bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties of a-Si:H and a-SiGe:H Films Deposited by Photo-Assisted CVD
Authors: Rocheleau R. E. , Jackson. S. C. , Hegedus S. S. , Baron B. N.
Published: March 2011

Chemical vapor deposition techniques, in particular plasma enhanced CVD, have been used to produce high quality a-Si:H materials. Continuing research is directed toward increased device performance, improved stability, and translation of scale to commercial production. A part of this effort is the evaluation of alternate CVD techniques which in addition to providing technical options for high efficiency and long term stability are likely to lead to improved understanding of the relationships between deposition processes and material properties. A relatively new technique for depositing a-Si:H is photo-CVD which utilizes ultraviolet light to initiate the decomposition of silane or disilane. The best results from both materials properties and device efficiency points of view have been achieved using mercury sensitized photo-CVD. Recently, a 10.5% efficient a-Si:H p-i-n photovoltaic cell, fabricated by photo-CVD, was reported [1]. A limitation in photo-CVD has been preventing deposition on the UV transparent window. In this paper we describe a new photo-CVD reactor with a moveable UV-transparent Teflon film and secondary gas flows to eliminate window fouling. The deposition and opto-electronic characterization of intrinsic a-Si:H and a-SiGe:H and p-type a-SiC:H are described. Finally, preliminary results of p-i-n solar cells are presented.
Ohmic and Quasi-Ohmic Contacts to Hydrogenated Amorphous Silicon Thin Films
Authors: Kanicki Jerzy , Bullock Dan
Published: March 2011

An extensive study of contacts properties to undoped and doped hydrogenated amorphous silicon, undertaken in our laboratory, has shown that ohmicity and contact quality are very dependent on the reactivity of the metal and the quality of the metal / a-Si:H interface. For example, metals such as Sc, Mg or Ti form exceptionally good ohmic (very low barrier height) contacts, while others like Al, Cu, Mo or V form very poor quasi-ohmic contacts (average barrier height) to undoped films. In addition, metals such as Y, Ho, Hf or Er create fair quasi-ohmic (low barrier height) contacts to undoped films, at room temperature. The barrier height and the magnitude of current density can be adjusted to some degree not only by the proper choice of metal work function but also by changing material bulk resistivity or/and interface quality. Consequently, specific attention is devoted to these parameters which not only determine the quality of ohmic contact but also the dominant conduction mechanism across the barrier.
UHV Interface Studies of Palladium Silicide Formation on Hydrogenated Amorphous Silicon Films
Authors: Rhodes H. E. , Apai G. , Rivaud L. , Hung L. S. , Mayer J. W.
Published: March 2011

Silicide formation by reaction of palladium metal (Pd0) with hydrogenated amorphous silicon (a-Si:H) substrates was studied with Rutherford backscattering spectrometry (RBS), forward recoil spectrometry, x-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). Upon low-temperature (200° C) annealing, RBS and TEM show a single-phase Pd2Si. This phase grows with the square root of time, and the activation energy is identical to that of the corresponding metal on single-crystal silicon substrates. The growth is slightly faster for hydrogenated amorphous silicon, which is attributed to its amorphous structure. During silicide formation, the hydrogen is released from silicides and presumably outdiffuses into a vacuum without interfacial accumulation. Thus, barrier formation does not occur, and the presence of hydrogen in the substrates has no effect on silicide growth.

The silicide electronic structure (core level binding energies, lineshapes, and d-band filling) of Pd2 Si on a-Si:H is identical to that of Pd2 Si formed on cr stalline silicon. Binding energy and peak shape analysis show the Pd2Si/Pd0 interface to be composed of one additional phase, Pd4Si, which has a well-defined binding energy (335.8 eV) and a narrow (FWHM = 1.1 eV), symmetric line shape. It has long been postulated that interface phases may be important in determining the phase sequence in silicide growth and the dominant diffusing species. This Pd4 Si interface phase may be important in understanding palladium silicide growth.
Transport Properties of Amorphous Silicon / Silicon Oxide Heterostructures
Authors: Steemers H. , Mort J. , Chen I. , Jansen F. , Grammatica S. , Kuhman D.
Published: March 2011

The transport of excess carriers in glow-discharge deposited a-Si:H/insulator heterostructures has been studied by time-of-flight and xerographic discharge techniques. Efficient injection of photocarriers from a-Si:H into, and transport through, relatively thick SiOx:N:H has been achieved. A mobility-lifetime product approaching 18−6 cm2V−1 is found for electrons in SiOx:N:H, and time resolved measurements indicate a room temperature mobility of 5×10−6 cm2v−1s−1 at a field of 2×104 Vcm−1, suggesting an electron lifetime of the order of 8.2 seconds. The results are contrasted with transport measurements on thermally grown SiO2 on Si and a transport model involving hopping through defect states within the gap of SiOx:N:H is discussed.
Optoelectronic Properities of A-Ge:H/A-Si:H Superlattic Structures
Authors: Wronski C. R. , Persans P. D. , Abeles B. , Tiedje T. , Hicks M.
Published: March 2011

The optoelectronic properties of multilayer a-Ge:H/a-Si:H superlattices with bandgaps between ˜1.4 and 1.1eV are presented. The dependence of the electronic properties on the band alignment and the layer thicknesses is established and quantified. Particular emphasis is given to properties relevant to practical device applications and which involve carrier transport perpendicular to the layers.
Impurities and Metastable Centers in Amorphous Silicon Solar Cells
Authors: Carlson D. E.
Published: March 2011

Amorphous silicon solar cells are adversely affected by impurities through the creation of traps, recombination centers and metastable centers. The microstructure of discharged-produced, hydrogenated amorphous silicon (a-Si:H) appears to be strongly affected by the presence of impurities in the discharge atmosphere. A model is developed in which impurities create microvoids in a-Si:H, and traps, recombination centers and metastable centers are associated with the internal surfaces of the microvoids. In this model, hydrogen plays an important role in determining the electronic activity and diffusivity of impurities, and metastable centers are created by the trapping of holes near microvoids and the induced motion of hydrogen on the internal surfaces of the microvoids.
Fabrication of the Large-Area Integrated a-Si Solar Cells
Authors: Yamazaki S. , Abe M. , Nagayama S. , Shibata K. , Susukida M. , Fukada T. , Kinka M. , Kobayashi I. , Inushima T. , Suzuki K.
Published: March 2011

PIN-structure small-area solar cells using a-Si have been frequently reported on, but only a few reports are available on the study of solar cells using a large-area (10-cm square) substrate, all with a resultant conversion efficiency of above 9.0 %[1,2]. Our study has been concentrated on solar cells using a batch of ten 10-cm square substrates with an average conversion efficiency of 9.5 % or more.

As a result, without an anti-reflection coating on the surface of the glass substrate, the following values have been obtained: average conversion efficiency (EFF)=9.63 % (standard deviation of 0.195 %) -Open-circuit voltage (Voc)=12.668 V (standard deviation of 0.215 V) -Short-circuit current (Isc)=78.467 mA (standard deviation of 1.619 mA) -Fill factor (FF)=0.6672 (standard deviation of 0.009)

The process, equipment and methods for measurements through which these results were obtained are described below.
Properties of Amorphous Silicon Films Deposited at Rates Higher Than 1 μM/MIN.
Authors: Chu T. L. , Chu Shirley S. , Ang S. T. , Duong A. , Han Y. X.
Published: March 2011

The thermal decomposition of disilane in a helium flow has been used for the deposition of hydrogenated amorphous sil icon (a-Si:H) films on various substrates at rates higher than 1 μm/min, and a-SI:H films with thickness up to 20 μm have been deposited in this manner. Their optical properties, photoconductivity, minority carrier diffusion length, gap state density, etc., have been measured. The electronic properties of these films are superior to those of chemical vapor deposited a-Si:H films heretofore reported, indicating that the thermal decomposition of disilane in a hel ium atmosphere is a promising technique for the deposition of a-SI:H films.
Integrated Series Connection of a-Si:H Solar Cells
Authors: Juergens W. , Kausche H. , Peters W. , Stetter W.
Published: March 2011

We tested several methods of patterning amorphous-silicon (a-Si:H) solar cells to form stripe cells and to connect these stripe cells integrated with cell deposition process to a series-connected module. The patterning techniques used included: laser cut, screen print lift-off techniques, adhesive tapes with lift-off, and a special mechanical milling method. The three layers of a cell which must be patterned are 1. SnO2 :F on glass, 2. a-Si (p(C)in), 3. metal-electrode.

We developed a convenient patterning method for a laboratory size with a loss of area of 13 %: 1. laser cut, 2. milling, 3. adhesive tape lift-off. For a higher level of production we tested the following sequence with a loss of area of 4 %: 1. screenprint and lift-off, 2. milling/slotting, 3. screen print and lift-off. The last method has the advantage that without any laser treatment the costs are only third of those of the other methods with a laser cut; so we will eliminate the laser cut in future for manufacturing modules.
Temperature and Light Intensity Dependences of Open Circuit Voltage in a-Si: H Pin Solar Cells
Authors: Jang Jin , Lee Choochon
Published: March 2011

The temperature and incident light intensity dependences of open circuit voltage for hetero-and homojunction a-Si:H pin solar cells have been studied. The temperature coefficient of the open circuit voltage decreases from -2.40 to -2.67 mV/°C as the illumination intensity is decreased from 150 to 7mW/cm2 This is consistent with the empirically calculated open circuit voltages. The diode quality factor obtained under dark condition shows high values(l.6–3.0) and strong temperature dependence. On the other hand, the diode quality factor under illumination is less than 1.5 and shows slight temperature dependence. The results appear to be due to the long dielectric relaxation time compared with the carrier lifetime in the i-layer.
Experimental and Theoretical Results for Light Trapping in High Efficiency a-Si1-xCx:H/a-Si:H Solar Cells Prepared on Granular Tin Oxide.
Authors: Ellis F. B. , Delahoy A. E. , Böhm M. , Cambridge J. A. , Horning T.
Published: March 2011

We examine the morphology and optical properties of fluorine doped tin oxide films prepared by the chemical vapor deposition of tetramethyltin and tin tetrachloride and the influence of these properties on light trapping in amorphous silicon solar cells having the structure glass/SnO2 /P (a-Si1-xCx:H) -i-n/metal. Measured tin oxide properties include total and diffuse transmission as a function of wavelength, angular dependence of the scattered light, surface topography, and sheet resistance. Experimental quantum efficiency plots as a function of wavelength are presented and compared to computer calculations based on multilayer optics programs and measured optical constants. Using granular tin oxide, p-i-n cells 1 cm2 in area have been prepared with efficiencies exceeding 10%.
Properties of Indium Tin Oxide Films Prepared Using Reactive RF Magnetron Sputtering
Authors: Mehra Madhav , Rhodes Howard
Published: March 2011

The results obtained upon reactively RF sputtering indium - tin oxide (ITO) films are presented. It is found that while the amount of oxygen in the chamber is very critical in determining the properties of the films, it is easy to deposit reproducible films even at low oxygen concentrations when using an oxide target. At concentrations of oxygen below 2 vol% the films deposited exhibit almost metallic conductivities, while retaining an average transparency in the visible range of over 85%. The resistivity of these films increases with the oxygen concentration in the chamber, but the transition is not as sharp as that observed upon sputtering a metal target. These films are found to have very good “figures of merit” and are promising in their use as transparent conductors.
A Comparative Study of Hydrogenated Amorphous Silicon Films Prepared by RF Sputtering in He/H2, Ar/H2 and Xe/H2 Mixtures
Authors: Albers Mark L. , Shanks H. R. , Shinar J.
Published: March 2011

Preliminary results of a comparative study of some optical and ESR properties of aSi:H films prepared by rf sputtering on a cold substrate in 10 mtorr of either He, Ar, or Xe and 0.5 mtorr H2 are presented. In all cases the concentration of Si-H and Si-H2 bonds, the optical gap and the dangling bond spin density all generally increase as the rf power is decreased from 3.3 to 0.27 W/cm2. However, whereas the optical energy gap of He/H2 sputtered films ranges from 1.26 eV to 2.13 eV, the gap of Ar/H2 and Xe/H2 films sputtered under these conditions only changes from 1.54 to 1.94 and 1.41 to 1.71 eV, respectively. The dangling bond spin densities are lowest (~1017 cm-3) in the Ar/H2 sputtered films at high rf power and highest (~5x1018 cm-3) in Xe/H2 sputtered films at low power.
Proplriies of Post-Hydrogenated Amorphous and Microcrystalline Germanium Films
Authors: Woodyard James R. , Gonzalez-Hernandez J. , Young R. T. , Piontkowski J.
Published: March 2011

Amorphous and microcrystalline germanium films prepared by glowdischarge and molecular beam deposition were hydrogenated after deposition, using a 3cm Kaufman ion source. The hydrogen profiles were determined using the N15p nuclear resonance reaction. We found that the surface region hydrogen concentration depended on ion beam modification of the material, and the bulk concentration was determined by the hydrogenation conditions and deposition conditions. The light and dark conductivities wee measured before and after hydrogenation. Several orders of magnitude change in the ratios of the conductivities were measured under optimum hydrogenation conditions. The aclivation energy for electrical conductivity was measured and found to be dependent on film structure thickness and hydrogenation conditions.
Novel a-Si:H Thin Film High Voltage Transistor
Authors: Tuan Hsing C.
Published: March 2011

A new novel thin film high voltage transistor in a-Si:H is described in this paper. This new structure extends the operation of a-Si:H TFT to 500 volts or more. The fabrication process of this new high voltage transistor is simple and compatible with that of the conventional low voltage TFT. The high voltage TFT can be switched by low voltage signals and is demonstrated to be capable of switching several hundreds of volts.
Crystallization Rate and Thermal Stability of Te-Based Alloy Thin Films for Erasable Optical Recording
Authors: Ross R. C. , Strand D. A. , Bjornard E. J. , Deneufville J. P.
Published: March 2011

Erasure speed and thermal stability of a number of Te-based alloys have been measured and compared. A distinct trend of increasing crystallization temperature, Tx, and increasing minimum time required for crystallization, τx, with increasing crosslinking element content is observed. Films which crystallize to form Te are stability limited at Tx≈80°C for τx≈┐μsec. Films which crystallize to form Sb40Te45Se15have Tx160°C at τx≈┐μsec. Static tester recrystallization kinetics and direct observation of cycled tracks by optical and electron microscopy indicate that recrystallization occurs via epitaxial growth from peripheral crystallities and not from internally dispersed nuclei for all materials studied. Thus, crystallization speed is limited by three factors: the intrinsic maximum crystallization velocity of the pure crystal, the diffusion rate of crystal-insoluble crosslinking elements away from the crystallization front, and the geometry of the amorphous and peripheral crystalline zones
Planar and Perpendicular Conductivity of Doping Modulated Amorphous Silicon Multilayers
Authors: Steemers H. , Chen I. , Mort J. , Jansen F. , Morgan M. , Kachonkin N. , Kuhman D.
Published: March 2011

The conductivity of a-Si:H multilayers consisting of alternating boron and phosphorus doped layers has been studied as a function of sub-layer thickness. The planar and perpendicular dark conductivity is compared with theoretical analysis of space-charge doping in these structures and this effect is found to dominate the transport as the sub-layer thickness is reduced below a critical value
Bond Angle Disorder in Tetrahedrally Bonded Amorphous Silicon
Authors: Wong C. K. , Lucovsky G.
Published: March 2011

There have been many studies of the vibrational and optical properties of a- Si and a-Ge that have correlated systematic variations of these properties with films grown and/or annealing temperatures, and have attributed these variations to changes the local atomic structure and intrinsic network disorder that are correlated with the thermal history of a particular sample. The most frequently proposed atomic structure parameter associated with this intrinsic disorder has been the width of the bond angle distribution. We attempted to isolate the effects of bond angle disorder on the vibrational and electronic properties of a-Si using a Bethe Lattice structure that avoids some of the uncertainties introduced by the uncontrolled variation in other atom structure parameters. Using this approach, we show that increases in the width of the bond angle distribution can account for trends in the calculated vibrational and optical properties wth thermal hisrory that are in good qualitative agreement with trends reported in the experiments.
Ab-Initio Theory of Defect Structure in a-Si iH
Authors: Bar-Yam Yaneer , Joannopoulos J. D.
Published: March 2011

It has recently become feasible that theory Will be able to predict the structure of solids “ab-initio”, using only the atomic number of the constituent atoms as input. This is based on recent advances in density-functional theory and pseudopotential theory. A simple physical introduction of the concepts underlying these theories is presented. Special emphasis is given to examining the structure and effective correlation energies of defects in amorphous Si.
Defect Structures Generated by Buried Amorphous Layer Regrowth in <100> Arsenic Implanted Silicon
Authors: Jones Kevin S. , Prussin S.
Published: March 2011

Plan-view and 90° cross-sectional TEM examination was used to investigate the correlation between the type of amorphous layer produced and the resulting defect structure observed upon annealing. Both <100> and <111> Si wafers were ion implanted with high energy (190 keV) arsenic over a range of doses(1 × 1015/cm2 to 5 × 1015/cm2). A Wayflow endstation was used allowing ion beam induced epitaxial crystallization (IBIEC)[8] or dynamic annealing of the sample to occur. Implanted <111> Si is shown to form a continuous amorphous layer up to the surface, while <100> implanted Si forms a buried amorphous layer. The regrowth of the buried x-layer by furnace annealing is shown to be responsible for the formation of shear type dislocation loops at the interface where the two x/c regrowth fronts meet (catagory IV defects).[7] However if the buried layer is regrown by dynamic annealing a different structure results.

In addition to using <111> wafers, other parameter changes which resulted in the formation of surface amorphous layers included decreasing the implant energy from 190 keV to 100 keV, or implanting the wafer at 77K instead of using the Wayflow endstation. Regrowth of the surface amorphous layers produced by these changes did not result in the formation of shear type dislocation loops. Further annealing of the 100 keV Wayflow implant and the 190 keV 77K implant at 900°C for 30 minutes resulted in the formation of small prismatic extrinsic dislocation loops beneath the location of the original amorphous/crystalline interface (catagory II defects).[71]
Role of Implant Energy on Defect Structures for Phosphorus Implanted Silicon
Authors: Prussin S. , Jones Kevin S.
Published: March 2011

A series of 18 wafers were implanted with phosphorus ions covering an energy range of 25 to 180 keV at a dose of 1 × 1015 cm−2 using a Waycool end station which provides good contact between the wafers and a thermal sink. Half the wafers had {100} surfaces and the other half {111} surfaces. The morphology of the as-implanted surface, defined by the thickness of the amorphous layer and whether that layer was submerged or lay at the surface, was affected by implant energy and surface orientation. After a 550°C regrowth and an activation anneal of 30 minutes at 900°C, the defect structures were evaluated by plan and cross-sectional transmission electron microscopy. A dear correlation was found between the implant morphology, the wafer orientation, and the defect structures.
Deep-Levels Associated with Implanted Titanium in Silicon
Authors: Ransom Craig M. , Iyer S.S.
Published: March 2011

Titanium was ion implanted at 180 KeV into p-type silicon to form a buried TiSi2 layer. DLTS measurements of n+p junctions have shown two minority carrier traps at Ec − Et = 0.24 and 0.51 eV. Also, a single majority trap at Ev + Et = 0.41 eV was observed. The concentrations of these levels were calculated to be approximately 1013 cm−3. DLTS measurements of low-fluence 50 KeV Ti implantations using Schottky diodes showed four levels dependent on silcon type.
Amorphization of Silicon by Boron Ion Implantation
Authors: Shih Y. , Washburn J. , Gronsky R. , Weber E.R.
Published: March 2011

Amorphization of silicon due to implantation of boron ions which is the lightest element used for I.C. fabrication processes, has been systematically studied for various temperatures, voltages and dose rates. A model for formation of amorphous silicon by light ion implantation is proposed. It is suggested that accumulation of point defects and/or clusters is required at the initial stage of amorphization process. Diinterstitial -divacancy pairs are suggested to be the embryos of amorphous zones formed during implantation at room temperature. Out -diffusion of highly mobile interstitials during amorphization is thought to explain differences in the critical energy for amorphization with low and high energy implantation at liquid nitrogen temperature.
Application of The Silicon Interstitial Based Intrinsic Gettering Process to the Formation of Multilevel Defect Structures
Authors: Nauka K.
Published: March 2011

The new intrinsic gettering mechanism based on the interactions of silicon interstitialshas been studied in float zone silicon with virtually zero oxygen content. Silicon wafers were subjected to the high-low-medium temperature annealing cycle, with the high temperature step carried out subsequently in an inert ambient, followed by the dry 02, followed by an inert ambient. The annealing caused formation of a multilevel structure consisting of two defect free regions with a high lifetime value, separated by a layer with high defect density and a low lifetime value. The experimental data corresponds to the theoretical calculations describing silicon interstitial injection during dry 02 oxidation and their diffusion during annealing in an inert ambient.
Interfacial Tunnel Structures In Cmos Source/Drain Regions Following Selective Deposition of Tungsten
Authors: Deblasi J.M. , Sadana D.K. , Norcott M.H.
Published: March 2011

The influence of B and As ion implantation on the location and density of interfacial tunnels, the extent of lateral encroachment, the amount of silicon consumed, and the crystallographic defects in CMOS source/drain structures following selective chemical vapor deposition of tungsten has been characterized.
Correlation Between Ti-Silicided Shallow Junction Diode Leakage and Titaniun Diffusion during TISI2 Fornation
Authors: Nauka K. , Amano Jun , Scott M.P. , Weber E.R. , Turner J.E. , Tsai R.
Published: March 2011

Deep level transient spectroscopy (DLTS) in conjunction with other analytical techniques was used to establish a correlation between the leakage current in the TiSi2/p+/n-Si shallow diodes (0.25 micron) and the Ti-related Ec - 0.23 eV deep trap. It was found that Ti diffused into the junction region durin the TiSi2 formation and caused leakage currents with values up to 2 × 10−8 A/cm2. Further increases of the leakage current were related to the formation of a TiSi2/n-Si Schottky barrier.
Effectiveness of CVD thin Film Backside Gettering and Its Interaction with Intrinsic Gettering
Authors: Wong C.-C. D. , Hahn S. , Ponce F. A. , Rek Z. U.
Published: March 2011

The effectiveness of CVD thin film backside gettering on n-type CZ silicon wafers for CMOS technology has been investigated using optical techniques for bulk microdefect analyses and transmission electron microscopy for interfacial structure study. The deposition of LPCVD polysilicon (500-2000 nm), silicon nitride (150 nm), or poly/nitride films on the backside of Si wafers was found to enhance the bulk precipitation. Bulk microdefect density increased as the thickness of polysilicon increased. At the polysilicon/silicon interface, no extended line defects from polysilicon were observed. Based on the results of minority carrier lifetime and oxide breakdown measurements, the best gettering efficiency was given by 1300 nm polysilicon backside gettering scheme.
Microstructure and Resistivity OFCr75 Si25 Thin Films
Authors: Weiss B. Z. , Tu K. N. , Smith D. A.
Published: March 2011

The electrical and microstructural changes of initially amorphous Cr75Si25 thin coevaporated alloy films have been studied as a function of temperature from room temperature to 950°C. Crystallization occurs in two stages. In the “primary” stage the major portion of the amorphous film crystallizes and a steep drop in resistivity occurs. In the “secondary” stage the amorphous residue crystallizes and is accompanied by a further gradual decrease in resistivity. The resistivity depends linearly on the volume fraction Vτ(t) crystallized to give Cr3Si only for Vτ(t) < 0.35.
Furnace Annealed Thin Films of Plasma Enhanced Chemical Vapor Deposited Titanium Borides on Silicon
Authors: Williams L. M.
Published: March 2011

Thin films of titanium borides, deposited onto silicon substrates at 600 °C using plasma enhanced chemical vapor deposition, were annealed in a furnace at temperatures from 700 °(C to 990 °C. Structural properties and electronic properties were measured for the annealed films and the asdeposited films for comparison. Sheet resistances for the films show about a 35% decrease after anneals at 990 °(C. The reduction in sheet resistance appears to be relatively insensitive to the length of the anneal time. X-ray diffraction spectra of the as-deposited films show no peaks that are attributable to crystalline titanium borides; however, there are diffraction peaks that are believed to be caused by products from reactions between the titanium borides and the silicon substrate during deposition. There is evidence that crystalline titanium diboride may start to form during the anneal at 990 °C.
Electrical Characterization of ZrN
Authors: Krusin-Elbaum L. , Brodsky S. , Ahn K.
Published: March 2011

We have investigated reactively sputter',d ZrN, the most thermally stable of the refractory metal nitrides, for its applicability as a submicron gate electrode. One would require for such gate electrode in addition to the lowest possible resistivity, a metal work function that will tailor the threshold voltage of metal/oxide/semiconductor (MOS) field effect transistor in such a way as to minimize the channel implant. Having these requirements in mind, we have measured the temperature dependence of resistivity, its dependence on the annealing temperature and work function of ZrN films. Our best films have resistivity, p of 20 A2-cm, comparable to TiSi. We find that p of as-deposited films being nearly stoichiometric, decreases about 20% after 1000°C anneal. Such anneal does not significantly alter the average grain size, which remains about 300 A even at this temperature. The temperature dependence of p at low temperatures indicates phonon scattering mechanism and we suggest that small amounts of oxygen are re- sponsible for residual resistance. The films undergo superconducting transition at 7.5-8 K and this transition provides an additional check on the compositonal homogeneity of the films. The work function, determined from the capacitance-voltage (C-V) characteristics of ZrN capacitors with various thicknesses of Si02, has value 0. = 4.6 Volts, at the midgap between n+ and p+ polysilicon and thus is applicable to 0.5 1m N-MOS and submicron C-MOS.
An Analysis of Conventional and Self-Aligned four Terminal Resistor Structures for The Determination of The Contact Resistivity from End Resistance Measurements
Authors: Suni I. , Finetti M. , Grahn K.
Published: March 2011

A computer model based on the finite element method has been applied to evaluate the effect of the parasitic area between contact and diffusion edges on end resistance measurements in four terminal Kelvin resistor structures. The model is then applied to Al/Ti/n+ Si contacts and a value of contact resistivity of Qc = 1.8×10−7.Ωcm2 is derived. For comparison, the use of a self-aligned structure to avoid parasitic effects is presented and the first experimental results obtained on Al/Ti/n+Si and Al/CoSi2/n+Si contacts are shown and discussed.
Laser Induced Metal and Alloy Plating with Simultaneous Silicide Compound Formation
Authors: Zahavi J. , Tamir S. , Halliwell M.
Published: March 2011

Highly selective metal and alloy deposition with simultaneous silicide formation - on semiconductor substrates immersed in commercial electroplating solutions has been investigated via pulse laser irradiation without masking procedures and external electric current.

Specimens of 5i and GaAs substrates, immersed in gold and in palladiumnickel electroplating solutions, were irradiated by a Qswitch YAG pulse laser perpendicular to their surfaces at predesired local zones. The gold, palladium and nickel deposits thus obtained were subsequently examined and characterised by SEM, TEM, AES, ESCA and RBS.

Deposit thickness ranged from a few hundred angstroms to several micrometers, depending primarily on the laser irradiation energy. The elemental Gold deposit exhibited Schottky barrier contacts with the GaAs and Si substrates. Palladium and nickel silicides obtained on n-type silicon substrates likewise exhibited Schottky behavior contracts.
Rapid Thermal Processing and The Quest for Ultra Shallow Boron Junctions
Authors: Sedgwick Tom
Published: March 2011

Rapid Thermal Processing (RTP) can minimize processing time and therefore minimize dopant motion during annealing of ion implanted junctions. In spite of the advantage of short time annealing using RTP, the formation of shallow B junctions is thwarted by channeling, transient enhanced diffusion and concentration enhanced diffusion effects all of which lead to deeper B profiles. Channeling and transient enhanced diffusion can be avoided by preamorphizing the silicon before the B implant. However, defects at the original amorphous/crystal boundary persist after annealing. Very low energy B implantation can lead to very shallow dopant profiles and in spite of channeling effects, offers an attractive potential shallow junction technology. In all of the shallow junction formation techniques RTP is required to achieve both high activation of the implanted species and minimal diffusion of the implanted dopant.
Using Rapid Thermal Processing to Induce Epitaxial Alignment of Polycrystalline Silicon Films on (100) Silicon
Authors: Harrison H.B. , Johnson S.T. , Komem Y. , Wong C. , Cohen S.
Published: March 2011

Undoped polycrystalline silicon (poly-Si) films obtained by low pressure chemical vapour deposition (LPCVD) techniques have previously been demonstrated to align epitaxially with respect to the underlying (100) silicon substrate in the 1000-1100°C temperature regime. However the alignment rate at temperatures in excess of 1100°C is too rapid to be obtained by conventional furnace processing. Rapid Thermal Processing (RTP) offers an excellent technique of attaining this temperature in the requisite time and in this paper we report on the results of a study in which RTP has been used. Our results show an activation energy of ∼4.5eV, and that the growth rate constant is dramatically enhanced, without any alignment delay in the initial heat treatment phase, which is contrary to previous findings.
Effects of Pre-Gate Oxidation Cleaning and Gettering Upon The Very Thin Oxide Integrity
Authors: Lee J. , Tung C. Y. , Hahn S. , Chiao P.
Published: March 2011

Various pre-gate oxide cleaning and gettering techniques on the integrity of thin gate oxide were investigated. A 100 Å thick oxide capacitor was used to study its time-dependent breakdown characteristics and minority carrier lifetime. It has been shown that the oxide integrity as measured by time-dependent breakdown and the minority carrier lifetime are very sensitive to the cleaning technique. On the other hand, given adequate cleaning process, different intrinsic gettering schemes may only influence the oxygen precipitation, as well as the minority carrier lifetime, but not the oxide integrity.
The Influence of Point Defects on Two Dimensional Diffusion Kinetics
Authors: Griffin P.B. , Plummer J.D.
Published: March 2011

The problems associated with two-dimensional diffusion of impurities coupled with point defects are outlined. The relative importance of the generation, diffusion and surface recombination rates are examined and the implications for 2-D modelling are discussed. Experimental results for the diffusion coefficient of interstitials indicate that the point defects can have orders of magnitude faster diffusivity than dopants. For accurate 2-Dprofiles, a large simulation space is needed to solve for the defects even though the impurity diffusion of interest occurs in the near surface region. The lateral extent of the diffusion profile is determined by the surface recombination rates of the defects. Results indicate that different technologically important interfaces, such as nitride and pad oxide have different recombination rates. The time dependence of the lateral decay isexperimentally investigated and indicates a steady state condition being reached. Parameters are extracted for the 2-D process simulator SUPREM-IV and the computer simulations are compared with experiment.
Synthesis and Sintering Comparison of Cordierite Powders
Authors: Bernier J. C. , Rehspringer J. L. , Vilminot S. , Poix P.
Published: March 2011

Cordierite and cordierite based glass ceramics are promising materials for electronic packaging. Preparations by organic and inorganic precursors along sol-gel processing are reported. Compared with conventional methods, they show a drastic decrease of the sintering temperatures. A process able to giving better than 95% theoretical density ceramic below 1000°C, with good electronic properties is described.
Synthesis and Processing of the Sol-Gel Derived β-Quartz Lithium Aluminum Silicates
Authors: Covino J. , Laat F. G. A. De , Welsbie R. A.
Published: March 2011

Lithium Aluminum Silicate (LAS) glass-ceramic compositions with and without phosphorous have been synthesized by Sol-Gel techniques. Resulting LAStype powders are herein designated as NZ and NZP. X-Ray analysis, thermogravimetric analysis (TGA), particle size measurements, and thermal dilatometric shrinkage measurements have been performed on these samples. The NZ and NZP powders in calcined form, as well as commercially-available LAS glass-ceramic produce x-ray diffraction pattern very similar to the pattern of Virgilite LixAlxSi3−xO6 (x=0.5–1.0). There is little difference between powders with and without phosphorous in the diffuse reflectance spectra (DRS). Preliminary results show that the material can be easily processed into glass ceramics.
A Solid State Multinuclear Magnetic Resonance Study of the Sol-Gel Process using Polysilicate Precursors
Authors: Klemperer W. G. , Mainz V. V. , Millar D. M.
Published: March 2011

A solid state multinuclear NMR study of the sol-gel process was performed using the molecular building blocks tetramethoxysilane, hexamethoxydisiloxane, octamethoxytrisiloxane and octamethoxyoctasilsesquioxane as precursor monomers. Water content, solvent content, and hydrolysis/condensation processes were monitored using 17O, 13C, and 29Si FT, FTMAS and CPMAS NMR techniques.
High field 1H NMR Studies of Sol-Gel Kinetics
Authors: Kay Bruce D. , Assink Roger A.
Published: March 2011

High resolution 1H NMR spectroscopy at high magnetic fields is employed to study the reaction kinetics of the Si(OCH3)4:CH3OH:H2O sol-gel system. Both the overall extent of reaction as a function of time and the equilibrium distribution of species are measured. In acid catalyzed solution, condensation is the rate limiting step while in base catalyzed solution, hydrolysis becomes rate limiting. A kinetic model in which the rate of hydrolysis is assumed to be independent of the adjacent functional groups is presented. This model correctly predicts the distribution of product species during the initial stages of the sol-gel reaction.
Stereo-Tem Imaging of Sol-Gel Glass Surfaces
Authors: Ruben George C. , Shafer Merrill W.
Published: March 2011

Sol-gel top and cross-fractured surfaces have been Pt-C replicated (9.7–11.3 Å thick) and carbon film backed (100–145 Å thick) and separated from the gel with an HF solution. Samples made from both base catalyzed LUDOX/Kasil mixtures and acid catalyzed alkoxides were studied with tilt series of 104 to 105 magnification TEM mlcrographs of the surface replicas. The LUDOX/Kasil gels contained spherical particles with a raspberry-like morphology and the acid catalyzed alkoxIdes are composed of densely packed filaments and no apparent particles. The smallest structural entity in both gels are Pt/C coated filaments (12–14Å) estimated to be 1.5–2.7 Å in width. The pore sizes were characterized in both gel types, though TEM pore measurements were only made on the LUDOX/Kasil gels.
Drying Mechanics of Gels
Authors: Scherer George W.
Published: March 2011

A model is presented for the stresses and strains that develop in a gel during drying. The driving force for shrinkage is assumed to be the interfacial energy, and the gel is considered to be viscoelastic. The liquid seeks to flow into the dry region of a gel in order to replace the solid-vapor interface with a solid-liquid interface having lower specific energy. This creates a “redistribution pressure” that causes the wet region to contract. The free contraction rate can be calculated by equating the decrease in surface energy with the energy dissipated in viscous flow as the gel contracts. The permeability of the gel to the liquid in the pores is especially important in the early stages of drying, and may control the contraction rate. The model allows quantitative predictions of contraction rate and stress during drying. In this paper, the model is applied to a plate drying from both sides.
Calculated Vs Measured Viscosities of Sol-Gel Processed Silica
Authors: Gallo T. A. , Klein L. C.
Published: March 2011

The densification of sol-gel processed silica was studied by comparing calculated and measured viscosities between 700 and 850°C. Linear shrinkage was measured in a dilatometer. From shrinkage data, relative bulk densities were determined. The densities were used in a model for viscous sintering to calculate viscosities. Beam-bending viscosimetry was used to determine viscosities directly. The deflection rate of a centrally loaded beam was measured. Both the calculated and measured viscosities had the same time dependence. The temperature dependence was also determined.
Fluorine In Silica Gels
Authors: Rabinovich E. M. , Wood D. L.
Published: March 2011

Fluorine has a remarkable and diverse action in silica sols, gels and gel-derived glasses. Introduced in ionic form, it causes more rapid gelation, it reduces surface area and water adsorption of dry gels, and it helps to eliminate bubble formation during sintering and reheating of gel-derived glasses. The mechanisms for these actions of the fluoride ion are reviewed, with a more detailed discussion of the rate of gelation. Several previously held views of the way fluoride accelerates gel formation are compared with a new suggestion that it is caused by an electrostatic attraction between the proton of the OH of silicic acid and F− present as Si-F groups.
Studies of the Initial Steps in Sol-Gel Processing of Si(OR)4:29Si NMR of Alkoxysilane and Alkoxysiloxane Solutions
Authors: Balfe Carol A. , Martinez Sheryl L.
Published: March 2011

Silicon-29 NMR has been used to investigate the initial steps of hydrolysis and condensation of tetramethoxysilane (TMOS), hexamethoxydisiloxane, and octamethoxytrisiloxane in both basic and acidic methanol solutions. Comparisons of the spectra obtained from the various starting solutions and literature reports of mono-, di-, and tri-silicic acids in aqueous solution were used to identify and assign chemical shifts to condensation intermediates in the TMOS system. The observation of cyclic intermediates in the acid catalysis of TMOS in methanol and the chemical shifts of several products of its hydrolysis and condensation are reported.
General Scaling Phenomena in Porous Silica Gels as Probed by Saxs and Molecular Adsorption (Tiling)
Authors: Drake J. M. , Levitz P. , Sinha S.
Published: March 2011

Using N2 adsorption (B.E.T.), small angle X-ray scattering and molecular adsorption (tiling) we attempt to describe the internal pore morphology and surface structure of three porous silica gels. The results are analyzed from both a classical euclidian and a fractal scaling viewpoint. The applicability of both viewpoints are shown to be limited but important in describing the structure of porous silicas.
Packings of Uniform Disks Having Bond Orientational Order
Authors: Onoda George Y.
Published: March 2011

Packings of uniform disks with bond orientational order (BOO) are described. These are distinct from both ordered structures, that have translational correlations as well as BOO, and fully disordered structures that lack both features.
Studies of Organometallic Precursors to Aluminum Nitride
Authors: Interrante Leonard V. , Carpenter Leslie E. , Whitmarsh Christopher , Lee Wei , Garbauskas Mary , Slack Glen A.
Published: March 2011

The reaction of trialkylaluminum compounds with ammonia has been examined as a potential route to high purity AlN powder and to AlN thin films. This reaction proceeds in stages in which the initially formed Lewis acid/base adduct undergoes thermal decomposition to a series of intermediate alkylaluminum-amide and -imide species with increasing Al-N bonding, i.e.,

The structure and properties of several of these species have been studied using various physical and chemical methods, leading to a better understanding of the chemistry of this novel AlN precursor system. The structure of the intermediate organoaluminum amide, (CH3)2AlNH2, has been determined by single crystal X-ray diffraction methods and found to contain molecular trimer units with a six-membered Al-N ring structure similar to those which make up the wurzite structure of AlN. This compound is readily volatile and has been used to deposit AIN thin films on Si surfaces by a low-pressure CVD process. This approach has also been used to prepare AlN as a high surface area, high purity powder.
A Low Temperature Chemical Route to Precursors of Boride and Carbide Ceramic Powders
Authors: Ritter Joseph J.
Published: March 2011

The controlled reductive dehalogenation of elemental halides has been studied as a low temperature approach to boride and carbide precursors. We have shown that SiCl4 and CCl4 can be reacted with metallic sodium at 130° in a non-polar solvent to give the precursor to SiC. Similar type reactions with TiCl4 and BCl3 or with BCl3 and CC14 have produced the precursors to TiB2 and B4C respectively. This procedure has also been used to generate the precursors to the two-phase composites SiC/TiC and SiC/TiN. The method is generally applicable to any combination of elemental halides which can be reduced by alkali metals or alkali metal alloys.
A New Catalytic Method for Producing Preceramic Polysilazanes
Authors: Blum Yigal D. , Laine Richard M. , Schwartz Kenneth B. , Rowcliffe David J. , Bening Robert C. , Cotts David B.
Published: March 2011

A transition metal (e.g., Ru3 (CO)12, Pt/C) catalyzed process for Si-N bond formation is discussed that provides a new route to mono-, oligo-, and polysilazanes. The catalysts function by activating Si-H bonds in the pres-ence of ammonia. Polymeric silazanes can also be produced from oligomers in the presence of ammonia at low temperatures. This method allows us to control or modify the composition of the polysilazane during or after the polymeriza-tion. A variety of polysilazanes were prepared and converted to Si3 N4 with ceramic yields ranging from 55%-85%. By varying the monomers and reaction conditions, we can control the nitrogen and carbon content in the preceramic polymers, which enables us to obtain ceramic products that are primarily Si3N4and simultaneously minimizes the coproduction of SiC and C.
A Comparison of Structures and Crystallization Behavior of Gels, Gel-Derived Classes and Conventional Glasses
Authors: Mukherjee Shyama P.
Published: March 2011

Studies on the structures and crystallization behavior of gels in TiO2, GeO2, SiO2-GeO2 and PbO-GeO2 systems are presented to analyze the differences in structures and crystallization behavior of gel-derived glasses and conventional glasses. The kinetic parameters for crystallization such as activation energies and frequency factors of gels, gel-derived glasses and conventional glasses in the GeO2-PbO system are presented to elucidate their difference in nucleation and crystallization behaviors. The influence of gel processing parameters such as pH and water concentration on the crystallization behavior of gels are discussed.
Synthesis and Characterization of Aluminum Propionate Sol-Gel Derived Al2O 3
Authors: Covino J. , Nissan R. A.
Published: March 2011

Al2O3 has been synthesized from aluminum propionate [A1(CO2CH2CH3)3] bySol-Gel techniques. Methods of characterization include: x-ray powder diffraction, scanning electron microscopy (SEM) and nuclear magnetic resonance(NMR). Solution and solid state 13C and 27Al NMR data is coupled with bothx-ray diffraction powder data and SEM in order to understand the transitionfrom sol + gel + amorphous powder + crystalline powder In the sonicated andunsonicated aluminum propionate precursor, and A12O3 powders. Resultsindicate that the sonicated dried powder is crystalline, having the γA12O3structure while the unsonicated dried powder is amorphous and crystallizesat 800°C with the a A12O3 structure. These differences in crystallinity arefurther substantiated by solid state 27AL NMR chemical shifts and linewidths at half height.