bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) A Rational Design for Batteries at Nanoscale by Atomic Layer Deposition
Authors: Liu Chanyuan , Gillette Eleanor , Chen Xinyi , Pearse Alexander J , Kozen Alexander C , Schroeder Marshall A , Gregorczyk Keith , Lee Sang Bok , Rubloff Gary W
Published: October 2015

A self-aligned nanostructured battery fully confined within a single nanopore presents a powerful platform to determine the rate performance and cyclability limits of nanostructured storage devices. Atomic layer deposition (ALD) has enabled us to create and evaluate such structures, comprised of nanotubular electrodes and electrolyte confined within anodic aluminum oxide (AAO) nanopores. This nanopore battery displays exceptional power-energy performance and cyclability when tested as a massively parallel device (~2billion/cm2), each with ~1mm3 volume (~1fL). (1) Cycled between 0.2V and 1.8V, this full cell has capacity retention of 95% at 5C rate and 46% at 150C, with more than 1000 charge/discharge cycles. Further increase of full cell output potential is also demonstrated. These results demonstrate the promise of ultrasmall, self-aligned/regular, densely packed nanobattery structures as a testbed to study ionics and electrodics at the nanoscale with various geometrical modifications and as a building block for high performance energy storage systems.
Spatial Atmospheric ALD of Functional Layers for CIGS Solar Cells
Authors: Illiberi A. , Frijters Corne , Balder Ellis , Poodt Paul , Roozeboom Fred
Published: October 2015

Spatial Atmospheric Atomic Layer Deposition combines the advantages of temporal ALD, i.e. excellent control of film composition and uniformity over large area substrates, with high growth rates (up to nm/s). In this paper we present a short overview of our research activity carried out on S-ALD of functional thin films for the front window of copper indium gallium di-selenide (CIGS) solar cells. Zn(O,S) and ZnO:Al are grown by co-injecting the vaporized precursors of the cationic (O, S) and anionic (Zn, Al) elements, respectively. An insight on the growth characteristics and properties of Zn(O,S) and ZnO:Al is presented.
(Invited) Atomic Layer Deposition of Nanophase Materials for Electrical Energy Storage
Authors: Meng Xiangbo , Elam Jeffrey W
Published: October 2015

Batteries as electrical energy storage (EES) devices hold great promise to accelerate the implementation of renewable clean energies such as wind and solar power. More broadly, EES have a major impact on three domains: portable electronics, transportation, and stationary storage in smart grids. Despite their dominance in portable electronics, batteries are still not sufficient in energy density, and are too expensive for wide-scale deployment in transportation and smart grids. In this context, current research efforts are pursuing cost-effective and high-energy batteries as next-generation EES devices. Recently, atomic layer deposition (ALD) has emerged as a new thrust for these goals and enabled to provide multiple technical solutions with high flexibility. Benefited from its unique mechanism, ALD in the first place demonstrated exceptional capabilities in developing atomic-precisely controlled nanostructures for battery electrodes (anodes and cathodes) with improved performance. In addition, ALD exclusively enables accurate sub-nano to nanoscale conformal films to finely tailor battery interfaces between electrodes and electrolytes for improved stability and safety. This article summarized some of the recent advances in ALD technology for batteries.
Sensitization of ZnO by Light-Harvesting Antennas Composed of Multiple Stacked Dyes Grown by Liquid-Phase Molecular Layer Deposition
Authors: Matsumura Yusaku , Yoshimura Tetsuzo
Published: October 2015

We propose sensitization of ZnO by multi-dye stacked light-harvesting antennas grown by liquid-phase molecular layer deposition (LP-MLD), which grows organic tailored materials with designated molecular arrangements by sequentially exposing substrate surfaces to different kinds of source molecules in liquid phase. Using rose bengal (RB) and eosine (EO) for the p-type dyes, and crystal violet (CV) and brilliant green (BG) for the n-type dyes, three-dye stacked light-harvesting antennas were grown on ZnO. [ZnO/EO/CV/RB] structure exhibited a wide photocurrent spectrum, which is a superposition of the photocurrent spectra of EO, CV, and RB, rising up around 450 nm to extend over 600 nm in wavelength. In [ZnO/EO/BG/RB] structure the photocurrent generated by EO was drastically reduced. This can be attributed to the electron transfer from EO to BG, which is suggested by the energy-level schemes determined using the photoemission yield spectroscopy in air.
Room Temperate Bonding of Al2O3 Layers by Atomic Layer Deposition on Polyimide Substrates
Authors: Matsumae Takashi , Dushatinski Thomas , Abdel-Fattah Tarek M , Suga Tadatomo , Zhang Kai , Chen Xin , Baumgart Helmut
Published: October 2015

Room temperature bonding of Al2O3 layers deposited by Atomic Layer Deposition (ALD) was studied for gas diffusion barrier structures on polymer films. A modified method of the surface activated bonding (SAB) was applied for the bonding of ALD Al2O3 coated polyimide sheets. ALD deposition was performed at different process temperatures of 80, 150 and 250 ºC. The results of AFM surface profile demonstrate that samples prepared at a higher temperature in ALD process exhibit a rougher surface. Also, polymer films processed at high temperature suffer larger warpage. The size of the bonded area was optimized when the ALD synthesis of Al2O3 was performed at 80ºC, leaving only a small, unbonded area.
Atomic Layer Deposition and in-Situ Characterization of Yttrium Oxide and Yttria-Stabilized Zirconia
Authors: Lecordier Laurent
Published: October 2015

Y2O3 and YSZ thin films were thermally deposited by atomic layer deposition in a commercial ALD cross flow reactor. Using a Low Vapor Pressure Delivery system, tris(ethylcyclopentadienyl) yttrium - Y(EtCp)3 - heated at 120˚C - was used as a precursor. Tetrakis(dimethylamido)zirconium - TDMAZr and water were used for ZrO2. In-situ quartz crystal microbalance and spectroscopic ellipsometry were implemented in order to rapidly screen the ALD process space from 150 to 300˚C as a function of Y(EtCp)3 and H2O doses and purge conditions. The optimized process led to excellent wafer-scale performances with good thickness uniformity and excellent process reproducibility. The yttria film properties were optimal around 225-250˚C with a high refractive index (1.93), low carbon concentration (<0.1%) and Y0.4O0.6 stoichiometry. The growth of ternary YSZ oxides was monitored by QCM and showed that the composition of yttria in zirconia was readily controlled by adjusting the Y2O3 to ZrO2 cycle ratio.
Improving Graphene Conductivity through Selective Atomic Layer Deposition
Authors: Liu Chanyuan , Han Xiaogang , Bao Wenzhong , Pearse Alexander J , Hu Liangbing , Rubloff Gary W
Published: October 2015

We present a method to electrically heal and connect graphene flakes via selective atomic layer deposition (ALD) of conductive materials. Selective growth of conductive materials is observed on graphene cracks and edges but exhibits a significant nucleation barrier on intact basal planes due to the chemical inertness. Self-assembled graphene flake films have 10X conductivity after selective platinum (Pt) ALD. In addition, a graphene field effect transistor (FET) model system is used to monitor graphene carrier density and mobility variation after ALD growth. Selective ALD of other conductive materials is also discussed.
(Invited) Vacuum Ultraviolet Photochemical Atomic Layer Deposition of Alumina and Titania Films
Authors: Chalker Paul Raymond , Marshall Paul A , Dawson Karl , Sutcliffe Christopher J , Brunell Ian F , Sedghi Naser , Hall Stephen , Potter Richard J
Published: October 2015

Conventional atomic layer deposition (ALD) is a thermo-chemical process where co-reagents are sequentially pulsed in cycles onto a heated substrate. As an alternative to substrate heating, various forms of other “non-thermal” ALD processes are being investigated. Herein, the photochemical atomic layer deposition of Al2O3 and TiO2 thin films at 60°C is reported using a shuttered vacuum ultraviolet light source to excite molecular oxygen as a co-reagent with the metal precursors. The growth mechanisms using trimethyl aluminium and titanium tetraisopropoxide precursors, are investigated using in-situ quartz crystal microbalance and post-deposition ellipsometric measurements. The photochemical ALD Al2O3 films exhibit different capacitance equivalent thicknesses for irradiated and masked regions respectively, even after post-deposition annealing. The photochemical ALD titania films are amorphous and when incorporated into Pt / TiO2 / Pt metal - insulator - metal structures, the titania exhibits a resistive switching behavior.
New Insights into Sequential Infiltration Synthesis
Authors: Elam Jeffrey W , Biswas Mahua , Darling Seth , Yanguas-Gil Angel , Emery Jonathan D. , Martinson Alex B. F. , Nealey Paul F. , Segal-Peretz Tamar , Peng Qing , Winterstein Jonathan , Liddle J. Alexander , Tseng Yu-Chih
Published: October 2015

Sequential infiltration synthesis (SIS) is a process derived from ALD in which a polymer is infused with inorganic material using sequential, self-limiting exposures to gaseous precursors. SIS can be used in lithography to harden polymer resists rendering them more robust towards subsequent etching, and this permits deeper and higher-resolution patterning of substrates such as silicon. Herein we describe recent investigations of a model system: Al2O3 SIS using trimethyl aluminum (TMA) and H2O within the diblock copolymer, poly(styrene-block-methyl methacrylate) (PS-b-PMMA). Combining in-situ Fourier transform infrared absorption spectroscopy, quartz-crystal microbalance, and synchrotron grazing incidence small angle X-ray scattering with high resolution scanning transmission electron microscope tomography, we elucidate important details of the SIS process: 1) TMA adsorption in PMMA occurs through a weakly-bound intermediate; 2) the SIS kinetics are diffusion-limited, with desorption 10x slower than adsorption; 3) dynamic structural changes occur during the individual precursor exposures. These findings have important implications for applications such as SIS lithography.
Atomic Layer Deposition of Ultrathin TaN and Ternary Ta1-XAlXNy Films for Cu Diffusion Barrier Applications in Advanced Interconnects
Authors: Consiglio Steven , Yu Kyle , Dey Sonal , Tapily Kandabara , Clark Robert D. , Hasegawa Toshio , Wajda Cory S. , Leusink Gert J. , Diebold Alain C.
Published: October 2015

Ultrathin TaN and Ta1-xAlxNy films were deposited by ALD using metallorganic precursors and were evaluated for their effectiveness in Cu diffusion barrier applications compared to a PVD TaN control. Ta1-xAlxNy films with x = 0.21-0.88 were deposited by varying Ta:Al cycle ratios. The effectiveness of the barrier layers against Cu diffusion was investigated using in-situ-ramp-anneal-synchrotron-XRD on stacks with 1.8 nm layers between 50 nm PVD Cu and Si. The kinetics of Cu3Si formation was assessed by performing a Kissinger-like analysis to determine the effective activation energy (Ea) for Cu silicidation. Compared to the stack with a PVD TaN barrier, the stacks with the ALD films exhibited a higher crystallization temperature for Cu silicidation. Based on the estimated Ea values, grain boundary and lattice diffusion of Cu were identified as the dominant failure mechanisms for the ALD and PVD films, respectively. For 3 nm films, GIIXRD showed evidence of nanocrystallites embedded in an amorphous matrix with broad peaks corresponding to cubic phase for the ALD films and hexagonal phase for the PVD film. The superior performance of the ALD barriers has been attributed to the formation of a higher density cubic phase in the ALD films as compared to the lower density hexagonal phase in the PVD film. The study further elucidates the difference in initial failure mechanisms due to differences in barrier crystallinity and associated phase. Additionally, incorporation of Al in ALD Ta1-xAlxNy (x=0.33) seems to aid the formation of a barrier film which is closer to amorphous than the case of ALD TaN.
Proposal of Integrated Sensitized Solar Cell Films Based on Sputtered ZnO Thin Films
Authors: Jassim Alshaalah , Takizawa Satoshi , Yoshino Chie , Yoshimura Tetsuzo
Published: October 2015

One of the issues in dye-sensitized solar cells (DSCs) is the internal resistivity. To solve this, we proposed the waveguide-type sensitized solar cell based on thin-film semiconductors, where, tapered vertical waveguides and planar waveguides collect light beams and guide them to the solar cells. In the present work, fabrication and evaluation of the tapered vertical waveguide films, and sensitization of ZnO thin films are investigated. The tapered vertical waveguides are fabricated by the built-in mask method using a photopolymer exposed to tilted ultra-violet beams to form beveled walls after development. The tapered vertical waveguide with a taper angle of 30o is found to increase the light beam collecting efficiency by 2~3 time. For sensitization of ZnO thin films, we attempt to apply the sputtering for ZnO thin film growth, and two-dye stacked structures of p-type dye/n-type dye or ZnO/Cr2O3 multi-layer structures for sensitization.
Spectroscopic Ellipsometry Characterization of Pd Thin Film Grown by Atomic Layer Deposition
Authors: Zhang Yihang , Zhou Xueqi , Cao Kun , Chen Xiuguo , Liu Shiyuan , Shan Bin , Chen Rong
Published: October 2015

Pd thin films grown by atomic layer deposition have been studied through spectroscopic ellipsometer with Bruggeman effective medium approximation (B-EMA) model to evaluate the optical properties, thickness and Pd coverage of the films. For the fitting results of thickness, mean square error increases with the gain of ALD cycles. At smaller Pd ALD cycles less than 400, the better fitting results of Pd coverage were obtained compared with Maxwell-Garnett effective medium approximation. It verifies the B-EMA is better for fitting samples with smaller filling fractions. Our study can be extended to characterize other thin films.
Sensitization of ZnO in Stacked Structures Containing Multiple Dyes Grown Using Liquid Phase Molecular Layer Deposition
Authors: Liu TingTing , Matsumura Yusaku , Yoshimura Tetsuzo
Published: October 2015

Sensitization by two-dye-stacked structures of p-type dye/n-type dye adsorbed on ZnO can be applied to dye-sensitized solar cells. We attempted sensitization by stacked structures containing three or four kinds of dyes for further spectral widening. The structures were fabricated by liquid-phase molecular layer deposition (LP-MLD) using the electrostatic force between p-type dyes accepting electrons (rose bengal (RB), eosine (EO)) and n-type dyes donating electrons (crystal violet (CV), brilliant green (BG)). After p-type dyes of p1 and p2 were deposited on ZnO, n-type dyes of n1 and n2 were deposited to connect them to p1 or p2. [ZnO/EO/CV+BG] exhibited a broad photocurrent spectrum extending to the long wavelength region beyond 600 nm. In [ZnO/RB+EO/CV+BG], although a strong sensitization was observed in the long wavelength region, the photocurrent decreased in the short wavelength region. These results will be explained by the energy-level schemes determined using the photoemission yield spectroscopy in air.
Selective Removal of Native SiO2 Using XeF2
Authors: Hinckley Adam , Mancheno-Posso Pablo , Lai C. Steven , Muscat Anthony J.
Published: October 2015

The selective removal of native SiO2 with respect to Si and thermal SiO2 using XeF2 was studied with ellipsometry, temperature-programmed desorption (TPD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (XPS). The native SiO2 layer was removed with a static process at a pressure of 1 Torr and room temperature, but the Si substrate was roughened on a micron scale. To avoid roughening, a continuous flow of XeF2 was used at pressures lower than 10 mTorr. XPS analysis confirmed that the XeF2 exposure fluorinated the native oxide and both the oxide and fluorine were removed by heating to 925 K (650 °C). AFM showed no change in surface roughness after the low pressure exposure and heating, and together with XPS peak area ratios before and after XeF2 show that the native oxide was etched without etching the underlying Si substrate.
A Spatial ALD Oxide Passivation Module in an All-Spatial Etch-Passivation Cluster Concept
Authors: Roozeboom Fred , van den Bruele Fieke , Creyghton Yves , Poodt Paul , Kessels W.M.M.
Published: October 2015

Traditional plasma etching in silicon is often based on the so-called ‘Bosch’ etch with alternating half-cycles of a directional Si-etch and a fluorocarbon polymer passivation, respectively. Also shallow feature etching is often performed as a cycled process. Similarly, ALD is cyclic with the additional benefit of being composed of half-reactions that are self-limiting, thus enabling a layer-by-layer growth mode. To accelerate growth rate, spatial ALD has been commercialized as a large-scale, high-throughput, atmospheric-pressure method. In this paper we describe a related concept for high-rate spatially-divided etching which eventually may be further developed towards Atomic Layer Etching. The process is converted from the time-separated into the spatially-separated regime by inserting N2-gas ‘curtains’ confining the reactive gases to individual injection slots in a gas injector head, and also serving as gas-bearing. By moving substrates back and forth under such gas injector one can perform alternate etching/passivation-deposition cycles at optimized local pressures, thus eliminating the idle times for switching pressure or purging. An extra improvement towards an all-spatial approach is the use of ALD-based oxide (Al2O3, SiO2, etc.) as passivation during, or as gap-fill after etching. This disruptive concept, named spatial ALD-enabled RIE, has industrial potential for cost-effective front-end-of-line and back-end-of-line processing, especially in patterning structures requiring minimum interface, line edge and fin sidewall roughness (atomic-scale fidelity with selective removal of atoms and retention of sharp corners). Besides in CMOS scaling this etch concept may also become an interesting option for fast die dicing of silicon (or III/V) in TSV and MEMS processing.
(Invited) Divide Et Impera: Towards New Frontiers with Atomic Layer Etching
Authors: Lill Thorsten , Kanarik Keren J. , Tan Samantha S.H. , Shen Meihua , Pan Yang , Marks Jeffrey , Vahedi Vahid , Gottscho Richard A.
Published: October 2015

Atomic layer etching (ALE) is emerging as a solution for advanced etch applications which require atomic scale fidelity /1/. In analogy to Atomic Layer Deposition (ALD), ALE is separated into two individual steps, one for surface modification and one for removal /2,3,4/. Similar to Reactive Ion Etching (RIE), the fundamental mechanism of ALE is based on ion-neutral synergism. Because of the time separation of the surface modification by neutrals and the removal step by ions, this synergism manifests itself in the saturation of the removal step. The modification step is saturated which means that the fundamental etch mechanism of directional ALE is chemically enhanced sputtering /5-8/. The window for directional ALE is given by the sputter threshold of the bulk material on the high end and the sputter threshold of the modified layer on the low end.
(Invited) Understanding and Controlling Electrochemical Effects in Wet Processing
Authors: Raghavan Srini , Chiang Chieh-Chun
Published: October 2015

Electrochemical techniques have long been used in understanding and improving the performance of various wet chemical processing steps such as etching, cleaning, passivation and rinsing used in integrated circuit (IC) manufacturing. The objective of this paper is to provide a few examples of how electrochemical techniques can be used to probe some important areas in wet processing. It is not intended to be an exhaustive review of techniques and problems reported in the literature.
Effects of Diluted-NH4OH as Conductive Rinse Water in Single Wafer Cleaning Processes
Authors: Hayashi Yoshifumi , Kawakami Masayuki , Yano Daisaku , Yamanaka Koji
Published: October 2015

We propose diluted-NH4OH to use as a rinse water combined with or instead of CO2-dissolved water (CO2 water) for preventing electrostatic charge in wet cleaning of semiconductor manufacturing processes. We have developed a novel diluted-NH4OH generator featuring a tube injection which enables precise dilution of concentrated NH4OH reagent directly, and confirmed the effect of preventing electrostatic charge on wafer surfaces by diluted-NH4OH. And we have also evaluated the inhibition of copper corrosion on Si wafer by diluted-NH4OH in comparison with CO2 water and deionized water (DI water), and found that diluted-NH4OH is the best rinse water among these three, by which the static charge is prevented and also the corrosion of copper is inhibited especially when the concentration of NH3 in diluted-NH4OH is controlled to be precisely to have the conductivity range of 10 to 20 μS/cm.
Sulfate Adsorption onto and Desorption from Silicon Dioxide Films
Authors: Wu Bing , Raghavan Srini
Published: October 2015

Sulfate ion adsorption onto and desorption from silicon dioxide surface has been investigated using a quartz crystal microbalance with dissipation monitoring (QCM-D) capability. A viscoelastic model was used to calculate adsorption/desorption amount. The sulfate ion uptake at pH 6.8 varied linearly with sulfate concentration in the range 0.01 M to 0.6 M. Based on the hydrated radius of sulfate ion, the adsorption (uptake) amount indicated multilayer adsorption. The first order rate constant for sulfate desorption with DI water is approximately 0.04 s-1 and 0.12s-1 for flow rates of 0.2 ml/min and 1.0 ml/min, respectively.
(Invited) Metallic Contamination Control in Advanced ULSI Processing
Authors: Saga Koichiro
Published: October 2015

We have extensively reviewed metallic contamination control including the analysis, prevention, removal, and gettering in advanced ULSI manufacturing. Detection and removal of metallic contamination on the III-V surfaces used for high mobility channels in logic devices will be big challenges. Better understanding the behavior and the electric activities of metal impurities diffusing and the gettering design based on the physical properties of metals is required for controlling yield of memory devices, image sensors and high voltage MOS transistors.
Contamination Specifications, an Overall Perspective
Authors: Mertens Paul W
Published: October 2015

Specifications for residual contamination have played a determining role in the development of cleaning processes. Typically different categories of contamination are discriminated: such as particle-type of contaminants and contaminants that are more dispersed over the surface. The intention of this study is to reflect on front side contamination specifications particularly in view of further feature down scaling. The different specification values for particles and dispersed contaminants are compared to each other. It turns out that in terms of total amount (volume) of contamination particle specifications are far more stringent than specification values for dispersed contamination such as C or metals. Finally a new type of specification is proposed that can take over from the current set of specification values.
(Invited) Supercritical Drying: A Sustainable Solution to Pattern Collapse of High-Aspect-Ratio and Low-Mechanical-Strength Device Structures
Authors: Chen Han-Wen , Verhaverbeke Steven , Gouk Roman , Leschkies Kurtis , Sun Shiyu , Bekiaris Nikos , Visser Robert J.
Published: October 2015

Collapse of nanostructures with high aspect ratio and/or low mechanical strength during drying step in wet process has become a critical issue in semiconductor industry. Even current workable drying practices are facing steeply rising challenges from rapid device scaling advancements. The objective of this work, following evaluation of multiple advanced drying technique, is to develop a sustainable non-stiction drying solution incorporating supercritical fluids. Leaning-free performance has been consistently demonstrated with our supercritical drying sequence on 2x NAND STI (trench aspect ratio ~20) and low-k trench structures, where pattern collapses were observed under conventional solvent-assisted drying or even with advanced self-assembled monolayer approach. Release of sporadic stiction and complete recovery from global pattern leaning were both achieved with our integrated supercritical drying process. Particle performance < 50 adders @0.09μm in average was attained with background particles subtracted. Metallic contamination analysis with TXRF showed all metal components interested were below detection limit.
Dewetting Model Study on a Spinning Substrate - Challenges for Low Chemical Consumption
Authors: Sano Ken-ichi , Mui David , Kawaguchi Mark
Published: October 2015

A model is proposed to describe the wetting and dewetting dynamics on a spinning wafer with a non-wetting surface. The model is based on the dynamic balance between the wetting and dewetting velocities. The proposed model predicts a theoretical lower limit for the media flow rate to completely wet a wafer surface as a function of the contact angle and wafer rotational speed. The model predictions are found to agree reasonably well with experimental results. The model is also used to develop a low flow process for the removal of titanium nitride. A 66% flow rate reduction is achieved in comparison with the baseline process.
Etching of Silicon Nitride in 3D NAND Structures
Authors: Bassett Derek , Printz Wallace , Furukawa Takahiro
Published: October 2015

We present results of experimental measurements, simulations, and models to better understand etching of SiN with H3PO4 in 3D NAND structures. SiN and SiO2 etch rates were measured on blanket wafers, and those etch rates were used to simulate etching of 3D NAND structures. Results show that the etching is reaction limited, and that diffusion and acid flow rate has no effect on the local etch rate, but temperature and concentration do affect the etch rate.
Selective Silicon Nitride Etch with Hot Diluted HF– an Alternative to Orthophosphoric Acid
Authors: Garnier Philippe , Neyens Marc , Massin Thomas , Thomassin David , Maurice Carole
Published: October 2015

Orthophosphoric acid is the worldwide standard chemical to quickly and selectively etch thick silicon nitride films towards silicon oxide. Along the semiconductors node evolution, new demands have arisen to etch few nanometers thick SiN films, with much better defectivity than H3PO4. Several alternatives have been developed during the past few years. Among them, a hot very diluted HF process was developed in the early 2000’s. This paper deals with several applications where significant benefits are demonstrated compared with H3PO4: first a Stress Proximity Technic successfully adopted into production mode, secondly a SiN films patterning thanks to a softmask. Although this process benefits from high selectivity, low cost of ownership, good defectivity, its within wafer uniformity still remains poor due to the actual hardware.
Acoustic Characterization of Patterning Degradation during Wet Etching
Authors: Virgilio Christophe , Garnier Philippe , Foucaud Mathieu , Devos Arnaud , Pinceau David , Carlier Julien , Campistron Pierre , Nongaillard Bertrand , Neyens Marc , Broussous Lucile
Published: October 2015

Photoresist degradation can occur during wet etching processes due to chemicals diffusion through the polymer. The adhesion of the resist is not guaranteed anymore and damage on the resist / material interface appears. This phenomenon is usually monitored by optical methods. However, invisible resist degradation cannot be detected and the physical nature of the resist / material modification remains unknown. A high-frequency acoustic echography method has been developed to overcome these problems and has been performed to study the apparition of blisters in a deep UV photoresist exposed to a Standard Clean 1 solution. This technique allows the quantitative detection of resist degradation even if blisters cannot be seen in the resist. It has also been found that gas pockets appear during blisters formation.
(Invited) Reaction Mechanisms on Binary III-V Semiconductor Surfaces during Etching, Passivation, and Deposition
Authors: Muscat Anthony J.
Published: October 2015

Etching of the natives oxides of the III-V semiconductor InGaAs using aqueous and gas phase HF were compared using x-ray photoelectron spectroscopy, ellipsometry, and atomic force microscopy. The mechanisms in both phases are driven by bond polarity. This explains why the surface is terminated by the group V atom, in this case arsenic. The solubility of the fluorides of the substrate atoms in water removes the reaction products. The fluorides of Ga were not volatile at room temperature and remain on the surface after gas phase etching. Annealing to 170 °C desorbed these fluorides. Atomic layer deposition of Al2O3 converted the oxides left on the surface and etched the fluorides. The interface was indium rich after aqueous phase HF etching but near stoichiometric after gas phase HF etching.
Surface Chemistry of III-V Semiconductors After Wet Etching with HCl and H2O2
Authors: Mancheno-Posso Pablo , Muscat Anthony J.
Published: October 2015

GaAs(100) was immersed in water and aqueous mixtures of isopropyl alcohol, ethylene glycol, acetic acid, glycolic acid, tartaric acid, and HCl with and without the addition of H2O2 to understand the etching mechanism. The surface composition after etching was characterized using x-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). Ga and As oxides with high oxidation states dissolve in water, but acids are needed to remove the oxides with low oxidation states. H2O2 oxidized the bulk substrate, and only the acids that have pKa values lower than 4 supported etching. After etching with HCl, the surface is terminated by arsenic chloride (As-Cl).
Chemical Treatments for Native Oxides Removal of GaAs Wafers
Authors: Rebaud Mickaël , Roure Marie-Christine , Loup Virginie , Rodriguez Philippe , Martinez Eugénie , Besson Pascal
Published: October 2015

Two months air-aged GaAs wafers were treated with different chemistries. The effect on oxide removal and surface morphology was studied by XPS and AFM. In order to propose a global sequence to put value-back into these old wafers, a rinsing step with different content of dissolved O2 was practiced after selected chemical treatments. Results show that all applied treatments (HCl, HF, NH4OH and (NH4)2S) are efficient for removing the native oxide. The chemical composition of the obtained surfaces depend of the chemistry. Basic treatments are preferable to conserve a smooth surface. Without S-passivation, a significant oxide growth is observed even if surfaces were only exposed 30 minutes to air. Short descriptions of potential mechanisms occurring at surface are discussed.
Cleaning of InGaAs and InP Layers for Nanoelectronics and Photonics Contact Technology Applications
Authors: Rodriguez Philippe , Toselli Laura , Ghegin Elodie , Rebaud Mickaël , Rochat Névine , Chevalier Nicolas , Martinez Eugénie , Nemouchi Fabrice
Published: October 2015

InGaAs and InP layers were treated by using Ar and He direct plasmas coupled with wet chemical treatments. InP surfaces are more sensitive to the various treatments than the InGaAs ones. Suitable and efficient treatments have been proposed to offer a good compromise between impact on surface and native oxide removal. We have demonstrated that concentrated HCl solution cleanings followed by He direct plasma treatment are efficient for the removal of InGaAs native oxides whereas He plasma exposure combined to a diluted HCl solution cleaning is more suitable for InP surfaces.
Wet Processing for Post-epi & Pre-furnace Cleans in Silicon Carbide Power MOSFET Fabrication
Authors: McMahon J. Jay , Jahanbani Mo , Arthur Stephen , Lilienfeld David , Gipp Pete , Gorczyca Thomas , Formica J. , Shen L. , Yamagami M. , Hillard Bob , Byrnes John
Published: October 2015

Silicon carbide (SiC) device fabrication technology shares many similarities with Si manufacturing, but identifying whether material differences affect cleaning capability is of interest for this growing field. Material parameter differences include diffusion coefficients, surface energy, and chemical bond strength, all of which can play a role in cleaning critical surfaces. This work compares trace surface contamination levels (as measured by TXRF) after 100 mm or 150 mm 4H SiC wafers underwent mercury-probe capacitance voltage (MCV) mapping, to levels after subsequent cleans. Trace levels of metals such as Hg, Fe, and Ni were controllably added during MCV, and it was shown that a variety of cleaning approaches can return the SiC surface to sub-5x1010 atoms/cm2 levels of cleanliness. Where these cleans fit into an integrated device process flow and comparison of cost are discussed.
Real-Time pH Monitoring of Ultra-Diluted Chemistry with a Micro-Sampling pH Monitor
Authors: Nakai Yoko , Miyamura Kazuhiro , Takagi So , Mori Yoshihiro
Published: October 2015

Real-time monitoring of pH and concentration estimation from pH data were studied using a newly developed micro-sampling pH monitor. Continuous monitoring of diluted ammonia solution with air and N2 bubbling clearly detected the real-time pH response to CO2 dissolution. With this new monitor, pH of low concentration ammonia, HF and BHF (HF and NH4F mixture) was measured and correlation to their respective concentrations was investigated. At <10 ppm, ammonia resolution was +/- 3 ppm and HF resolution was +/- 2 ppm. For BHF, when the NH4F concentration is provided by NIR concentration monitor, HF concentration resolution based on pH measurement was +/- 2 ppm. By utilizing this real-time pH monitoring technology, precise wet process control of diluted chemistry can be achieved.
(Invited) Computation-Driven Materials Search for Thermoelectric Applications
Authors: Hao Qing , Zhao Hongbo
Published: October 2015

The advancement of computational tools for material property predictions enables broad search of novel materials for various energy-related applications. However, challenges still exist in accurately predicting the mean free paths (MFPs) of electrons and phonons in a high-throughput frame for thermoelectric property predictions, which largely hinders the computation-driven search for novel materials. In this work, this need is eliminated under the small-grain-size limit, in which these MFPs are restricted by the grain sizes within a bulk material. The maximum ZT is anticipated when the grain size is reduced to the majority electron MFPs. Based on phonon dispersions and electronic band structures predicted by first-principles calculations, a ZT formulation for general nanograined bulk materials under the small-grain-size limit is proposed and is demonstrated with representative oxides.
(Invited) Thermoelectric Materials and Modules for High Temperature Application
Authors: Funahashi Ryoji , Barbier Tristan
Published: October 2015

A layered misfit Ca3Co4O9 shows high thermoelectric efficiency at high temperature in air. Thermoelectric modules using p-type Ca3Co4O9 and n-type CaMnO3 have been produced. The maximum power density reaches 4.3 kW/m2 at 973 K of the heat source temperature. A new n-type silicide material, Mn3Si4Al2 has been discovered. The dimensionless thermoelectric figure of merit reaches 0.21 at 773 K. This silicide shows good oxidation resistance at 873 K in air. Thermoelectric modules consisting of 64 pairs of legs have been fabricated using MnSi1.7 and Mn3Si4Al2 as p- and n-type legs, respectively. Output power reaches 9.4 W corresponding to 2.3 kW/m2 of power density at 873 K of the heat source temperature in air.
(Invited) The Landauer Approach to Electron and Phonon Transport
Authors: Maassen Jesse , Lundstrom Mark
Published: October 2015

In this paper we review the Landauer approach to electron, thermoelectric and phonon transport. We show how this formalism is physically intuitive, provides a common language for electrons and phonons, seamlessly spans from ballistic to diffusive transport regimes, supports materials of varying dimensionality (1D, 2D and 3D), and readily handles full dispersions and mean-free-path distributions with computational ease. There are two main quantities of interest which apply to both electron and phonon transport; the number of modes and the mean-free-path for backscattering. The former can be easily calculated from a material’s dispersion, while the latter depends also on the particular scattering physics. If both are known, all thermoelectric coefficients can be straightforwardly calculated and interpreted. The simple and physically intuitive form of the equations provides insight to enable the exploration of new materials, devices and electro-thermal applications.
(Invited) Tuning of Heat Transport across Thin Films of Polycristalline AlN via Multiscale Structural Defects
Authors: Jaramillo-Fernandez Juliana , Ordonez-Miranda Jose , Ollier Emmanuel , Sanatinia Reza , Kataria Himanshu , Chávez-Ángel Emigdio , Volz Sebastian , Sotomayor Torres Clivia M
Published: October 2015

The effective thermal conductivity of nanocrystalline films of AlN with inhomogeneous microstructure is investigated experimentally and theoretically. This is done by measuring the thermal conductivity of the samples with the 3-omega method and characterizing their microstructure by means of electron microscopy. The relative effect of the microstructure and the interface thermal resistance on the thermal conductivity is quantified through an analytical model. Thermal measurements showed that when the thickness of an AlN film is reduced from 1460 to 270 nm, its effective thermal conductivity decreases from 8.21 to 3.12 WŸm−1ŸK−1, which is two orders of magnitude smaller than its bulk counterpart value. It is shown that the size effects of the phonon mean free paths and the intrinsic thermal resistance resulting from the inhomogeneous microstructure predominate for thicker films, while the contribution of the interface thermal resistance strengthens as the film thickness is scaled down. The obtained results demonstrate that the structural inhomogeneity in polycrystalline AlN films can be efficiently used to tune their cross- plane thermal conductivity. In addition, thermal conductivity measurements of epitaxially grown InP layers on silicon using Raman spectroscopy are reported.
(Keynote) Devices Architectures and Technology for Quantum Computing
Authors: Kodera Tetsuo , Horibe Kosuke , Oda Shunri
Published: October 2015

There have been a lot of works on quantum computing hardware using various quantum two-level systems as a basic unit of information, which is called quantum bit (qubit). Especially an electron spin in a Si quantum dot (QD) is a well-defined quantum two-level system characterized by a spin-up and a spin-down state. This is one of the most promising candidates for a qubit, because of its long coherence time. The other advantage is that fabrication technology developed for integrated devices in Si can be applied. Toward Si spin qubits, we study physically-defined Si QD devices fabricated using metal-oxide-semiconductor (MOS) structures. We observe spin-related tunneling phenomena and reduce electron numbers in the QDs down to the few-electron regime. Charge detection of change in number of carriers in the QDs, one by one, has also been successfully demonstrated. These achievements are the important steps for realizing quantum computing devices.
(Invited) Gold-Induced Low-Temperature (<300°C) Growth of Quasi-Single Crystal SiGe on Insulator for Advanced Flexible Electronics
Authors: Sadoh Taizoh , Park Jong-Hyeok , Aoki Rikuta , Miyao Masanobu
Published: October 2015

A low-temperature (¡Ü300¡ãC) growth technique of quasi-single crystal, i.e., orientation-controlled large-grain (¡Ý10 ¦Ìm), Ge-related semiconductors, on insulator is desired for realization of advanced flexible electronics. To achieve this, we have developed the gold-induced layer-exchange crystallization technique using a-SiGe/Au stacked structures. By introduction of diffusion barrier with appropriate thickness into the a-SiGe/Au interface, (111)-oriented quasi-single crystal SiGe is achieved on insulating substrates at low temperatures (~300¡ãC). Based on these results, this technique is developed to formation of quasi-single crystal Ge on flexible plastic sheets. The grown layers have high carrier mobility, because residual Au hardly deteriorates the electrical properties of grown layers due to low solubility of Au in Ge. This technique will facilitate realization of advanced flexible electronics.
Gate-Bias Dependent Phonon Softening Observed in Ge MOSFETs
Authors: Kabuyanagi Shoichi , Nishimura Tomonori , Yajima Takeaki , Toriumi Akira
Published: October 2015

We investigate impacts of free carriers on phonon frequency of zone-center optical phonon in Germanium (Ge). By taking advantage of Ge-on-insulator structure, Raman measurement with applying the back-gate bias was performed. The phonon softening was clearly observed by increasing hole density. It is also pointed out that the phonon softening in heavily-doped Ge is mainly attributed to the free carrier effect rather than dopant atom one. Furthermore, we show that the free carrier effect on phonon softening can be simply and reasonably interpreted from the view point of modification of the covalent bonding by free carriers.
Biaxial Stress Evaluation in SiGe Epitaxially Grown on Ge Substrate by Oil-Immersion Raman Spectroscopy
Authors: Takeuchi Kazuma , Kosemura Daisuke , Yamamoto Shotaro , Tomita Motohiro , Usuda Koji , Sawamoto Naomi , Ogura Atsushi
Published: October 2015

Anisotropic biaxial stress states in the high-Ge concentration Si1-x
Ge
x
/Ge nanostructures were evaluated by oil-immersion Raman spectroscopy. Phonon deformation potentials (PDPs) are indispensable to convert the Raman frequency shift to stress in the Si1-x
Ge
x
. Therefore, we investigated the accurate PDPs (p and q) of the Si1-x
Ge
x
with the high Ge concentration by oil-immersion Raman spectroscopy. Using the derived PDPs, the clear uniaxial stress relaxation in the strained Si1-x
Ge
x
nanostructure was observed.
(Invited) Tunneling FET Technologies Using III-V and Ge Materials
Authors: Takagi Shinichi , Kim Minsoo , Noguchi Mitsuhiro , Nishi Koichi , Takenaka Mitsuru
Published: October 2015

We have demonstrated high performance operation of planar-type tunnel field-effect transistors (TFETs) using Ge/III-V materials. It is found that solid-phase Zn diffusion can realize steep-profile and defect-less p+/n source junctions. We have demonstrated the operation of high Ion/Ioff and low SS planar-type InGaAs tunnel FETs with Zn-diffused source junctions. The small S.S. of 64 mV/dec and large Ion/Ioff ratio over106 has been realized in the planar-type III-V TFETs. It is also shown that tensile strain in Si channels (sSi) combined with the Ge source can enhance the tunneling current because of the reduced effective energy bandgap. The fabricated Ge/sSOI (1.1 %) TFETs show high Ion/Ioff ratio over 107 and steep minimum subthreshold slope (SS) of 28 mV/dec.
(Invited) On the Electrical Activity of Extended Defects in High-Mobility Channel Materials
Authors: Simoen Eddy , Eneman Geert , Hikavyy Andriy Yakovitch , Loo Roger , Gupta Somya , Merckling Clement , Alian AliReza , Schulze Andreas , Caymax Matty , Langer Robert , Barla Kathy , Claeys Cor
Published: October 2015

The electrical activity of extended defects (dislocations; antiphase boundaries;...) in high-mobility channel materials (strained-Si; (strained)-Ge, GaAs and InGaAs) is investigated by means of simple device structures (p-n diodes and MOS capacitors). These are fabricated in substrates with a well-controlled density of predominant extended defects, enabling the determination of a specific leakage current contribution per defect. It is shown that there is a linear relationship between the area leakage current density and the threading dislocation density for a wide range of group IV p+n junctions. In the case of antiphase boundaries (APBs) of GaAs on Ge substrates, only a moderate electrical activity has been derived from these studies. On the other hand, a clear band of deep states has been demonstrated for TDs in InGaAs layers on GaAs substrates.
(Invited) Characterization of Individual Si/SiO2 Interface Traps: Direct Observation of Single P
b0 Centers by the Charge Pumping (CP) Method and Correction of the Conventional CP Theory
Authors: Tsuchiya Toshiaki
Published: October 2015

We made systematic measurements of the maximum charge pumping (CP) current (I
CPMAX) from single Si/SiO2 interface traps, and observed for the first time that their current range is 0<I
CPMAX≤2fq, but not a fixed value of fq, where f is the gate pulse frequency, and q is the electron charge. Although the conventional belief is that I
CPMAX is given by fqN, where N is the total number of traps contributing to the CP current, we experimentally clarified that this belief is basically wrong. Based on our results, we demonstrated fundamental trap-counting by the CP method. The current range 0<I
CPMAX≤2fq is expected from the nature of the P
b0 centers, therefore, the obtained results mean that we succeeded to directly and electrically observe single P
b0 centers, for the first time.
Photoemission Study on Chemical Bonding Features and Electronic Defect States of Thermally-Grown SiO2/4H-SiC Structure
Authors: Watanabe Hiromasa , Ohta Akio , Makihara Katsunori , Miyazaki Seiichi
Published: October 2015

Depth analysis of thermally grown SiO2/4H-SiC structure has been conducted systematically by high resolution x-ray photoelectron spectroscopy (XPS) and total photoelectron yield spectroscopy (PYS) to gain a better understanding of the energy band diagram and the energy distributions of the electronic defects. A SiO2 layer was grown on wet-chemically cleaned 4H-SiC surface by wet-oxidation at 1080 ºC. The energy band alignments have been evaluated by combination of the oxide bandgap values determined from energy loss spectra of O core level photoelectron with the valence band offsets obtained from valence band spectra. Depth profile of the defect states has been investigated from changes in the PYS intensity at each step of SiO2 thinning by dipping in a dilute HF solution. The photoelectron yield from filled defect states in the energy region corresponding to the 4H-SiC bandgap was significantly increased near the SiO2/4H-SiC interface.
Hydrogen Plasma Utilization in Advanced Logic Technology
Authors: Han Qiuhua , Meng Xiaoying , Zhang Haiyang
Published: October 2015

H2-based plasma process has been controversial for a long time as it’s reported the high H2-based plasma could result in device instability[1]. In this work, we investigated various H2 related etch processes in advanced logic technology from the point of view of selectivity, defect, reliability and yield performance. Due to the chemi-sorption and recombination of H atom at Si [2], high temperature(>250℃) H2 remote plasma can be used to minimize the material loss for process where oxygen is forbidden, while low temperature(<60℃) H2-based plasma process can be used in Si related etch processes with the improved selectivity to either mask or stop layer. Nevertheless, the low temperature H2 plasma directly contacting the exposed metal might result in plasma damage such as PID (plasma induced damage).