bluuebunny/crossref_metadata_2025_split huggingface dataset:
Localised States in Microcrystalline Silicon Photovoltaic Structures Studied by Post-Transit Time-of-Flight Spectroscopy
Authors: Reynolds Steve , Smirnov Vladimir , Main Charlie , Carius Reinhard , Finger Friedhelm 
Published: June 2019

AbstractPost-transit time-of-flight spectroscopy has been used to study the density of states distribution in hot-wire CVD microcrystalline silicon pin solar cell structures. For an absorber layer Raman scattering intensity ratio ICRS of 0.4 or less, behaviour consistent with multiple-trapping carrier transport is observed and may be interpreted in terms of a conduction-band tail of some 18 meV slope plus a broad defect bump of order 1017 cm-3 centered at 0.55 eV relative to the mobility edge. As ICRS is increased beyond 0.4, the temperature-dependence of the photocurrent transient becomes inconsistent with multiple-trapping and above 0.6 the decays are almost temperature-independent. By comparing data taken at 300 K, it may be inferred from the multiple-trapping model that localised states between 0.35 and 0.5 eV are associated with the presence of columns or clusters of nanocrystals and those deeper than 0.5 eV with the amorphous tissue. Results are compared with previous work on coplanar and sandwich structures.
Helium Versus Hydrogen Dilution of Silane in the Deposition of Polymorphous Silicon Films: Effects on the Structure and the Transport Properties
Authors: Saadane O. , Lebib S. , Kharchenko A.V. , Suendo V. , Longeaud C. , Cabarrocas P. Roca i 
Published: June 2019

AbstractWe compare the deposition rate, hydrogen incorporation and optoelectronic properties of hydrogenated polymorphous silicon films produced either by the decomposition of silane-hydrogen or of silane-helium mixtures. Our results clearly show that He dilution allows to drastically reduce the RF power needed to achieve the same deposition rate as in the case of H2 dilution. Infrared spectroscopy and hydrogen effusion experiments show clear differences in the hydrogen bonding and content in both series of films. Interestingly, both He and hydrogen dilution result in films with improved transport properties, in particular the hole diffusion length, with respect to standard amorphous silicon. These results indicate that He dilution is a good alternative to H2 dilution to prepare intrinsic layers for solar cells.
Surface Roughness Study of Low-temperature PECVD a-Si:H.
Authors: Dalakos George T. , Plawsky Joel L. , Persans Peter D. 
Published: June 2019

AbstractSurface topography of a-Si:H thin films, deposited at 75°C by Plasma-enhanced Chemical Vapor Deposition (PECVD) has been examined using helium/silane feedstock mixtures under different substrate bias conditions. Notable differences in the surface roughness evolution are shown for films deposited in “cathodic” versus “anodic” mode – where the substrate is placed on the powered and grounded electrode respectively. Smooth and apparently featureless surfaces result from deposition on RF powered surfaces, upon which a self-bias induces high-energy ion bombardment. Rougher surfaces result from films deposited on electrically grounded surfaces. These anodic films show that after a transition period, surface roughness grows linearly with processing time, exhibiting mounded type growth as evidenced by 2-D power spectral density functions of surface height measurements. Linear growth in roughness has been predicted for shadow growth models assuming film precursor sticking coefficients of one and random angle approach of film precursor species. Growth of this nature has not been reported before in a-Si:H studies, which usually assume directional deposition conditions and sticking coefficients less than unity – occurring even at low processing temperatures.
Electrical and Optical Properties of Amorphous and Microcrystalline Hydrogenated Silicon Films Deposited Using Saddle Field Glow Discharge
Authors: Milostnaya I. , Allen T. , Gaspari F. , Kherani N.P. , Yeghikyan D. , Roes W.L. , Kosteski T. , Zukotynski S. 
Published: June 2019

AbstractAmorphous (a-Si:H) and microcrystalline (μc-Si:H) hydrogenated silicon films were obtained using DC saddle field glow discharge. The structure of the films was determined by Raman spectroscopy, SEM and TEM. The optoelectronic characteristics of both a-Si:H and μcSi:H were investigated using FTIR, UV/VIS spectroscopy, dark electrical conductivity (σd) and photoconductivity (σph) measurements. Boron and phosphorous doping of a-Si:H and μc-Si:H films was also investigated. The results show that both a-Si:H and μc-Si:H undoped films are highly resistive (σd=10-8-10-10 Ω-1cm-1). The doping efficiency of μc-Si:H films is much higher than a-Si:H films. The Tauc gap for a-Si:H was in the range 1.8-1.9 eV and for μc-Si:H films it was in the range 1.9-2.5 eV. The photoconductivity measurements of undoped films indicate a higher photosensitivity of a-Si:H films (σph/σd=104)than that of μc-Si:H films (σph/σd=10-100).
Properties of Nanocrystalline Germanium-Carbon Films and Devices
Authors: Niu X.J. , Dalal Vikram L. , Noack Max 
Published: June 2019

AbstractNanocrystalline Germanium-Carbon alloys, denoted by nc- (Ge,C):H, are a potentially useful new electronic material whose bandgap can be varied by changing the Ge:C ratios. We have shown previously that nanocrystalline (Ge,C):H films can be grown using remote ECR plasma deposition. In this paper, we report on the crystal structure, electron mobility and some device related properties of these materials. The materials were grown using mixtures of either Germane and methane, with significant hydrogen dilution, or from mixtures of ethylene and germane, also with significant hydrogen dilution. X-ray diffraction measurements indicated a predominantly <111> crystal structure. The grain size was in the range of 10 nm. Raman measurements clearly show the 300 cm-1 Ge peak in the films. Electron Hall mobilities were measured in these films and were found to be in the range of 2.5-3 cm2/V-sec. Proof-of-concept p+nn+ junction devices were fabricated and showed distinct photovoltaic properties. The open circuit voltage was found to be a strong function of the itnerfaces between n+ and n layers, and between p+ and n layers. The use of an amorphous n+/n interface at the back of the improved the device performance significantly. Capacitance measurements indicated that the device behaved according to standard p/n junction theory, with the n- doping in the base layer being in the 1017/cm3 range. Thus, the base layer was not intrinsic, but rather n type, as may be expected for a crystalline as opposed to amorphous material. Quantum efficiency data indicated that as C was added to the material, the edge of the QE curve shifted to higher photon energies, indicating larger bandgaps.
High Temperature n- and p-type Doped Microcrystalline Silicon Layers Grown by VHF PECVD Layer-by-Layer Deposition
Authors: Gordijn A. , Rath J.K. , Schropp R.E.I. 
Published: June 2019

AbstractDue to the high temperatures used for high deposition rate microcrystalline (μc-Si:H) and polycrystalline silicon, there is a need for compact and temperature-stable doped layers. In this study we report on films grown by the layer-by-layer method (LbL) using VHF PECVD. Growth of an amorphous silicon layer is alternated by a hydrogen plasma treatment. In LbL, the surface reactions are separated time-wise from the nucleation in the bulk. We observed that it is possible to incorporate dopant atoms in the layer, without disturbing the nucleation. Even at high substrate temperatures (up to 400°C) doped layers can be made microcrystalline. At these temperatures, in the continuous wave case, crystallinity is hindered, which is generally attributed to the out-diffusion of hydrogen from the surface and the presence of impurities (dopants).We observe that the parameter window for the treatment time for p-layers is smaller compared to n-layers. Moreover we observe that for high temperatures, the nucleation of p-layers is more adversely affected than for n-layers. Thin, doped layers have been structurally, optically and electrically characterized. The best n-layer made at 400°C, with a thickness of only 31 nm, had an activation energy of 0.056 eV and a dark conductivity of 2.7 S/cm, while the best p-layer made at 350°C, with a thickness of 29 nm, had an activation energy of 0.11 V and a dark conductivity of 0.1 S/cm. The suitability of these high temperature n-layers has been demonstrated in an n-i-p microcrystalline silicon solar cell with an unoptimized μc-Si:H i-layer deposited at 250°C and without buffer. The Voc of the cell is 0.48 V and the fill factor is 70 %.
Deposition of Device Quality μc-Si Films and Solar Cells at High Rates by HWCVD in a W Filament Regime where W/Si Formation is Minimal
Authors: Iwaniczko E. , Mahan A.H. , Yan B. , Gedvilas L.N. , Williamson D.L. , Nelson B.P. 
Published: June 2019

Abstractμc-Si has traditionally been deposited by Hot Wire CVD at a low filament temperature. At these temperatures, silicides rapidly form on the filament surface, leading in the case of a tungsten filament to both film reproducibility and filament lifetime issues. By depositing films consecutively using identical deposition parameters, these issues are chronicled for a filament temperature of ∼ 1750°C. Upon increasing the filament temperature to ∼ 1825-1850°C, these reproducibility and lifetime issues disappear and, by lowering both the substrate temperature and chamber pressure, device quality μc-Si is deposited at high deposition rates in a filament regime where tungsten silicide formation is minimal. Both single junction and tandem solar cells are fabricated using this material, confirming the validity of this approach.
Hole Drift-Mobility Measurements in Contemporary Amorphous Silicon
Authors: Dinca S. , Ganguly G. , Lu Z. , Schiff E. A. , Vlahos V. , Wronski C. R. , Yuan Q. 
Published: June 2019

AbstractWe present hole drift-mobility measurements on hydrogenated amorphous silicon from several laboratories. These temperature-dependent measurements show significant variations of the hole mobility for the differing samples. Under standard conditions (displacement/field ratio of 2×10-9 cm2/V), hole mobilities reach values as large as 0.01 cm2/Vs at room-temperature; these values are improved about tenfold over drift-mobilities of materials made a decade or so ago. The improvement is due partly to narrowing of the exponential bandtail of the valence band, but there is presently little other insight into how deposition procedures affect the hole drift-mobility.
Recombination in n-i-p (Substrate) a-Si:H Solar Cells with Silicon Carbide and Protocrystalline p-Layers
Authors: Vlahos V. , Deng J. , Pearce J.M. , Koval R.J. , Ferreira G.M. , Collins R.W. , Wronski C.R. 
Published: June 2019

AbstractA study was carried out on hydrogenated amorphous silicon (a-Si:H) n-i-p (substrate) solar cell structures with p-a-SiC:H and highly diluted p-Si:H layers grown with different dilution ratios R=[H2]/[SiH4]. The contributions of the recombination at the p/i interfaces to the forward bias dark current characteristics were identified and quantified for the different cell structures. In both cell structures the role of the p/i interfaces was identified and it is found that the lowest p/i interface recombination is obtained with protocrystalline p-Si:H layers having no microcrystalline component. The results with p-Si:H layers are attributed not only to their properties but also to the subsurface modification of the intrinsic layer. Evidence is also presented that points to the beneficial effects of the high hydrogen dilution and power used in the deposition of these p-layers in creating the p/i interface regions. The limitations on 1 sun open circuit voltage (VOC) imposed by the p/i recombination present in all the cell structures is consistent with the mechanisms proposed by Deng et al.[1]. The results presented here also point to why the 1 sun VOC in protocrystalline p-Si:H solar cells is higher than that in p-a-SiC:H cells.
Combinatorial Approach to Thin-Film Silicon Materials and Devices
Authors: Wang Qi , Tessler Leandro R. , Moutinho Helio , To Bobby , Perkins John , Han Daxing , Ginley Dave , Branz Howard M. 
Published: June 2019

AbstractWe apply combinatorial approaches to thin-film Si materials and device research. Our hot-wire chemical vapor deposition chamber is fitted with substrate xyz translation, a motorized shutter, and interchangable shadow masks to implement various combinatorial methods. For example, we have explored, in detail, the transition region through which thin Si changes from amorphous to microcrystalline silicon. This transition is very sensitive to deposition parameters such as hydrogen-to-silane dilution of the source gas, chamber pressure, and substrate temperature. A material library, on just a few substrates, led to a three-dimensional map of the transition as it occurs in our deposition system. This map guides our scientific studies and enables us to use several distinct transition materials in our solar-cell optimization research. We also grew thickness-graded wedge samples spanning the amorphous-to-microcrystalline Si transition. These single stripes map the temporal change of the thin silicon phase onto a single spatial dimension. Therefore, the structural, optical, and electrical properties can easily be studied through the phase transition. We have examined the nature of the phase change on the wedges with Raman spectroscopy, atomic force microscopy, extended x-ray absorption fine structure (EXAFS), x-ray absorption near-edge spectroscopy (XANES), ultraviolet reflectivity, and other techniques. Combinatorial techniques also accelerate our device research. In solar cells, for example, the combinatorial approach has significantly accelerated the optimization process of p-, i-, n-, and buffer layers through wide exploration of the complex space of growth parameters and layer thicknesses. Again, only a few deposition runs are needed. It has also been useful to correlate the materials properties of single layers in a device to their performance in the device. We achieve this by depositing layers that extend beyond the device dimensions to permit independent characterization of the layers. Not only has the combinatorial approach greatly increased the rate of materials and device experimentation in our laboratory, it has also been a powerful tool leading to a better understanding of structure-property relationships in thin-film Si.
A Study of Atomic Layer Deposition and Reactive Plasma Compatibilitywith Mesoporous Organosilicate Glass Films
Authors: Ryan E. Todd , Freeman Melissa , Svedberg Lynne , Lee J.J. , Guenther Todd , Connor Jim , Yu Katie , Sun Jianing , Gidley David W. 
Published: June 2019

AbstractThe compatibility of ALD and CVD metal deposition with mesoporous and microporous carbon-doped organosilicate glass (OSG) films was examined. Blanket film studies using TEM, TOF-SIMS, and positron lifetime spectroscopy demonstrate that ALD Wand TaN penetrate deep into the mesoporous film via the film's connected pore structure. In contrast, metal penetration into microporous OSG films was not observed. He and NH3 plasma pretreatments to the mesoporous OSG film surface did not seal the mesopores to ALD metal penetration, but the plasmas did damage the bulk of the mesoporous OSG film with varying severity. The results indicate that porosity, pore size, and/or pore structure regulate ALD/CVD precursor diffusion and that ALD metal deposition is a good probe of pore sealing strategies.
Adhesion Enhancement for Multiple Level Cu/SiLKTM Integration
Authors: Chen X. T. , Lu D. , Tan Y. T. , Chen Y. W. , Foo P. D. 
Published: June 2019

AbstractThe effects of various integration processes on the adhesion of SiLKTM to the Ta barrier layer were studied. We have found that the H2/He reactive plasma clean treatment (RPC) causes poor adhesion between these two layers. The results obtained from TOF-SIMS showed that hydrogen plasma had caused damage to the SiLK surface causing molecular fragmentation. Hydrogen had also been chemically incorporated into SiLK to form a hydrogen-saturated surface. To improve adhesion, an argon sputtering process was employed to remove this altered SiLK surface layer. Adhesion was found to have been improved and no delamination was observed even up to integration of 7 metal layers.
Quantitative Measurements of Subcritical Debonding of Cu Films from Glass Substrates
Authors: Pang M. , Baker S.P. 
Published: June 2019

AbstractSubcritical debonding of Cu films from silicate glass substrates has been studied using a driver film method. In this method, a highly stressed Cr overlayer is imposed to debond the target Cu film from the substrate. Substrates included a commercial flat panel display glass and glasses having composition (2SiO2)x(CaO·Al2O3)1-x. A range of strain energy densities for driving interfacial crack growth was provided by depositing Cr driver layers with varying thickness. The film debond velocity was obtained experimentally. The stresses in Cu and Cr were measured and used to obtain the strain energy release rate. The effect of oxygen concentration and substrate composition on subcritical debonding was studied. A kinetic crack model previously developed for bulk ceramics was modified and applied. Differences in adhesion could be attributed to differences in density of strong Cu-O bonds across the interface.
Deposition and Characteristics of Tantalum Nitride films by Plasma Assisted Atomic Layer Deposition as Cu Diffusion Barrier
Authors: Na Kyoung-Il , Park Se-Jong , Jeong Woo-Cheol , Kim Se-Hoon , Boo Sung-Eun , Bae Nam-Jin , Lee Jung-Hee 
Published: June 2019

AbstractFor a diffusion barrier against Cu, tantalum nitride (TaN) films have been successfully deposited by both conventional thermal atomic layer deposition (ALD) and plasma assisted atomic layer deposition (PAALD), using pentakis (ethylmethlyamino) tantalum (PEMAT) and ammonia (NH3) as precursors. The growth rate of PAALD TaN at substrate temperature 250° was slightly higher than that of ALD TaN (0.80 Å/cycle for PAALD and 0.75 Å/cycle for ALD). Density of TaN films deposited by PAALD was as high as 11.0 g/cm3, considerably higher compared to the value of 8.3 g/cm3 obtained by ALD. The N: Ta ratio for ALD TaN was 44: 37 in composition and the film contained approximately 8∼10 atomic % carbon and 11 atomic % oxygen impurities. On the other hand, the ratio for PAALD TaN layers was 47: 44 and the respective carbon and oxygen contents of TaN layers decreased to 3 atomic % and 4 atomic %. The stability of 10 nm-thick TaN films as a Cu diffusion barrier was tested through thermal annealing for 30 minutes in N2 ambient and characterized by XRD, which proves the PAALD deposited TaN film to maintain better barrier properties against Cu below 800°.
Vapor Treatment of Copper Surface Using Organic Acids
Authors: Ishikawa Kenji , Yagishita Teruo , Nakamura Moritaka 
Published: June 2019

AbstractThe mechanism for cleaning Cu surfaces using the vapor from organic acids was studied by infrared reflection-absorption spectroscopy (IR-RAS) and by analysis of products collected using a cold-trap placed downstream of a reactor. When formic acid vapor was exposed to oxidized Cu samples heated to about 200°C for about a half an hour, the oxides were reduced. The surface seemed to have a shiny metallic appearance but no Cu-containing volatile products were collected, and the decomposition of formic acid molecules into CO2 was observed. In contrast, using acetic acid vapor, Cu-containing etching products were collected and identified as a dinuclear Cu (II) acetate complex. The vapor treatment using formic and acetic acids can be reduced Cu oxides to have metallic Cu surfaces. Furthermore, controlling temperature and choice of organic acids enabled the advantageous establishment of a control for the reduction in, and etching of, the Cu oxides.
Impact of Annealing on the Resistivity of Ultrafine Cu Damascene Interconnects
Authors: Steinlesberger G. , Engelhardt M. , Schindler G. , Steinhögl W. , Traving M. , Hönlein W. , Bertagnolli E. 
Published: June 2019

AbstractThe influence of different annealing conditions on the electrical resistivity of copper damascene interconnects with lateral dimensions down to sub-50 nm was studied. Different thermal treatments after copper plating as well as annealing processes in addition to the final anneal step were carried out in order to study the microstructural change of copper damascene lines. It was found that rapid thermal annealing (RTA) at high temperatures (600°C) leads to an enlargement of the Cu grains by a factor of 2 for wide lines, whereas a significant impact of annealing on the median grain size of ultrafine lines was not observed. This is attributed to the geometrical limitation of the grain growth process. As a result, the size effect in Cu nano-interconnects which is mainly determined by grain boundaries acting as scattering sites for electrons cannot be reduced significantly by using thermal treatments.
A Novel Technique to Re-construct 3D Void in Passivated Metal Interconnects
Authors: Tan Cher Ming , Gan Zhenghao , Zhang Guan , Prasad Krishnamachar , Zhang Dao Hua 
Published: June 2019

AbstractIn the present work, a novel method is proposed to re-construct voids in passivated metal interconnections. In this method, the conventional SEM and EBIC systems are assembled and utilized without much modification. In principle, a constant current is applied to the metal interconnections while an electron beam is scanning and impinging upon the surface of the sample. The voltage at the terminals is monitored simultaneously during electron beam scanning. Resistance change, and hence voltage perturbation are expected when the electron beam approaches the defective area, caused by uneven electron beam heating (EBH) and heat transmission. Information on defects or voids is thus obtained by analyzing the voltage alteration. Finite element simulation showed that the recorded voltage perturbation is not dependent of the length of the interconnect, but a linear function of the void volume. Thus, the method is essentially useful as the metal length has increased tremendously in copper technology. In addition, it can provide the void size and depth, with the possibility to reconstruct the entire void shape in 3D.
AlCu Pattern Generation on 3D StructuredWafer Using Multi Level Exposure Method on Electrodeposited Polymer Material
Authors: Sharma Vineet , Suriadi Arief B. , Berauer Frank , Mittelstadt Laurie S. 
Published: June 2019

AbstractNormal photolithography tools have focal depth limitations and are unable to meet the expectations of high resolution photolithography on highly topographic structures. This paper shows a cost effective and promising technique of combining two different approaches to achieve critical dimensions of traces on slope pattern continuity on highly topographic structures. Electrophoretically deposited photoresist is used on 3-D structured wafers. This photoresist coating technique is fairly known in the MEMS industries to achieve uniform and conformal photoresist films on 3D surfaces. Multi step exposures are used to expose electrophoretically deposited photoresist. AlCu (Cu-0.5%), 0.47-0.53 μm thick metal film is deposited on 3D structured silicon substrate to plate photoresist. By combining these two novel methods, metal (AlCu) traces of 75 μm line width and 150 μm pitch (from top flat to down the slope) have been demonstrated on isotropically etched 350 μm deep trenches with 5-10% line width loss.