bluuebunny/crossref_metadata_2025_split huggingface dataset:
Low Temperature Oxynitridation of SiGe in NO/N2O Ambients
Authors: Dasgupta Anindya , Takoudis Christos G. 
Published: March 2017

AbstractX-Ray photoelectron spectroscopy (XPS), secondary ion mass spectroscopy (SIMS) and spectral ellipsometry have been used to study sub-35 Å low temperature oxynitrides of SiGe. The oxynitridations steps have been performed at 550°C and 650°C, while the oxynitridation feed gases have been preheated to 900°C and 1000°C, respectively, before entering the reaction zone. XPS and SIMS data suggests that NO-assisted oxynitridation incorporates more nitrogen than the N2O-assisted one, while there is minimal Ge segregation towards the dielectric/substrate interface in both oxynitridation processes. SIMS data suggests that the nitrogen is distributed throughout the film in contrast to high temperature Si oxynitridation where nitrogen incorporation takes place near the dielectric/substrate interface. Spectral Ellipsometry has been used to measure the final thickness of the oxynitrides film. These results are discussed in the context of an overall mechanism of the oxynitridation of SiGe.
PECVD Silicon Nitride for Damascene Applications
Authors: Lee Albert , Rajagopalan Nagarajan , Le Maggie , Kim Bok Heon , M'Saad Hichem 
Published: March 2017

AbstractA Pecvd silicon nitride film, Damascene Nitride™, is deposited in a PECVD chamber with a hollow cathode faceplate using silane and ammonia as precursor gases. Various techniques (FTIR, RBS-HFS, SIMS, TDS and BTS) were used to characterize the structure, composition, density and wet etch rate of the film. FTIR analysis indicates that Damascene Nitride is very similar to a high density plasma (HDP) nitride film. HFS analysis shows the film's hydrogen content to be 13%,∼6% less than other PECVD nitride films, leading to a 20% improvement in etch selectivity to FSG. The film wet etch rate is 2 times slower than that of other PECVD nitrides, and the dielectric constant k was measured to be 6.8, which is lower compared to other PECVD nitrides and HDP CVD nitrides where k∼ 7.0 and 7.5, respectively. SIMS analysis shows that Cu diffusion is <250Å in the nitride, and low leakage current (10-10 A) is confirmed through BTS testing. The higher density of Damascene Nitride leads to higher etch selectivity and better Cu barrier properties, allowing a thinner nitride film to be used. Thinner nitride layers, in addition to the lower k of Damascene Nitride, leads to a 5-6% reduction in RC delay when Damascene Nitride is used with low k dielectric materials.
Passivation of Defect States in Amorphous and Crystalline Si by use of Cyanide Treatment and Improvement of Solar Cell Characteristics
Authors: Kobayashi Hikaru , Fujiwara Naozumi , Fujinaga Tetsushi , Niinobe Daisuke , Maida Osamu , Takahashi Masao 
Published: March 2017

AbstractWe have developed a new method of eliminating defect states in Si. This method called cyanide treatment simply includes immersion of Si in KCN solutions followed by the rinse. The contamination by potassium ions can be completely prevented by the inclusion of 18-crown-6 in the KCN solutions (crown-ether cyanide treatment). When the crown-ether cyanide treatment was performed on intrinsic amorphous Si (a-Si) films, decreases in the photo-and dark current densities with the irradiation time were completely prevented. When cyanide treatment using aqueous KCN solutions was applied to pin-junction a-Si solar cells, the conversion efficiencies measured before and after light-induced degradation became higher than those with no treatment. These improvements are attributed to the elimination of defect and defect precursor states by the reaction with cyanide ions, resulting in the formation of Si-CN bonds. From density functional calculations, Si-CN bonds are found to possess a high bond energy of 4.5 eV. Due to the high bond energy, the bonds are not ruptured by heat treatment at 800°C and upon irradiation, resulting in the thermal and irradiation stability of the cyanide treatment.
Temperature and Frequency Dependencies of Charging and Discharging Properties in Mos Memory Based on Nanocrystalline Silicon Dot
Authors: Huang Shaoyun , Banerjee Souri , Oda Shunri 
Published: March 2017

AbstractTemperature and frequency dependencies of the electrical properties of SiO2/nanocrystalline Si (nc-Si)/SiO2 sandwich structures have been studied. A clear positive shift in capacitance-voltage (C-V) and conductance-voltage (G-V) characteristics suggests electron trapping in nc-Si dots. The role of interface states and deep traps in these devices has also been examined, which shows that they have little effect on the overall device performance.
Amorphous Silicon Vertical Thin Film Transistor for High Density Integration
Authors: Chan Isaac , Nathan Arokia 
Published: March 2017

AbstractThis paper presents a fabrication process for vertical thin film transistors (VTFT) based on hydrogenated amorphous silicon (a-Si:H) technology. This process yields VTFTs with an ON/OFF ratio of 105 and a leakage current of the order of 10-13A for a channel length of 1 μm. The device structure, because of significant undercutting formed after dry-etch process (reactive ion etching or RIE), has a channel profile that is skewed as opposed to vertical. This serves to compromise the structural integrity and the electrical performance of the device. Therefore, an anisotropic dry-etch process for this channel profile is being developed. It is found that a CF4/20%H2 gas mixture yields a sharp vertical sidewall profile. In addition, a modified masking process has been developed to produce a rectangular photoresist profile so as to achieve an anisotropic etch profile for the channel region. The effects of the photoresist geometry on the anisotropic dry-etch process will be discussed.
High Voltage Amorphous Silicon Solar Cells by Hot-Wire Chemical Vapor Deposition
Authors: Wang Qi , Iwaniczko Eugene 
Published: March 2017

AbstractWe have achieved the best open-circuit voltage (Voc = 0.94 V) to-date in hydrogenated amorphous silicon (a-Si:H) photovoltaic cells deposited entirely by hot-wire chemical vapor deposition. The fill factor (FF = 0.74) remained high and a current density of 8-9 mA/cm2 with about 1800 Å i-layer was obtained in our n-i-p cells on untextured stainless-steel substrates. The Voc improvement of about 60 mV in compared to our previous best Voc was obtained by incorporating materials grown with H-dilution close to the phase transition from amorphous to microcrystalline silicon in the i-layer and at the i-p interface. A low substrate temperature of 150°C for the i-layer was also essential, most likely to widen the bandgap of the i-layer. A brief atomic H-treatment after grown the i-layer increases the Voc further by improving the p-i interface. The last 60 Å of the i-layer before p-layer is extremely close to the transition to microcrystallinity, though it remains mainly amorphous. Our p-layers are also close to the phase transition.
Charge-trapping Metastability in p-Type Hydrogenated Amorphous Silicon: Meyer-Neldel Rule and Entropy Change
Authors: Crandall Richard S. 
Published: March 2017

AbstractMeasurements of capacitance transients due to charge carrier emission from metastable defects in p-type hydrogenated amorphous silicon (a-Si:H) p/n junction structures, show that both holes and electrons can be metastably trapped in the p layer. At 350 K electrons and holes are emitted at the same rate defining the isokinetic temperature (Tiso) for the Meyer-Neldel rule. The enthalpy changes for hole and electron emission are 0.94 and 0.51 eV, respectively. The entropy changes for hole and electron emission are 31 and 16 Boltzmann constant, respectively. Charge emission rates are measured, for the first time, above and below Tiso. Below Tiso electrons are emitted faster than holes and above Tiso the reverse is true. These relative changes in emission rates are a direct consequence of the large entropy changes in the defect reactions. Tiso, within experimental error is the same as the H glass equilibration temperature (360 K) measured by others in p-type a-Si:H, suggesting that the defect reactions measured here are involved in H glass equilibration. Activation and deactivation of B atoms with accompanying charge emission likely govern both processes.
On the Surface Roughness Evolution During a-Si:H Growth
Authors: van de Sanden M.C.M. , Smets A.H.M. , Kessels W.M.M. 
Published: March 2017

AbstractThe surface roughness evolution during a-Si:H film growth from a SiH3 beam under purely chemical deposition conditions is discussed. The data is explained in terms of the different universality classes proposed in literature. It is argued that roughness evolution during a-Si:H growth shows great similarity with MBE growth, which belongs to a universality class studied extensively by Das Sarma and coworkers. The activation energy for surface diffusion extracted from simulating the growth exponent β vs. temperature reveals an activation energy of about 1 eV. This result suggests that the surface roughness evolution is not controlled by the weakly adsorbed SiH3 radical.
The Use of Seed Layers in Hot Wire Chemical Vapor Deposition of Microcrystalline Silicon Films
Authors: Zaharias G.A. , Mahan A.H. , Schropp R.E.I. , Xu Y. , Williamson D.L , Al-Jassim M.M. , Romero M.J. , Gedvilas L.M. 
Published: March 2017

AbstractThe effect of thin seed layers on the subsequent growth of thick, high growth rate bulk μc-Si is investigated by XRD, SEM and cross sectional TEM. All layers were deposited by hotwire chemical vapor deposition (HWCVD). When the seed layer as observed by XRD is highly crystalline, made by using high H2 dilution (H2:SiH4 100:1), the amorphous incubation layer typical of μc-Si growth is virtually eliminated. Furthermore, with this seed layer, bulk layer deposition conditions that would otherwise produce highly amorphous material enable a composite film with significant crystallinity. When the seed layer is predominantly amorphous, made using a much lower H2 dilution (10:1), there is evidence that very small crystallites, undetected by XRD, still facilitate immediate nucleation and enable the formation of larger grains in the subsequent bulk layer. In concurrence with other HWCVD results, lowering the filament temperature results in significant improvements in film compactness, photoresponse and grain size, while maintaining significant crystallinity. Such films have been incorporated into high deposition rate solar cells.
Amorphous to Microcrystalline Transition in Thickness-graded Hot-Wire CVD Silicon Films
Authors: Wang Qi , Perkins John , Moutinho Helio , To Bobby , Branz Howard M. 
Published: March 2017

AbstractWe study the amorphous to microcrystalline silicon phase transition in hot-wire chemical vapor deposition thin-film silicon by depositing a series of unique, thickness-graded, samples on a glass substrate at 200°C. By inserting or withdrawing a motor-driven shutter during growth, we make samples that vary from 200 to about 2000 Å thick across each 5-cm along stripe. Each stripe is grown at a different dilution ratio of hydrogen to silane in the source gas. The phase composition at various locations was determined by Raman and ultraviolet-reflectivity measurements. Atomic force microscopy (AFM) images of topology reveal that the surface changes from a rather smooth a-Si phase to more granular microcrystalline-Si (rms roughness increases from 10 to 47 Å).
Epitaxial Growth in Dislocation-Free Strained Alloy Films
Authors: Huang Zhi-Feng , Desai Rashmi C. 
Published: March 2017

AbstractThe morphological and compositional instabilities in the heteroepitaxial strained alloy films have attracted intense interest from both experimentalists and theorists. To understand the mechanisms and properties for the generation of instabilities, we have developed a nonequilibrium, continuum model for the dislocation-free and coherent film systems. The early evolution processes of surface pro.les for both growing and postdeposition (non-growing) thin alloy films are studied through a linear stability analysis. We consider the coupling between top surface of the film and the underlying bulk, as well as the combination and interplay of different elastic effects. These e.ects are caused by filmsubstrate lattice misfit, composition dependence of film lattice constant (compositional stress), and composition dependence of both Young's and shear elastic moduli. The interplay of these factors as well as the growth temperature and deposition rate leads to rich and complicated stability results. For both the growing.lm and non-growing alloy free surface, we determine the stability conditions and diagrams for the system. These show the joint stability or instability for film morphology and compositional pro.les, as well as the asymmetry between tensile and compressive layers. The kinetic critical thickness for the onset of instability during.lm growth is also calculated, and its scaling behavior with respect to misfit strain and deposition rate determined. Our results have implications for real alloy growth systems such as SiGe and InGaAs, which agree with qualitative trends seen in recent experimental observations.
Computational Modeling of Homogeneous Nucleation and Particle Growth During Chemical Vapor Deposition of Silicon Films from Silane Plasmas
Authors: Warthesen S , Bhandarkar U , Girshick S , Kortshagen U 
Published: March 2017

AbstractWe have been developing a model to study the nucleation and growth of particles in silane plasmas. Presently we are experimenting with parameters that could potentially be important. It has been found that an increase in the heavy species gas temperature leads to a delay in the nucleation of particles in low pressure silane plasmas. This effect could be useful in tailoring processes for the manufacture of new materials such as polymorphous silicon. We have made an effort to study this effect using a plasma chemistry model. The model includes gas temperature dependent electron attachment and vibrational relaxation of excited species with a view to study their importance in relation to the gas temperature. Preliminary simulation results predict that these two processes do not contribute substantially to slowing the nucleation process when the gas temperature is increased. Extra efforts must be made to study this potentially important effect.
Surface Roughness Evolution of PECVD Cathodic and Anodic a-Si:H.
Authors: Dalakos George T. , Plawsky Joel L. , Persans Peter D. 
Published: March 2017

AbstractSurface or interface roughness can impact optical, electronic, and MEMS applications of thin a-Si:H films. Deposition at lower temperatures can be advantageous for some applications of a-Si:H, but lower temperature deposition generally leads to rougher films. We have found that the evolution of surface roughness growth can be modified substantially by ion bombardment due to the self-bias of the plasma during Plasma-Enhanced Chemical Vapor Deposition (PECVD). Notable differences in the surface roughness evolution and deposition rate are shown for films deposited in “cathodic” versus “anodic” mode – where the substrate is placed on the powered and grounded electrode respectively. Suppression of surface roughness growth of a-Si:H can be achieved under conditions of relatively high ion bombardment even at deposition temperatures as low as 75 C. Atomic force microscopy (AFM) was used to measure the relative surface roughness profile as a function of deposition time. Analysis of the power spectral density of the roughness yielded important statistical surface parameter information. Based on these observations, insight is given into growth mechanisms under the two deposition conditions.
Microwave Plasma Assisted VHF-PECVD of Micro-Crystalline Silicon
Authors: Soppe Wim , Bailat Julien , Droz Corinne , Graf Urs , Kroll Ulrich , Meier Johannes , Shah Arvind 
Published: March 2017

AbstractGrowth of intrinsic micro-crystalline silicon layers by means of VHF-PECVD, assisted by remote microwave (MW) plasma has been investigated. The aim of the MW plasma is to enhance the deposition rate by introducing excited hydrogen and Ar atoms from the MW plasma in the VHF deposition zone. For this purpose a remote microwave plasma source was constructed in which a H2/Ar plasma is generated in a 20 mm diameter quartz tube. A gasshower has been constructed for homogeneous distribution of the flow of excited gas species from the microwave source into the deposition zone of the VHF-PECVD reactor where the dissociation of silane takes place. In a first series of experiments we applied high microwave power (< 500 W) and pure hydrogen in the MW source. This resulted in a larger deposition rate, but all layers – even grown at low silane concentrations – were amorphous and had a high oxygen content. The oxygen contamination was partly due to reduction of the quartz tube by the hydrogen plasma. In a second series of experiments Ar dilution and reduced MW power were used to eliminate the effect of etching of the tube by the microwave hydrogen plasma. In this series of experiments an increase of the growth rate of micro-crystalline silicon by about 15 % due to assistance of the microwave plasma was found. Optical emission spectroscopy indicates that – in these experiments – the main mechanism for the increased dissociation of silane is through molecular quenching reaction of Ar* metastables.
Effects of Substrate Temperature and Atomic Hydrogen Flow on the Mircocrystallinity of Evaporated Hydrogenated silicon Films
Authors: Stoltz A.J. , Mason Whitney , Benson J.D. , Dinan J.H. , McCormack K. , Kaleczyc A. 
Published: March 2017

AbstractAs a first step toward an understanding of the chemical and structural role of hydrogen in hydrogenated amorphous silicon, we utilized electron beam evaporation in an ultra high vacuum environment to deposit films of amorphous silicon and systematically dosed these films with atomic hydrogen during deposition. Secondary Ion Mass Spectroscopy (SIMS) data indicated that hydrogen concentration can be varied from the detection limit of SIMS to a value in excess of 1021 atoms cm-3. The intentional addition of hydrogen caused the concentration to fall from in an excess of 1021 atoms*cm-3 to below 1018 atoms*cm-3.
Magnetic Resonance Probes Of Band Tail States And Defects In Tetrahedrally Coordinated Amorphous Semiconductors
Authors: Taylor P. C. 
Published: March 2017

AbstractRecent electron spin resonance (ESR) results relating to (1) recombination processes for optically excited electrons and holes in tetrahedrally coordinated amorphous semiconductors and (2) kinetics of metastable defects (dangling bonds associated with the Staebler-Wronski effect) in hydrogenated amorphous silicon (a-Si:H). With regard to recombination processes, ESR measurements have been performed over a wide range of excitation intensities (nW/cm2 to W/cm2) on hydrogenated amorphous silicon (a-Si:H) and hydrogenated amorphous germanium (a-Ge:H). The kinetics can be studied down to carrier densities as low as 1014 cm-3. The longtime decay curves show that at large carrier separation (1) the random distribution of optically excited electrons and holes is subject to the condition of charge neutrality, and (2) the decays are universal and independent of the densities of localized, band-tail states. With regard to the metastable defects in a-Si:H, the kinetics of the production and thermal annealing of silicon dangling bonds have been measured at temperatures between 25 and 480 K using ESR. Below about 150 K the measurement of the dangling bonds is masked by long-lived, band tail carriers that accumulate with time. The production rate for silicon dangling bonds decreases with decreasing temperature and is nearly temperature independent below approximately 100 K. Defects created by 10 hours of irradiation below 100 K anneal almost completely at 300 K. In a- Ge:H, the first measurements of optically induced, metastable germanium dangling bonds have been made.
Generation-Recombination Noise in a-Si:H Studied by Device Simulations
Authors: Bakker J.P.R. , Capel P.J.S. van , Fine B.V. , Dijkhuis J.I. 
Published: March 2017

AbstractAn attempt is made to interpret low-frequency noise measured in a-Si:H n-i-n devices based on the assumption that the noise is due to generation-recombination (g-r) processes. The interpretation is based on a spatial distribution of recombination lifetimes of electrons obtained with the help from the AMPS-1D device simulation program. These lifetimes have the same order of magnitude as that of the noise observed. Further, a distribution of lifetimes naturally results from band bending. Simulations of noise spectra are obtained by multiplication of a phenomenological weight factor to the Lorentzian spectral contribution corresponding to the local electron lifetime. There are, however, two problems with this interpretation: (i) we were not able to come up with a reasonable noise description, where the relatively long electron lifetimes were not overshadowed by much shorter times (ii) the current description, where variance is included in a weight factor, is still incomplete, and therefore we can not explain the shape of the weight factor yet.
Lifetime Regime in the Electrically-Detected Transient Grating Method Applied to Amorphous and Microcrystalline Silicon Films
Authors: Sanguino P. , Niehus M. , Koynov S. , Brogueira P. , Schwarz R. , Conde J.P. , Chu V. , Schiff E.A. 
Published: March 2017

AbstractThe minority-carrier diffusion length in thin silicon films can be extracted from the electrically-detected transient grating method, EDTG, by a simple ambipolar analysis only in the case of lifetime dominated carrier transport. If the dielectric relaxation time, τdiel, is larger than the photocarrier response time, τR, then unexpected negative transient signals can appear in the EDTG result. Thin silicon films deposited by hot-wire chemical vapor deposition (HWCVD) near the amorphous-to-microcrystalline transition, where τR varies over a large range, appeared to be ideal candidates to study the interplay between carrier recombination and dielectric response. By modifying the ambipolar description to allow for a time-dependent carrier grating build-up and decay we can obtain a good agreement between analytical calculation and experimental results.
Transient Photocurrents in Microcrystalline Silicon Films
Authors: Reynolds Steve , Smirnov Vladimir , Main Charlie , Carius Reinhard , Finger Friedhelm 
Published: March 2017

AbstractTransient photoconductivity in microcrystalline silicon thin films prepared by VHF PECVD over a range of [silane]: [silane + hydrogen] concentrations γ from 3 to 6.3% has been measured as a function of temperature (210 K - 390 K) and laser pulse density (1013 – 1016 cm3). The behavior of highly crystalline films (γ ∼ 3%) bears certain similarities to n-type amorphous silicon, where the power law decay at long times is controlled by hole rather than electron kinetics. As γ approaches 6% the decay begins to resemble that of intrinsic amorphous silicon, consistent with structural studies which indicate a transition from crystalline to amorphous character. Transient photocurrent density of states spectroscopy on transitional films suggests a similar deep defect density to high-quality amorphous silicon, but a larger conduction band tail energy of some 30 meV and a tenfold increase in localised state density at a depth of about 0.4 eV.