <⋀16 cm⋀-2, is larger for doses ≥10⋀16 cm⋀-2. In addition for doses ≥10⋀16 cm⋀-2, the component is orientation dependent. Subsequent heat treatments in air at 700° and 800° C alter the shape, intensity, and orientation dependence of the component. The spectral component in as-implanted samples is attributed to paramagnetic states of Fe ions. The threshold for magnetic exchange interactions and consequently long range magnetic ordering at ~300K occurs at a dose ≥10⋀16 cm⋀-2. Data on effects of thermal treatments on intensities and shapes are interpreted in terms of changing chemical composition of precipitating-particles.
The Formation of Amorphous Silicon by Light Ion Damage
Authors: Shih Y. , Washburn J. , Weber E.R. , Gronsky R.
Published: March 2011

A model for formation of amorphous silicon by light ion implantation is proposed. It is suggested that accumulation of point defects and/or complexes is required at the initial stage of the amorphization process. Amorphous zones can only form at the end of incoming light ion tracks when the pre-accumulated concentration of point defects reaches a critical value. Depending on the uniformity of the point defect distribution, two possibilities for the second stage of amorphization are suggested when ion implantation is performed at different temperatures.

Silicon wafers implanted with boron ions below and above the critical amorphization dose at various temperatures have been investigated using cross section specimens in high resolution TEM. Complementary analyses of these specimens by Electron Paramagnetic Resonance have revealed the presence of dangling bonds in amorphous zones and point defect clusters. Extrinsic stacking faults with 1/3 <111> displacements and other smaller distortions with 1/x<111> displacements were also found to result from the amorphization process. Liquid nitrogen temperature was found to be necessary to cause complete amorphization of silicon by boron ion implantation.
Rapid Thermal Processing (RTP) of Shallow Silicon Junctions
Authors: Seidel T.E.
Published: March 2011

Rapid Thermal Processing (RTP) is used to study shallow junction formation for high dose implanted silicon. The residual damage from As damage is efficiently removed using high temperature-short time anneals (1100°C - few seconds), while limited arsenic atom diffusion is obtained. The diffusion properties are also characterized by concentration enhanced diffusion at higher doping. The higher doping is metastable, with reversible changes in resistivity observed for sequential 1100°C-800°C-1100°C-800°C thermal cycles. RTP gives shallower defect free As junctions than standard long time anneals. Boron junctions are limited by the depth extension of a large ion-channeling-tail which is shown to undergo local enhanced diffusion. The approaches to form shallow p+ junctions without channel tails are discussed. A summary of ion damage studies is made. Some generalizations for determining an RTP advantage or disadvantage are made, based on activation energy differences of effects.
Electronic Stopping Power for Low Energy Ions
Authors: Azziz N. , Brannon K. W. , Srinivasan G. R.
Published: March 2011

A procedure to be used in ion implantation calculations has been developed to determine the stopping power of an ion at low energy as a function of its effective charge. The ion effective charge accounts for screening of the ion and has been found to have considerable effect on the stopping power through its dependence on the target electron density. Steps in the procedure include: the calculation of the Fermi momentum of the target, calculation of the relative velocity between the projectile and target electron cloud, determination of the screening distance for the ion, and calculation of the proton stopping power Sp according to the density-functional formalism. The ion stopping power is then is the ion effective charge. The procedure can be applied to semiconductors and metals. Comparisons are reported with the predictions of the Firsov and Lindhard methods which do not include any effective charge or shell structure considerations. The computer program MARLOWE has been modified to include this method for calculating the stopping power. Results in the form of implanted boron profiles in silicon will be presented.
The Entropy of Defects and Diffusion in Silicon
Authors: Bar-Yam Y. , Joannopoulos J. D.
Published: March 2011

Theoretical calculations of the finite temperature properties of defects, such as defect concentration and diffusion rate, require a knowledge of the entire 3N-dimensional defect total energy surface. We present a formalism for obtaining such defect energy surfaces from total energy calculations. Preliminary results of the application of this formalism to the silicon selfinterstitial are described. Implications for understanding the remarkable experimental high temperature diffusion entropies are discussed.
Electronic Structure of Mercury, Gold and Platinum Impurities in Silicon
Authors: Leite Jose R. , Alves Jose L.A.
Published: March 2011

The electronic structures of substitutional and tetrahedral-site interstitial Hg+, Auo and Pt− isoelectronic impurities in silicon have been analysed. The centers are theoretically described by the Watson-sphereterminated molecular cluster model within the framework of the multiplescattering Xa formalism. At the substitutional sites the centers are related to the “vacancy” model recently proposed to describe the properties of the elements at the end of the transition-metal series. At the interstitialsites the impurities introduce a hyperdeep s-like level close to the bottom of the valence band and, in agreement with experiments, do not show shallow donor activities. For all the analysed centers the d-states remain fully occupied below, or within, the valence band.
Photo-EPR and Spatially Resolved EPR of ASGa in As-Grown GaAs
Authors: Baeumler M. , Kaufmann U. , Windscheif J.
Published: March 2011

The photo-response of the ASGa+ antisite electron-paramagnetic-resonance (EPR) has been studied in as-grown GaAs as a function of illumination time and photon energy. The results establish a firm and positive correlation between ASGa and the deep donor level EL2. Spatially resolved EPR measurements show that the ASGa concentration can fluctuate by about a factor of two across a 2-inch semiinsulating GaAs wafer.
High Resolution Optical Study of The Antisite Defect ASGa in GaAs; Correlation with Midgap Level EL2
Authors: Skowronski M. , Lin D.G. , Lagowski J. , Pawlowicz L.M. , Ko K.Y. , Gatos H.C.
Published: March 2011

A high resolution optical study was carried out on GaAs crystals containing only the EL2 midgap level. The no-phonon line at 1.039 eV was identified as an intracenter transition within AsGa. An excellent correlation was found between the intensity of the no-phot1n AsGa line and the characteristic EL2 absorption. A correlation was also found between the characteristic optical absorption of EL2 and its concentration as determined by DLTS measurements. These results prove the direct association of EL2 with a neutral state of AsGa The presence of another midgap level ELO, contained in heavily doped oxygen crystals had no effect on the optical spectra of EL2, but it did alter the DLTS measurements. Thus, an accurate calibration was obtained for the determination of EL2 by optical absorption based on DLTS measurements on crystals containing only EL2 and thus involving no uncertainties introduced by other midgap levels.
Spatial Distribution of Neutral EL2 as Measured Optically for Thin Semi-Insulating GaAs Wafers, and Relevance to Device Parameters
Authors: Dobrilla P. , Blakemore J. S. , Gleason K. R. , McCamant A. J.
Published: March 2011

Measurements are reported, for 0.5 mm thick semi-insulating (S.I.) GaAs wafers, of the neutral EL2 distribution, the pattern of dislocations, and of MESFET electrical parameters - these devices built on the same wafers. These results indicate that the device properties are more affected by EL2 nonuniformity than by dislocation density pattern.
Defect Identification in Silicon Using Electron Nuclear Double Resonance
Authors: Ammerlaan C.A.J. , Sprenger M. , Kemp R. Van , Wezep D.A. Van
Published: March 2011

The application of electron nuclear double resonance (ENDOR) for identification and characterization of point defects in silicon is reviewed. Taking the vacancy and the boron-vacancy complex as examples it is discussed how ENDOR can provide information on the atomic and electronic structure of paramagnetic centers.
Endor-Investigation OF Al ++ AND Al ++-Al- PAIRS IN SILICON
Authors: Niklas J.R. , Spaeth J.-M. , Watkins G.D.
Published: March 2011

With Electron Nuclear Double Resonance (ENDOR) ligand superhyperfine (shf) interactions were investigated for 7 neighbor shells of the interstitial Al ++ center (Si-G18) and for 10 neighbor shells of the Al ++-Al-pair center (Si-G19). All shells of the interstitial center exhibit undistorted Td symmetry confirming the defect model derived from earlier experiments. In the pair center the shf interaction of the Al++ with the neighboring Al nucleus shows a pure [111]-symmetry, also the shf interactions with the outer Si-neighbor shells exactly reflect this axial [111]-symmetry of the defect. The magnitude of the quadrupole interaction of the neighboring Al nucleus clearly shows, that this nucleus is a nearest neighbor of the Al++. From the angular dependence and the intensity ratios of ENDOR lines of the pair center it can be excluded that any additional impurity is associated with the Al++-Al- pair at least within the first 3 neighbor shells of the AI++. The influence of the Al- neighbor on the hyperfine axes of the first [111] Si-neighbors is negligible and is also remarkably small for the other Si-neighbors. The magnitudes of the ligand shf interactions for the pair center are closely related to those of the Al++ center. A comparison of these values for both centers allows a definite assignment of the measured shf interactions to their corresponding neighbor shells for the Al++ center.
The Effect Of Uniaxial Stress on the Infrared Absorption Bands Due to the Oxygen Donor in Silicon
Authors: Stavola M. , Lee K. M. , Nabity J. C. , Freeland P. E. , Kimerling L. C.
Published: March 2011

We have investigated the effect of stress upon the infrared absorption spectrum of the neutral charge state of the oxygen donor in silicon. Our results show that the central cell of the donor has C2ν, symmetry and that this anisotropy gives rise to a ground state wave function that is constructed from a single pair of conduction band valleys.
Thermal Donor Removal by Rapid Thermal Annealing: Infrared Absorption
Authors: Stein Herman J. , Hahn S. K. , Shatas S. C.
Published: March 2011

Rapid thermal annealing of thermal donors in Si with 10 sec anneal times at temperatures between 600 and 1000 °C has been investigated by infrared absorption at 80 K. Thermal donors A through D, which are identified by excited state absorption, are present in as-grown Czochralski Si; whereas excited states for donors A through F as well as photoionization of thermal donors are observed after extended heating at 450 °C. The temperature required for rapid thermal annealing is lower when only donors A through D are present. Removal of thermal donors A through F by rapid thermal annealing at temperatures > 800°C restores 7 to 8 oxygen atoms to interstitial sites per electricallӯ measured donor removed. This ratio supports oxygen cluster models for thermal donors but does not support previous suggestions that such clusters are embryonic forms of high temperature oxygen precipitates.
Identification of Impurities and Defects in Semiconductors by Optical Spectroscopy
Authors: Skolnick M. S.
Published: March 2011

A review is given of the information that can be obtained on defect centers in semiconductors by optical spectroscopy. Particular emphasis is given to donor and acceptor identification, and symmetry determination of transition metal and axial defect-complex centers. The information that can be obtained from isotope doping effects is discussed.
Infrared Mapping of Oxygen and Correlation with Electrical Measurements on CZ Grown Wafers
Authors: Whitfield J. , Boyle R.
Published: March 2011

Spatial variation of interstitial oxygen concentrations ([Oi]) have been observed in wafers sliced from CZ grown ingots. Oxygen precipitation can occur with subsequent heat treatments causing non-uniform electrical device characteristics across a processed wafer. A new method is presented using infrared absorption measurements to map [Oi]in silicon wafers for correlation with wafer electrical measurements. The new infrared mapping method uses a spectrometer fitted with a software controllable wafer positioner. 100 m m diameter wafers were mapped to show the concentration variations and oxygen precipitation effects resulting from thermal heat treatments. Electrical measurements were made on nearly adjacent wafers from the same ingot and subjected to the same thermal cycling plus a diode-capacitor fabrication process. Two types of electrical measurements were used to map diode-capacitor arrays: reverse leakage current (Ir) and transient reverse recovery lifetime (τr. The measured values for each device tested were positionally correlated to the fourier transform infrared spectrometer (FT-IR) [Oi] data. Scatter plots were generated by plotting the electrical measurements as a function of the interpolated concentration data or differential concentration data parameterized at equivalent positions on the wafers. The scatter plots show that the electrical characteristics are strongly dependent on the precipitated oxygen (∆ [Oi]) for larger values of ∆[Oi], but nearly independent for lower ∆[Oi] values.
Oxygen-Nitrogen Interactions in Ion-Implanted Silicon
Authors: Stein H. J.
Published: March 2011

Interaction of oxygen and nitrogen in ion-implanted crystalline silicon layers has been investigated by infrared absorption. Infrared absorption bands which are not produced by either 14N or 160 alone are observed after sequential implantation of 14N and 160 into overlapping profiles followed by annealing at 500°C. The new bands indicate oxygen - nitrogen interactions and are ascribed to Si-N vibrational modes with oxygen in nearby interstitial sites.
Defect States in GaAs after Rapid Thermal Annealing
Authors: Street R. A. , Johnson N. M. , Burnham R. D.
Published: March 2011

Electronic deep levels in GaAs have been investigated by correlated luminescence and DLTS measurements on material in which the defects were systematically perturbed by rapid thermal annealing. The samples were grown by MOCVD and encapsulated with silicon nitride. Annealing was performed at temperatures from 800°C to 950°C for 5 seconds. The luminescence spectra were measured from 0.7 to 1.6 eV at temperatures from 4-80 K and have features at 0.97, 1.17, 1.35, 1.40 and 1.5 eV. The band-to-acceptor luminescence shows the formation of Si acceptors, starting at an anneal temperature of about 850°C. The luminescence peak at 1,35 eV, attributed to As vacancy - acceptor complexes, is observed to increase in intensity with higher annealing temperatures. In contrast, the Ga vacancy-donor complex peak at 1,17 eV decreases in intensity. DLTS data show an increase in the density of deep levels and new levels not present in the unannealed material. Capacitance-voltage data find a reduction in carrier concentration, although type conversion is not observed even after annealing to 950°C.
The Donor State of Vanadium in Indium Phosphide
Authors: Bremond Georges , Nouailhat A. , Guillot G. , Deveaud B. , Lambert B. , Toudic Y. , Clerjaud B. , Naud C.
Published: March 2011

We have performed studies on Vanadium doped InP, especially p-type InP codoped with Zn and V. Luminescence excitation experiments, DLTS, DLOS and absorption experiments lead to the conclusion that the donor level (V3+/V4+) of Vanadium is at about 0.2 eV above the valence band. Optical cross-sections that are determined by DLOS allow to observe for the first time a resonance in the valence band of a III-V semiconductor that we tentatively interpret as an excited state of V4+.
Defects in GaAs as Revealed by Chemical Etching
Authors: Lessoff H. , Tseng W.
Published: March 2011

A new eutectic etchant for GaAs has been developed to display (a) the normal etch pit patterns, but also to reveal (b) rectangular, (c) shallow matrix and (d) raised geometric patterns. Results on various GaAs substrates, ranged from undoped to In-, Cr-, Te-, Si-doped materials, show a general trend: The materials having the numbers of (a), (b) and (c) etched patterns are roughly in the above order (from high density to low density). Whereas, for the density of the raised geometric patterns, the ranking is reversed. It is concluded that the major factor in developing the (a), (b) and (c) etched patterns is due to the stress, while the (d) pattern may be due to dopant and its influence on Ga to As bondings.
Charge Trapping by Deep Donors in Si-Doped AlxGa1-xAS
Authors: Mooney P. M. , Caswell N. S. , Solomon P. M. , Wright S. L.
Published: March 2011

The kinetics of charge capture by deep donors in AlxGa1-xAs have been measured. The time dependence indicates that a single energy cannot be used to describe the trap. A model assuming thermally activated capture into a resonance in the conduction band with a range of energies gives excellent fits to the data and provides a measure of the energy range for the trap. This model is consistent with the large lattice relaxation model for DX centers. The increase of the activation energy for capture as the Al mole fraction is decreased contradicts the model which attributes the decay of the persistent photoconductivity to tunneling through the heterojunction barrier in modulationdoped structures.
The Effect of Hydrostatic Pressure on Defect Annealing in Semiconductors
Authors: Barnes C.E. , Samara G.A.
Published: March 2011

We report the first study of the effect of hydrostatic pressure on the annealing of defects in Si and GaAs. It is shown that the application of hydrostatic pressure enhances the annealing rate in these materials. Analysis of the data yields the lattice volume relaxation accompanying annealing.
Acceptor and Donor Impurities in Semiconductors Studied by the PAC—Method
Authors: Forkel Doris , Futtinger H. , Iwatschenko-Borho M. , Meyer F. , Witthuhn W. , Wolf H.
Published: March 2011

The perturbed angular correlation method (PAC) is applied to semiconductors. This technique is based on the detection of the electric quadrupole hyperfine interaction by means of radioactive nuclei. The highly localized sensitivity of the PAC-method favours the investigation of localized distortions of the lattice due to impurities as donor or acceptor atoms.

Results are given for radioactive 111Cd atoms in the semiconductors In2 Te5, ZnO, and Si. The observed electric field gradients (EFG) and their orientations with respect to the crystal axes yield information on the local structure around the probe atoms. In Na—or Li—doped ZnO the formed Na—O—In (or Li—O—In) complexes show identical axial symmetric EFG tensors. In the case of In2Te5 acceptor level energies could be deduced from the temperature dependence of the EFG.
Dislocation Trapping Potential Measured by SEM-CCM
Authors: Mil'Shtein Sam
Published: March 2011

The intensity of contrast and width of the image of a single dislocation in silicon were measured versus bias of Schottky barrier at room temperature. A regime of measurements was established, which reduced dramatically the number of variable parameters involved in contrast formation. In addition, using the right regime of SEM-CCM one can determine the position of a defect relative to the surface of the specimen without doing TEM measurements. It was shown for the first time that from contrast readout one can determine the dislocation electrical potential. A model of image formation is discussed.
Electronic Ground State of Iron-Acceptor Pairs in Silicon
Authors: Ammerlaan C.A.J. , Kooten J.J. Van
Published: March 2011

Iron-acceptor impurity pairs, consisting of a positively charged iron ion trapped on an interstitial site in the vicinity of an ionized acceptor, in silicon were observed by electron paramagnetic resonance for all common acceptor dopants (B, Al, Ga, In). The Zeeman splittings of these pairs, to which both spin and orbital momenta contribute, cover the range between 1.1 and 6.4. An interpretation of these spectroscopic splitting factors is presented, which considers the effects of the crystal field - of cubic, axial, or lower symmetry - and of spin-orbit interaction on the 4F ground state of the iron ion in a (3d)7 configuration. It is concluded that the apparent quenching of the orbital angular momentum is not due to a dynamical Jahn-Teller effect, nor due to hybridization. Rather, it is proposed that a significant reduction, by about 80%, of the orbital magnetism arises from covalency.
Ebic Analysis of Hydrogen Passivation of Defects in Silicon
Authors: Hanoka J.I. , Dube C.E. , Sandstrom D.B.
Published: March 2011

EBIC evidence of the key role of dislocations in hydrogen passivation of EFG ribbon is presented. Dislocations, and not bulk point defects, are shown to be both the principal defect being passivated and the means whereby rapid thermal diffusion of hydrogen takes place. Passivation of dislocation arrays to depths of the order of hundreds of microns has been observed. Low stemperature EBIC (96°K < T < 300°K) has shown that shallow electron traps associated with dislocations and within ∼0.1 eV of the conduction band are not passivated while (proposed) deeper mid-gap levels at the same spatial location are readily passivated. A general dislocation model for hydrogen passivation applicable to all polycrystalline silicon is presented.
Direct Measurement of the Subsurface Hydrogen Barrier Layer in Plasma-Treated Silicon Ribbon
Authors: Jaworowski A.E. , Wielunski L.S. , Listerman T.W.
Published: March 2011

The near-surface hydrogen profile was measured using the 15N hydrogen profiling technique in silicon ribbon grown by the edge-defined film-fed growth (EFG) process. This direct method has a high depth resolution of 10 - 30 Å, can be used to a depth of several microns, and can measure hydrogen in concentration of 100 at. ppm. By appropriate surface treatment we were able to observe for the first time the separation of the near-surface hydrogen profile in silicon from the surface hydrogen contamination layer. Using our technique, hydrogen profiling of the near-surface region revealed the existence of a subsurface hydrogen layer which acts as a barrier to the transfer of hydrogen into the bulk of both passivated and untreated silicon. The structure of this hydrogen barrier was measured for different plasma treatments.
Exponential Band Tails at Silicon Grain Boundaries
Authors: Werner J. , Peisl M.
Published: March 2011

The energy-distribution of interface states at grain boundaries in fine-grained silicon films is measured by two independent methods. The analysis reveals deep exponential band tails in the two-dimensional density of states within the band gap. It is proposed that these tails originate from Anderson localization of free carriers within potential fluctuations along the grain boundary plane. The measurements are in good agreement with this model.
Photoluminescence and Raman Spectroscopy of Cubic SiC Grown by Chemical Vapor Deposition on Si Substrates
Authors: Freitas J.A. , Bishop S.G. , Addamiano A. , Klein P.H. , Kin H.J. , Davis R.
Published: March 2011

Thin films of cubic SiC were grown on Si substrates by a new CVD heteroepitaxial technique. The cubic polytype and crystal quality were verified by room temperature Raman spectroscopy. Low temperature photoluminescence (PL) studies detected nitrogen donor bound excitons, N-Al donor-acceptor pairs in Al-doped samples, and some defect complexes usually observed only in irradiated samples. Evidence of strain due to the Si-SiC lattice mismatch was observed in both the Raman and PL spectra and the effects of substrate removal and high temperature annealing on these optical spectra were studied.
In Situ Measurement of Stress. Included During Annealing, in A1-2%Cu Thin Films
Authors: Townsend P. H. , Plas H. A. Vander
Published: March 2011

Stress measurement in thin film systems is discussed and applied to Al-2%Cu filns on SiO2/Si substrates during thermal cycling. Plastic deformation obscrved during compressive stress relaxation is correlated with the formation of hillocks on the metal films. The effect of secondary layers of 10%Ti-90%W on the thermo-mcchanical response of Al films is examined.
Metal-Germanium Contacts and Germanide Formation
Authors: Marshall E. D. , Wu C. S. , Pai C. S. , Scott D. M. , Lau S. S.
Published: March 2011

In this study, we survey germanide formation and characterize Schottky- barrier properties for a number of representative metals on Ge (Al, Ag, Au, Er, Ni, Pd, Pt, Ta and Ti). It is found that the germanide formation characteristics (sequence of phase formation, kinetics, moving species) are similar to those of the corresponding silicides. The Schottky-barrier heights, however, are all similar and centered around 0.59 eV arida re relatively insensitive to the metallization.
Esca Studies of the Valence band and Loss Spectra of Semiconductor Films: Ionicity and Chemical Bonding
Authors: Barr T. L. , Kramer B. , Shah S. I. , Ray M. , Greene E.
Published: March 2011

ESCA valence band and core level loss results have been determined that appear to be directly related to the degree of covalency/ionicity and other bonding features of certain semi-conductor systems. Specific applications are presented that aid in the characterization of the key chemistry of dielectric oxide/semiconductor interfaces and also may help to determine the relative metastability of the solid solution of Group IV elements (e.g., Ge) into certain III-V lattices (e.g., GaAs). It is shown that these features are not detectable through conventional core level shift arguments, and that the aforementioned novel approaches often require high resolution ESCA.
The Production of Doped Amorphous GaAs by Co-Sputtering With Mo
Authors: Najar S. , Sedeek K. , Lalande F. , Carchano H.
Published: March 2011

Stoichiometric amorphous GaAs films with intrinsic properties have beer produced by R.F. Sputtering in pure argon at high substrate temperature of 290°C. The electronic and the optical properties of this material have been modified by the molybdenium co-sputtering. This paper reports: on several modified material parameters including the electrical conductivity, thermal activation energy and optical gap. Atomic Mo concentrations up to 1.24% have been investigated. It is observed that the room temperature conductivity can be controlled over about six orders of magnitude, which corresponds to a shift in the Fermi level of 0.45 eV towards the conduction band edge. For optical parameters, the optical gap has been reduced by 0.1 eV. An additional absorption tail due to localized states introduced by doping atoms is observed. It is concluded that our a-GaAs have the main requirement, i. e low density of defect gap states, for effective doping with analogy to a-Si prepared either by glow discharge or by sputtering in argon-hydrogen plasma.
Adhesion at Metal-Ceramic Interfaces: Ion Beam Enhancement and the Role of Contaminants
Authors: Baglin J. E. E.
Published: March 2011

Enhanced adhesion of a film of non-reactive metal deposited on a ceramic or glass substrate can be produced by irradiating the interface with an ion beam. The resulting bond can be improved by subsequent heat treatment. The interface remains abrupt. The mechanism of this bonding is discussed, and the effects of interface contaminants are examined for the Cu-Al2O3 and Au-Al2O3 systems. Finally it is noted that strong adhesion is produced when Al2O3 is subjected to preferential sputtering at the time of Cu deposition; the resulting interface chemistry is discussed.
Optical Behavior of Sputter-Deposited Aluminum Nitride: Relationship to Film Cheiistry
Authors: Kubiak C. J. G. , Aita C. R. , Hickernell F. S. , Joseph S. J.
Published: March 2011

Films which are nominally aluminum nitride were grown by reactive sputter deposition using an aluminum target and rf-excited nitrogen discharges operated at power levels from 100 to 800W. Depositions were made on water-cooled (111)-cut Si and amorphous quartz substrates. The optical behavior of these films and its relationship to chemistry is discussed in the present paper.
Photo-Induced Excess Conductivity in Doping Modulated Amorphous Semiconductors
Authors: Kakalios J. , Fritzsche H.
Published: March 2011

The metastable excess conductivity σ(E) observed in hydrogenated amorphous silicon (a-Si:H), that is alternately doped n- and p- type, is compared with the Staebler-Wronski effect and other metastable conductivity changes observed in compensated a-Si:H and in oxidized p- type a-Si:H respectively. We find that Dohler's model of electron-hole pair separation in the pn-junction fields cannot account for the long life of a(E) near and above 300ºK. A defect complex associated with boron having a large configurational relaxation after releasing an electron by photoexcitation is considered as an explanation for σ(E).
An Assessment of a-SiGe:H Alloys with a Band GaP of 1.5Ev as to their Suitability for Solar Cell Applications
Authors: Roedern B. Von , Mahan A.H. , McMahon T.J. , Madan A.
Published: March 2011

Hydrogenated amorphous silicon germanium alloys a-Si1-xGex:H are being actively investigated for their application as a low band gap material in cascade solar cells [1,2]. To date, such alloys produce material of reasonable electronic quality only if the Ge-content is kept low (<40 at.%) such that the band gap is not decreased much below 1.5 eV. Conversion efficiencies of -5% have been obtainedwith alloys having such a band gap, and tandem cells have shown conversion efficiencieswhich are lower than those of good quality single layer a-Si:H devices. Thus, the performance of alloys is well below that necessary to achieve conversion efficiencies of >16%, which are ultimately hoped to be obtained using the cascade approach [2]. Other low band gap alloys such as a-Si1-xSnx:H have been shown to be even less suitable with regard to their electronic properties [3]. The cause of the degradation in electronic properties with increased alloying is not yet understood. Factors such as preferential attachment of H to Si rather than Ge [4] or microstructure observed in alloys have been suggested as a cause for the electronic degradation, [5,6] but no unique correlations have been established between such findings and the electronic properties.
Bonding and Release of Hydrogen in a-Si:C:H Alloys
Authors: Beyer W. , Wagner H. , Mell H.
Published: March 2011

Hydrogen evolution and infrared absorption studies of a-Si:C:H films prepared from mixtures of hydrocarbon (CH4' C2H6' C2H4) and silane gases (SiH4 'Si2H6)by the glow-discharge process show that both the absolute hydrogen content and the hydrogen bonding is uniquely determined by the carbon content. Up to a carbon concentration of ∼45 % the widening of the optical gap is mainly due to an increase of the hydrogen content. For a hydrogen density NH > 1- 2x1022cm-3 the incorporated hydrogen atoms lead to the formation of voids, resulting in thermal instability of the bonded hydrogen and in a deterioration of the electronic quality of the amorphous material.