bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Cu-Doped Switching Layer of Amorphous Carbon-Oxide Based Reram on Non-Volatile Memory Characteristics for Forming-Free Operation
Authors: Park Jea-Gun , Kim Hea-Jee , Song Myung-JIn , Kwon Ki-Hyun , Kim Dong-Won , Jin Soo-Min , Kim Do Jun , Yang Hun-Mo
Published: February 2020

Resistive random access memory (ReRAM) is one of the candidates to alternate NAND flash memory due to its potential scalability, fast switching speed and low operating power [1]. However, for ReRAM in general, high-voltage forming process is needed to initiate the switching, which normally lead to high power consumption and operational complexity [2]. Therefore, the forming-free operation of ReRAM has been researched globally. In this work, to overcome this high voltage forming operation, the effect of Cu-doping on switching layer of amorphous carbon-oxide ReRAM was studied. ReRAM was fabricated with the structure of tungsten (W) / Cu-doped amorphous carbon oxide / hafnium oxide (HfO2) / platinum (Pt). The buffer layer, hafnium oxide, was inserted to decrease the current level increased excessively due to Cu-doping. It was confirmed that Cu-doping decreased forming voltage and increased memory margin. As comparing the characteristics of the ReRAM with and without Cu-doping at 34-nm pattern size, the forming voltage of Cu-doped ReRAM decreased from 2.7 to 1.95 V and also set voltage of that decreased a little from 1.8 to 1.65 V. From I-V characteristic graph, Cu-doped ReRAM demonstrated that the forming voltage was similar to the set voltage, indicating for the possibility of forming free operation. In addition, the memory margin of that was enlarged from 1.62×102 to 2.64×103. Besides, both of the devices had 106AC endurance cycles, which were excellent performance compared with other ReRAM devices. In our presentation, we report the effect of Cu-doping on electrical characteristics and the switching mechanism by using various analysis tools such as transmission electron microscopy (TEM).

* This material is based upon work supported by the Ministry of Trade, Industry & Energy (MOTIE, Korea) under Industrial Technology Innovation Program (10068055).

[1] Li Ji; Integrated one diode-one resister architecture in nanopillar SiOxresistive switching memory by nanosphere lithography. Nano Lett. 2014, 14, 813-818

[2] Ruomeng Huang; Forming-free resistive switching of tunable ZnO films grown by atomic layer deposition. Microelectron. Eng. 2016, 161, 7-12

Figure 1
Comparison of Low k Dielectric Film Properties Under Ultra Violet Curing Technique
Authors: Seshachalam Vijayalakshmi , Parker Alexander Robert , Yi Sang
Published: February 2020

Back End Of Line (BEOL) Low k Inter Layer Dielectric (ILD) films deposited using Plasma Enhanced Chemical Vapor Deposition (PECVD) processes are typically susceptible to mechanical and chemical damages after integration & downstream processes like Etching, Polishing etc. that raise reliability and packaging concerns. Addition of ultra violet (UV) curing enhances the film properties in terms of mechanical strength measured in modulus, hardness, adhesion energy of ILD to underlying film stack in addition to porogen removal & cross linking in ultra-low k films. This publication is intended to compare the low k and ultra-low k film properties as a function of UV cure with increments of UV curing time and intensity and different UV curing techniques. ILD stack properties are investigated from direct and indirect UV curing and positioning of UV curing in the film stack in a way to achieve desired mechanical strength & adhesion strength. Low k and Ultra low k films dielectric constant measurement comparison and correlation between traditional Mercury Probe and Surface Photo Voltage technique is presented. Effect of UV curing on the chemical bonding on low k and ultra-low k films are discussed using Fourier Transform Infra-Red (FTIR) Spectroscopy results.
Investigation of Degradation of Organometal Halide Perovskite Film and Solar Cell
Authors: Al Mamun Abdullah , Mohammed Yousuf , Ava Tanzila Tasnim , Baumgart Helmut , Elmustafa A A , Namkoong Gon
Published: February 2020

Organometal hybrid perovskite material has emerged as an attractive competitor in the field of photovoltaics due to its promising potential of low-cost and high-efficiency photovoltaic applications. Although organometal halide perovskite solar cell shows great potential to meet future energy needs, the degradation raises serious questions about its commercialization viability. At present, the stability of perovskite solar cells has been studied in various environmental conditions. Nonetheless, an understanding of the degradation and its performance of CH3NH3PbI3-xClx perovskite solar cell is limited.

Herein, we report the mechanical and structural degradation of CH3NH3PbI3-xClx perovskite films at room temperature as a function of time and thermal instability of perovskite solar cells during the heating and cooling processes. For mechanical degradation measurement, we used nanoindentation for CH3NH3PbI3-xClx perovskite films fabricated on FTO/PEDOT:PSS substrate. The hardness and elastic modulus of perovskite films were measured as a function of time. In addition, the mechanical degradation of perovskite thin films was correlated with X-ray diffraction, steady-state and time-resolved photoluminescence (PL). We also investigated the thermal instability of perovskite thin films and the irreversible performance of perovskite solar cells. Particularly, the irreversible performance of CH3NH3PbI3-xClx was analyzed by measuring the development of crystallinity, charge trapping/detrapping, trap depth, and PbI- phase while varying the temperature of perovskite films and solar cells between room temperature and 82 °C. Surprisingly, we found that the degradation of both perovskite films and solar cells occurred at ~70°C. Remarkably, even after the perovskite solar cell temperature cooled down to room temperature, the performance of solar cells continuously degraded. The underlying mechanism of irreversibly degraded performance of perovskite films and solar cells were explained in terms of the development of phase separation, increased trapping rates and deep trap depth of defect states of perovskite films.
Development of Sputter Processed Perovskite Films Toward Tandem Solar Cells
Authors: Raifuku Itaru , Ishikawa Yasuaki , Bourgeteau Tiphaine , Ito Seigo , Bonnassieux Yvan , Cabarrocas Pere Roca i , Uraoka Yukiharu
Published: February 2020

Tandem solar cells which combines several solar cells in series have been investigated to achieve high efficiency solar cells. Recently, perovskite/crystalline silicon tandem solar cells have attracted much attention as promising tandem structure because these solar cells have high external quantum efficiency in different wavelength range. There is a report on simulated efficiency of two terminal perovskite/crystalline silicon tandem solar cells. In that report, projected efficiency of over 30% is suggested by using inverted pyramid structure. However, most of perovskite solar cells are fabricated by solution process which is not suitable way for textured substrates, indicating that it is difficult to achieve such structured tandem solar cells in current conventional process. To overcome this problem, we focused on sputtering process. Sputtering can achieve homogeneous films even the substrate has large roughness such as textured substrates. Therefore, it is expected that sputtering is suitable method to achieve high efficient tandem solar cells. In addition, there are no reports on sputtered perovskite films which are used for solar cells. In this work, we fabricated perovskite films by sputtering and investigated the characteristics.

In this work, we tried to fabricate CH3NH3PbI3 perovskite films which is commonly used as light absorber. The perovskite films were obtained from sputtered PbI2 films. PbI2 sputtering target was fabricated from PbI2 powder using a pressing under 10 MPa on stainless plate. Then, PbI2 films were deposited on glass substrates by RF sputtering using the PbI2 target. The sputtering condition was Ar atmosphere, under 1 Pa at room temperature. Perovskite films were obtained by reacting sputtered the PbI2 films and CH3NH3I gas in petri dish. The obtained perovskite films were characterized by X-ray diffraction (XRD) measurement and scanning electron microscopy (SEM) observation.

 Figure 1 shows XRD pattern of a perovskite film obtained from sputtered PbI2 film. Sputter processed perovskite films showed typical diffraction patterns of CH3NH3PbI3 perovskite films and had similar peaks to solution processed perovskite films.

Figure 2 shows a cross sectional SEM image of a PbI2 film sputtered on fluorine-doped tin oxide (FTO) and TiO2 coated glass substrate. This image clearly indicates that homogeneous PbI2 and/or perovskite films could be fabricated by sputtering even if the substrates have large roughness. This result suggested sputtering is promising process to achieve high efficiency tandem solar cells.

Figure 1
Ni Alloy Monolayer Electrodeposition
Authors: Allongue Philippe , Maroun Fouad , Damian Alexis , LeCadre Florian
Published: February 2020

The morphology and the microstructure of alloys grown by co-electrodeposition generally result from kinetics and depart from equilibrium. On the atomic scale key parameters include binding energies (e.g. adatom – surface, adatom – adatom etc.) and also on adatom mobility.

 In this presentation we will examine the impact of above parameters on Ni alloy monolayers electrodeposition. An unreconstructed AuPd(111) substrate is used to co-deposit Ni and Ag, Au [1] and Pd [2]. These elements were chosen because they present different bulk mixing enthalpies with Ni, from phase separation (Ag) to perfect mixing (Pd). These three elements present also quite different surface mobility. Complementary experiments in which the two metals are sequentially deposited [3] [4] as well as dealloying experiments (selective dissolution of Ni) [5] will be presented in support of discussion. References :

[1] F. Lecadre et al. AuNi alloy monolayer films electrodeposited on Au(111): An in situ STM study, Surf. Sci. 607, 25 (2013).

[2] A. Damian et al. Electrodeposition of NiPd monolayer on Au(111): An in situ scanning tunneling microscopy study, Electrochim. Acta 112, 824 (2013).

[3] A. Damian et al. Selective Growth and Dissolution of Ni on a PdAu Bimetallic Surface by In Situ STM: Determining the Relative Adsorbate-Substrate Interaction Energy, Phys. Rev. Lett. 102, 196101 (2009).

[4] F. Lecadre et al. Electrodeposition of Ag, Pd and Au on Ni monolayer islands on (1 × 1)-Au(111) by in-situ scanning tunneling microscopy, Electrochim. Acta 197, 241 (2016).

[5] A. Damian et al. Electrochemical de-alloying in two dimensions: role of the local atomic environment, Nanoscale 8, 13985 (2016).
Electrodeposition of Nickel on Titanium in Aqueous Acidic Electrolytes
Authors: Jensen Mats , Haarberg Geir Martin , Seland Frode , Sunde Svein , Ratvik Arne Petter
Published: February 2020

Nickel may be produced in acidic chloride-sulfate based electrolytes. Nickel is initially deposited on stainless steel or titanium cathodes to produce starting sheets while chlorine gas is evolved on DSA anodes. Stress in the nickel deposit may cause bending of the cathode sheet. In addition, irregular growth such as dendrite formation may occur. In extreme cases, short-circuiting of electrodes will happen. Fundamental electrochemical studies of the initial stages of the electrodeposition process may give valuable information for obtaining smooth nickel deposits.

Electrochemical experiments of nickel deposition were carried out on titanium substrates using cyclic voltammetry and potential step, and examined with SEM imaging. The measurements were performed at different deposition potentials and times to get an overall picture of the nucleation and growth of nickel on titanium substrates. Further deposition studies have been performed using in situ AFM to study the whole process from single nickel nuclei to a cohesive layer, and determine the nucleation mode and characteristics. The effects of electrolyte composition and pH will be presented.

The pre-treatment of the substrate is important for the nucleation and properties of the nickel deposit. The figure illustrates the different nucleation overpotential for a smooth and rough titanium substrate.

Figure 1
Color Measurements and Development in Electroplating Trades
Authors: Giurlani Walter , Freschi Stefano , De Luca Antonio , Giaccherini Andrea , Innocenti Massimo
Published: February 2020

The color measurement is a fundamental step in quality control at the end of the assembly line and in the research and development process for a variety of industrial fields: printings, textiles, automotive and last, but not least, electroplating. The precise color determination and realization has a central importance in the fashion division of electroplated bijoux. Even if color measurement could appear to be a simple operation, that’s not the case. Indeed, variation in surface roughness, ambient illumination, instruments and methods could affect drastically the reproducibility of analysis. Often, especially in industrial environment, these variables are underestimated resulting in communication problems between producer and customer. The purpose of this study, focused on the fashion applications, is to take an overview of conditions and techniques of color evaluation, effectively implemented from companies, and to find out the most accurate, and at the same time economically sustainable one. To reach this goal all the measurements are taken by keeping in mind the CIE’s (Commission Internationale de l’Eclairage - International Commission on Illumination) recommendations about standard observers, illuminants and operative conditions for reflective samples. The accuracy and affidability of a commercial colorimeter, general used in quality control, have been evaluated by comparison with a much more expensive UV-VIS laboratory spectrophotometer, which provides exact results. All specimens have been prepared by electrodeposition from different standards solutions commonly used in the electroplating area. Furthermore, is object of the study also the diverse colors obtained from the same electroplating bath by changing the operating condition, like pH, current density, additives, as well as metal ions composition.
Aging Mechanisms in Electrodeposited Cobalt-Hardened Gold Coatings
Authors: Banga Dhego
Published: February 2020

Electrodeposited cobalt-hardened gold (Au(Co)) coatings are used on electrical connectors and contacts requiring resistance to mechanical wear as well as low electrical contact resistance. However, conventionally electrodeposited Au(Co) films grown using direct current (DC) electroplating method possess complex, porous microstructures. An open question is how this porosity affects the susceptibility of these coatings to potential electrical and mechanical failure. To test the hypothesis that microstructural voids degrade the coating stability, we conducted an elevated temperature aging study to compare Au(Co) grown with a void microstructure, using conventional deposition processes, with Au(Co) grown without a void microstructure, using a new pulsed-plating process developed at Sandia national laboratories. Using characterization techniques including scanning electron microscopy, transmission electron microscopy, transmission Kikuchi diffraction, atomic force microscopy, sheet resistance measurements, nanoindentation, and atom-probe tomography, we will demonstrate how porous coatings degrade by coarsening of voids, reactions of coatings with substrates, and diffusion of the hardening agent Co from the film to the substrate/coating interface with increased annealing temperature which in turn negatively affect the coatings’ structural integrity and the stability of electrical and mechanical properties. In contrast, we will show that non-porous Au(Co) coatings display stable low resistance, surface morphology, interface with substrates, and no development of voids or diffusion of Co in the microstructure with increased annealing temperature.

Figure 1
The Effect of Levelers on Plating through Holes of a PCB By Using Reduced Graphene Oxide (rGO) As a Conducting Layer
Authors: Chang I-Hsuan , Dow Wei-Ping
Published: February 2020

Electroless (ELS) copper plating process has been commonly used in the metallization process of printed circuit boards (PCBs), because the sidewalls of the through holes (THs) of PCBs are composited of resin and glass fiber, which are not conductive materials. Hence, before plating these THs, their sidewalls have to be metallized by ELS copper plating. The process causes harmful influence to environment because it contains precious metal (i.e., Pd as a catalyst), formaldehyde and chelating agents. However, reduced graphene oxide (rGO) grafting process, proposed in this work, is environment-friendly and can replace the ELS copper plating process to make the sidewall of the TH of a PCB be conductive for copper electroplating. The rGO grafting process has less steps and an environment-friendly formulation. In this work, the rGO is grafted on the sidewalls of THs of a PCB with a high aspect ratio (AR). We observed that the copper nucleation mechanism of electrochemical deposition on a PCB is progressive. In addition, we studied the suppression of various levelers on copper electrodeposition in order to control the copper to be less deposited at the hole opening but much more deposited at the hole center. Finally, the throwing power (TP) of the copper electrodeposition in the TH can be significantly enhanced.

In our research, the effects of electroplating baths, operating parameters and electroplating additives, especially levelers, were investigated for obtaining a high TP of THs. On the other hand, the suppression of various levelers was evaluated by electrochemical analysis, such as linear sweep voltammetry (LSV) and galvanostatic measurements. The results indicate that the electroplating bath containing the leveler with stronger suppression can control the copper to be specifically deposited at the hole opening. Hence, a high TP of plating TH was achieved by using the rGO process. Moreover, the plated TH can pass thermal shock test. That means, a brand-new and promising rGO process can replace the ELS copper plating in the future for producing advanced electronic products.
Electrodeposition of Germanium at Elevated Temperatures and Pressures from Ionic Liquids
Authors: Fransaer Jan , Wu Minxian , Binnemans Koen
Published: February 2020

The electrodeposition of germanium at elevated temperatures up to 180 C and pressures was studied from the ionic liquids 1-butyl-1-methylpyrrolidinium dicyanamide and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide containing [GeCl4(BuIm)2] (where BuIm = 1-butylimidazole) or GeCl4. Cyclic voltammetry (CV), electrochemical quartz crystal microbalance (EQCM), rotating ring-disk electrode (RRDE), scanning electron microscope (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), electron backscatter diffraction (EBSD) and Auger electron spectroscopy (AES) were used to investigate the electrochemical behavior and the properties of the electrodeposited germanium. Electrodeposition at elevated temperatures leads to higher deposition rates due to: (1) increase in the diffusion rate of the electroactive germanium compounds; (2) faster electrochemical kinetics in the electrolyte; and (3) higher electrical conductivity of the electrodeposited germanium film. Moreover, the morphology of the germanium film is also of a better quality at higher electrodeposition temperatures due to an increase in adatom mobility.
Electrochemical Formation of Dy and Nd Alloys Using Liquid Metal Electrodes in Molten LiCl-KCl Systems
Authors: Konishi Hirokazu , Ono Hideki , Nohira Toshiyuki , Oishi Tetsuo
Published: February 2020

We proposed new separation and recovery process for RE metals from Nd magnet scraps using molten salt electrolysis and an alloy diaphragm. This new process was first applied to chloride melts, and the separation of Dy and Nd were investigated using Ni cathodic electrodes in molten LiCl-KCl-DyCl3-NdCl3 systems. The highest mass ratio of Dy/Nd in Dy-Nd-Ni alloy samples was found to be 72.

We focused on the liquid metals as the alloy diaphragms. Liquid metals have higher diffusion rates of elements than those of solid metals during the electrolysis. In this work, Bi, Sn and Zn electrodes were used as liquid metal electrodes. The alloy samples were prepared by potentiostatic electrolysis using liquid Bi, Sn and Zn electrodes in molten LiCl-KCl added DyCl3(0.50 mol%) and NdCl3(0.50 mol%) at 723 K.
Layered-to-Spinel Phase Transformation of Li2MnO3 during the Initial Charge
Authors: Shimoda Keiji , Matsunaga Toshiyuki , Murakami Miwa , Arai Hajime , Uchimoto Yoshiharu , Matsubara Eiichiro , Ogumi Zempachi
Published: February 2020

Lithium- and Manganese-Rich layered oxides (LMRs) are one of the promising candidates of positive electrode materials for the advanced LIB due to their high reversible capacities. The chemical formula is often described as xLi2MnO3•(1–x)LiMO2 that consists of Li2MnO3- and LiMO2-rich nano-domains. The LMR-based electrodes show a voltage plateau at ca. 4.5 V in the initial charge process, which leads to an irreversible capacity. This plateau is understood to appear for the activation of Li2MnO3.[1,2] This activation process is not thoroughly understood yet and the elucidation of this reaction would lead to the practical use of this material. Some groups have reported that the charge compensation on the delithiation from Li2MnO3 is associated with the oxidation of oxide ion including O2release from the structure.[3,4] The present work focuses on clarifying the structural changes taking place inside LMR bulk at the initial delithiation (charge) using SR-X ray diffraction, STEM, and solid-state NMR.[5]

SR-XRD profiles showed that all the diffraction intensities were gradually decreased and broadened during the initial charge up to 4.8 V, which indicated that the initial delithiation caused the change to highly disordered material. The high-resolution 6Li MAS NMR spectra showed that Li+ was monotonously extracted from both the Li and TM layers. EELS mapping by STEM suggested that the Li+extraction from the sample of 50% SOC occurred in a biphasic manner inside a single particle. The lattice structures of the active material after charge-discharge cycle was also examined on samples at the 20th discharged and 21stcharged states.

This work was supported by the Research and Development Initiative for Scientific Innovation of New Generation Batteries (RISING) and the Research and Development Initiative for Scientific Innovation of New Generation Batteries II (RISING II) projects from the New Energy and Industrial Technology Development Organization (NEDO), Japan.

[1] Thackeray et al., J. Mater. Chem., 2007, 17, 3112.

[2] Yu & Zhou, J. Phys. Chem. Lett., 2013, 4, 1268.

[3] Yu et al., J. Electrochem. Soc., 2009, 156, A417.

[4] Oishi et al., J. Mater. Chem. A, 2016, 4, 9293.

[5] Shimoda et al., J. Mater. Chem. A, 2017, 5, 6695.
Development of Micro-Capillary and Micro-Pouch Cells for in-Operando Observation of Dendrites and Electrodeposition Using Ultra High Resolution X-Ray Imaging
Authors: Choi Paul , Frisco Sarah , Litster Shawn
Published: February 2020

Lithium dendrite formation inside lithium-ion batteries with graphite anodes and beyond-lithium-ion batteries with metal anodes has shown to dramatically limit cycle life, restrict windows of operating conditions, and can result in catastrophic failures. Numerous research efforts have been and are still being dedicated to characterizing dendritic electrodeposition in batteries, yet the phenomenon remains to be fully understood. Our work aims to characterize the nucleation and growth of dendrites in batteries via in-operando observation using nanoscale x-ray radiography and computed tomography (nano-CT). Figure 1 shows our results using an in-house micro-capillary cell to observe in-operando the galvanostatic electrodeposition of copper in a symmetrical aqueous copper cell. In this cell, the electrode is coated on a metal micro-wire current collector and is immersed in a liquid bath of electrolyte. Such in-operando experiments allow for simultaneous observation of structure and voltage response as shown in Figure 1f, from which structural evolution can be correlated to cell voltage. In practical applications, an important aspect of dendritic failure is the interaction of electroplated Li with the electrolyte separator. To evaluate these interactions, we have developed a novel planar micro-pouch cell with commercial separator materials for in-operando observation at up to 50 nm resolution. Compared to the micro-capillary cell, which was used to produce the results shown in Figure 1, the new micro-pouch cell offers increased control of the active material loading and capacity, increased flexibility in component material selection, and easier assembly.

Figure 1
(Invited) Wetting, Adhesion and Stiction of 2D Materials
Authors: Mertens Stijn F. L.
Published: February 2020

The wetting properties of surfaces, including the adhesion and stiction (static friction) of liquid drops, are critical for processing materials and post-production problems such as fouling. With the emergence of 2D materials such as graphene and hexagonal boron nitride, the interaction of liquids with one-atom-thick matter and its support poses new challenges in our understanding of wetting.

In my talk, I shall present an overview of recent research in this area, ranging from wetting transparency and translucency of graphene [1,2] to electrochemically switchable wetting and adhesion of hexagonal boron nitride [3].

[1] J. Rafiee, X. Mi, H. Gullapalli, A.V. Thomas, F. Yavari, Y.F. Shi, P.M. Ajayan, N.A. Koratkar, Nat. Mater. 11 (2012) 217–222.

[2] C.J. Shih, M.S. Strano, D. Blankschtein, Nat. Mater. 11 (2013) 866–869.

[3] S.F.L. Mertens, A. Hemmi, S. Muff, O. Gröning, S. De Feyter, J. Osterwalder, T. Greber, Nature 534 (2016) 676–679.

Figure: Electrochemical hydrogen intercalation flattens a monolayer of hexagonal boron nitride on Rh(111) and changes advancing (1) and receding (2) contact angles

Figure 1
Characterization of Ammonium Silicate Residue during Polysilazane (PSZ) Dry Etching in NF3/ H2O Gas Chemistry
Authors: Kim Hyun-Tae , Kim Min-Su , Lee Jong-Seok , Choi Geun-Min , Park Jin-Goo
Published: February 2020

For 28nm NAND flash memory, the aspect ratio of shallow trench isolation (STI) becomes large, and it makes difficult to fill STI structure by conventional oxide film without void formation. Several gap-fill methods such as high density plasma (HDP) and thermal chemical vapor deposition (CVD) are widely accepted, but they are difficult to make gap fill without void because of gap-fill margin. Recently, STI fill has been tried with polysilazane (PSZ) based inorganic spin-on dielectric (SOD) film. PSZ oxide has its good gap-fill ability, low moisture content and high etching resistance. However, PSZ oxide would produce amine etch residue during the NF3 dry etching process because of NH3component in PSZ oxide. For preventing this resudue, it is very important to control process parameters affecting the chemical reaction because the etch rate, and the surface quality depend upon the process reaction. During the STI etching back process, other layer also exposed. So, selectivity between other oxide must be considered.

 In this study, we have employed plasma dry etching of nitrogen trifluoride (NF3) and H2O mixtures. We studied the effect of the gas chemistry on the etching of oxides. The materials used for these experiments were thermally grown SiO2 (1000Å, 10000Å), PSZ oxide (500Å), TEOS (315Å) and ALD oxide (300Å). Samples of size 25 x 25 mm were cleaned first in diluted SC-1 [NH4OH(25%): H2O2(38%): DIW =1:2:50] at 60°C for 10 min. The etching mechanism of PSZ oxide was investigated in plasma activated NF3/H2O gas. This process generates ammonium hexafluorosilicate ((NH4)2SiF6) as a by-product. By-products were formed on the PSZ surface which was confirmed by observing N–H, NH4+ and SiF6
2-peak in ATR-FTIR spectrum. These peaks are representative of (NH4)2SiF6 powder composition. Etch rates of several SiO2 were reported as a function of H2O ratio, substrate temperature, and pressure. NF3/H2O mixtures were excited using pulsed RF plasma. The NF3 flow rate for all experiments was kept at 150 sccm. The temperatures were varied from 8 to18ºC, the chamber pressures from 7 to 9 Torr., the H2O flow rates from 1500 to 2500 sccm and process times from 20 to 100 sec. Helium was used as a carrier gas. After dry etching, an annealing process was performed. The reaction mechanism was proposed by analyzing the oxide layer surface. We used an ellipsometer to measure the oxide thickness for evaluation of the etch rate. Also, various analyzing tools such as SEM, contact angle analyzer, and FT-IR were used to characterize the surface contaminants. The optimized drying process provides the high selectivity without any residue formation.
(Invited) Photo-Assisted ALD: Process Development and Application Perspectives
Authors: Miikkulainen Ville , Väyrynen Katja , Kilpi Väinö , Han Zhongmei , Vehkamäki Marko , Mizohata Kenichiro , Räisänen Jyrki , Ritala Mikko
Published: February 2020

Photons can be utilized to create new ALD chemistry or enhance existing ALD processes. Photo-enhancement provides many potential advantages such as lower deposition temperature, novel growth chemistries, selective area deposition, and improvement of film properties. Despite these attractive advantages, there are not many reports available on the topic, materials deposited being mostly oxides, e.g. ZnO, Al2O3 and Ta2O5.[1-3] The main challenges are the reactor design and the complexity of photochemistry in the heterogeneous system. The reactor must ensure intensive light of appropriate wavelength on the substrate while avoiding film growth on the optical components. On the other hand, optical properties of the adsorbed precursor, the substrate, and the film can all contribute to the deposition photochemistry.

We have been studying and developing photo-assisted ALD processes for oxide and metal thin films. A customized Picosun™ R-200 ALD reactor with two alternative UV sources has been employed. A single-source approach with metal alkoxides has proved itself an effective method for depositing Ti, Zr, Hf, Nb, and Ta oxides.[4] Area-selectivity of the photo-assisted Ta2O5 ALD was demonstrated by depositing a University of Helsinki emblem with two aluminum shadow masks (Fig.1). Resolution does not allow device level patterning but can be exploited to protect contact areas, for example. The photo-assisted ALD of metals is fundamentally different from the case of oxides in that the deposited material is optically absorbing and electrically conductive. Furthermore, the metal typically needs to be reduced during the ALD cycle. In this presentation, results on process development and the material properties of photo-assisted ALD of metal oxides, and Ru and Cu will be discussed, together with potential applications in sight. Focused ion beam patterning, wet etching and pre-patterned substrates can be used to demonstrate the capabilities of photo-ALD films.

The Semiconductor Research Corporation (SRC) and Finnish Centre of Excellence in Atomic Layer Deposition (ALDCoE) are acknowledged for funding. Picosun provided the customized reactor for the project.

References

[1] Yamada, A.; Sang, B.; Konagai, M. Appl. Surf. Sci.
1997,
112,216.

[2] Lee, Y.-H.; Kwak, J.-C.; Gang, B.-S.; Kim H.-C.; Choi, B.-H.; Jeong, B.-K.; Park, S.-H.; Lee, K.-H. J. Electrochem. Soc.
2004, 151, C52.

[3] Chalker, P. R.; Marshall, P. A.; Dawson, K.; Brunell, I. F.; Sutcliffe, C. J.; Potter, R. J. AIP Advances
2015, 5, 017115.

[4] Miikkulainen, V.; Väyrynen, K.; Kilpi, V.; Mizohata, K.; Räisänen, J; Ritala, M., manuscript.

Figure 1
Insights Towards Mitigated Mn Dissolution through Structure-Sensitive Al2O3 Film Nucleation on LiMn2O4 By Atomic Layer Deposition
Authors: Warburton Robert , Chen Lin , Voeroes Marton , Iddir Hakim , Chen Kan-Sheng , Liberia Joseph , Hersam Mark C. , Curtiss Larry A , Elam Jeffrey W , Greeley Jeff
Published: February 2020

Dissolution of transition metal (TM) cations into organic electrolytes is a significant impediment to capacity retention in various lithium ion battery electrode materials. Interfaces engineered via substitutional doping and protective coatings, however, have been demonstrated to be effective techniques to reduce TM dissolution, preventing counterelectrode crossover1–3. In this work, we present an integrated theoretical and experimental approach to gain a molecular level understanding towards the functionality of protective thin films. As a model system, we consider Al2O3 film growth by atomic layer deposition (ALD) on spinel LiMn2O4 (LMO), a cathode material exhibiting the well-documented capacity fade mechanism of Mn dissolution. Using first principles DFT+U calculations in concert with in situ experimental characterization, the mechanisms for Al2O3 ALD film growth by trimethylaluminum (TMA) and H2O half-reactions are evaluated. Using thermodynamically stable low-index surface truncations, as well as stepped defect features4, we identify facile pathways for full demethylation of the TMA precursor on the LMO surface. Trends from microbalance experiments indicate sub-monolayer film coverage for ~10 ALD cycles, wherein film growth is initially slow, but gradually increases until the limit of a fully formed Al2O3 film is reached. DFT calculations suggest that sluggish film growth at the onset is predicated by site blocking from decomposed CH3 groups. An electronic structure descriptor is presented to demonstrate evidence that, in early ALD pulses, Al2O3 preferentially nucleates at sites on LMO that are most susceptible to Mn dissolution. The chemical nature of these relevant defect sites will be discussed further in the context of Mn dissolution through charge disproportionation, with enhanced stability by selective nucleation of the protective films. The unique mechanisms for ALD on LMO lead to modest enhancements in electrochemical performance for only ~1-2 ALD cycles, whereas cycling capabilities reduce with further TMA/H2O pulses in the limit of a fully formed coating on the substrate.

This research was supported as part of the Center for Electrochemical Energy Science, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
Optimizing Process Parameters for Plasma Assisted Atomic Layer Deposition
Authors: Boris David R. , Wheeler Virginia D. , Anderson Virginia R , Nepal Neeraj , Rosenberg Samantha G , Kozen Alex C , Hite Jennifer K , Walton Scott G , Eddy Charles R.
Published: February 2020

Plasma assisted atomic layer deposition (PA-ALD) is a low temperature conformal layer-by-layer deposition technique that is based on a pair of self-terminating and self-limiting gas-surface half-reactions, in which at least one half-reaction involves species from a plasma. This approach generally offers the benefit of substantially reduced growth temperatures and greater flexibility in tailoring the gas phase chemistry to produce varying film characteristics. The flexibility and lower growth temperatures that plasmas provide come at the cost of a complex array of process variables that often require great care on the part of the user.
In response to this challenge, this work focuses on the use of plasma diagnostics to inform the choice of process conditions for PA-ALD systems. In this work we employ optical emission spectroscopy and charged particle collectors to characterize a Fiji 200 (Ultratech/CNT) PA-ALD tool. In particular, we assess the total ion flux reaching the substrate surface and the relative fractions of atomic and molecular species generated in the plasma under a variety of pressures and gas input flow fractions in the context of PA-ALD of AlN and Ga2O3films. Changes in plasma parameters are then linked with changes in film characteristics.
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* This work supported by the Naval Research Laboratory Base Program
Interfaces Formed by ALD Metal Oxide Growth on Metal Layers
Authors: Aussen Stephan , Hardtdegen Alexander , Skaja Katharina , Hoffmann-Eifert Susanne
Published: February 2020

Redox-based resistive switching random access memory (ReRAM) has the potential to fulfill the demands of future Green IT solutions for non-volatile memory circuits with high speed data access, high reliability, and low power consumption. A single valence-change-mechanism (VCM)-type switching cell is typically built from a transition metal oxide layer sandwiched between metal electrodes of different oxidation enthalpy. It is accepted in the scientific community that oxygen exchange and drift/diffusion processes play a major role in the resistive switching process. Thus, understanding oxidation/reduction reactions taking place already during the growth process is of utmost importance.

For future three-dimensional (3D) integrated arrays of ReRAM cells atomic layer deposition (ALD) will become the method of choice to grow ultra-thin, conformal, homogeneous and dense oxide films at a thermal budget below 450 °C. For todays’ two dimensional stacked crossbar arrays, the metal oxide films can be grown on nearly inert Pt electrodes, while the oxygen exchange layer built from a reactive metal is deposited on top of the metal oxide. However, in the 3D ReRAM arrays the metal oxide might need to be grown on the reactive metal as well.

In this study ultrathin ALD metal oxide layers are deposited on various metal electrodes by means of in-situ transfer from the sputtered metal into the ALD chamber. For the metal layers we utilized Pt, Hf, and Ta while for the metal oxides Al2O3, TiO2, and HfO2 were chosen. ALD metal oxide processes were performed by plasma assisted ALD in an Oxford FlexAlâ system.

Due to the passivation property of the dense ALD metal oxide layer the metal oxide / metal interfaces could be analyzed ex-situ if the vacuum break was kept short. Angle resolved X-ray photoemission spectroscopy studies combined with X-ray reflectivity analysis reveal a clear picture of the interface formation and the oxygen gradient formed at the interface already during growth. The influence of process parameters and stack sequences on this ‘built-in’ oxygen gradient at metal / ALD metal oxide interfaces will be covered in this presentation. Among others, the possibility for PtOx formation during remote oxygen plasma ALD processes will be discussed.
The Effect of Low Temperature Annealing on the Deactivation and Defect Formation in Highly Doped Si:P Epitaxially Grown Films
Authors: Weinrich Zach , Brown David Lee , Atassi Amalie , Li Xuebin , Sharma Shashank , Chung Hua , Jones Kevin Scott
Published: February 2020

Highly-doped Si:P (HDSiP) epitaxially grown thin films with P concentrations above 1021 cm-3 are being investigated for transistor applications due to their ability to achieve record-setting low nMOS contact resistance junctions suitable for the ITRS 7 nm technology node. Efficient dopant activation of these HDSiP layers with negligible diffusion have been reported by using an Applied Materials AstraTM millisecond laser dynamic surface anneal (DSA). This work investigates the stability of the dopant activation in these HDSiP layers during subsequent post-DSA thermal processing via Hall effect measurements. The corresponding structural changes in the HDSiP films are investigated using cross-sectional transmission electron microscopy (TEM). 40 nm thick epitaxial layers were grown with chemical doping concentrations between 0.3 – 4.0 x 1021 cm-3. Subsequent DSA treatment at 1200 °C leads to electrical dopant activation of 1 x 1021 cm-3. Subsequent low temperature annealing between 700 °C and 900 °C for times up to 30 minutes resulted in significant electrical deactivation. TEM examination shows these films are defect free after DSA treatment but for higher concentrations, extended defect formation in the epitaxial film was observed. These extended defects appear to be in the form of dislocation loops and may be the byproduct of point defect release during deactivation. The mechanism involved in deactivation will be discussed.
The Improvement of the Pattern Wiggling Profile by Photo Resist Treatment
Authors: Liu Pan-Pan , Zhang Cheng-Long , Zhang Hai-Yang
Published: February 2020

Abstract

For advanced node such as 14nm technology and beyond, Patterning is one of the key challenges in the semiconductor industry. Advanced pattern transfer techniques such as negative tone development (NTD) technology are under investigation to enable the aggressive pitch requirements demanded. Even though, just as traditional positive tone development (PTD) technique, a pattern wiggling issue has arisen with the reduction of pattern dimension during dry etch process, which prevents the successful pattern transfer [1].

Two kinds of wiggling solutions have been proposed. One is the lithographic resolution such as changing the physical properties of the under-layer materials [2-4]. The other is the gases treatment in the tri-layer process such as H2plasma for spin-on carbon (SOC) hard-mask [5] and HBr and Ar plasma treatment for photoresist [6]. However, with the decrease of device size, a single method hardly eliminates wiggling and meets the pattern target. Besides, the requirements for Line Edge Roughness (LER)/Line Width Roughness (LWR); critical dimension uniformity (CDU); through pitch are extremely aggressive in advanced technology. Therefore, the characteristics of the dry etching process play an increasingly import role in defining the outcome of the pattern process.

In this paper, we will demonstrate the method of PR treatment (both PTD and NTD techniques) that improves LER/LWR for trench pattern in dry etch ICP etcher. Meanwhile, the difference of PR treatment methods between PTD and NTD is illuminated. What’s more, in PR treatment methods, other pattern behavers such as CD, CD uniformity, through pitch are concerned during improving LER/LWR process, and aim to get a good result of all aspects. At last, the role of various plasma etch parameters that influence the key patterning metrics of CD, resist selectivity and LER/LWR are studied.

Acknowledgement

REFERENCES

[1] Goji Wakamatsu, Kentaro Goto, Yoshi Hishiro, Taiichi Furukawa al., Advances in Resist Materials and Processing Technology XXIX, Proc. of SPIE Vol. 8325 83250T-1,(2012)

[2] Makoto, M., Mitsuaki, I., Takashi, K., Hisashi, H, and Seiji, F., Proc. SPIE7972,797226 (2011).

[3] Tadokoro M., Yonekura K., Yoshikawa K., Ono Y., Ishibashi T., Hanawa T., Fukiwara N., Matsunobe T., MatsudaK., J. Vac. Sci.Technol. B,26, 67-71 (2008).

[4] Someya, Y., Shinjo, T., Hashimoto, K., Nishimaki, H., Karasawa, R., Sakamoto, R., Matsumoto,T., Proceedings of the SPIE, vol.8325, 83250U (2012).

[5] M. Tadokoro, K. Yonekura, K. Yoshikawa, Y. Ono, T. Ishibashi,T. Hanawa, and N. Fujiwara, J. Vac. Sci. Technol. B 26 (1) Jan/Feb( 2008)

[6] E. Pargon, K. Menguelti, M. Martin, A. Bazin, O. Chaix-Pluchery, C. Sourd, S. Derrough, T. Lill, and O. Joubert, Journal of Applied Physics 105, 094902 (2009)
(Invited) Growth and Applications of Si1-xSnx Thin Films
Authors: Kurosawa Masashi , Nakatsuka Osamu , Zaima Shigeaki
Published: February 2020

Integration of near-infrared light source/detector on Si chips has long been expected to achieve on-chip and/or chip-to-chip optical interconnectivity. However, the indirect band gap of group-IV semiconductor such as Si and Ge remains a challenge especially for photoemission. Although the direct band gap in Si is 3.1 eV above the indirect band gap and the solid solubility limit of Sn in Si is extremely low (0.1%), the Si1-xSnx alloys must have a direct band gap for a sufficiently high Sn content, as for Ge1-xSnx. From a device perspective, an experimental demonstration of the band gap is desired. However, the relevant optical property for Si1-xSnxhas to date not been obtained.

Under such a background, the present paper reports our recent progress in advanced low-temperature crystallizations for Si1-xSnx (x: 0–0.4) thin films on various substrates (insulators, Si, Ge, InP, etc.). Composition analyses indicate that approximately 20% of the Sn atoms are substituted into the polycrystalline (or epitaxial) thin films grown on an insulator (or Ge(001)) after annealing at 220 oC for 5 h. By using InP(001) substrates, the Sn content could raise up to about 40%. Comparison of the band gap with the calculated values and new applications, such as Si1-xSnx-source tunnel field effect transistors and thermoelectric generator, will be discussed.

Acknowledgments

This work was partially supported by Grants-in-Aid for Scientific Research (S) (Grant No. 26220605) and Young Scientists (A) (Grant No. 17H04919) from JSPS in Japan and PRESTO (Grant No. JPMJPR15R2) from JST in Japan.
(Invited) Ultrapure Homoepitaxial Diamond Films Grown by Chemical Vapor Deposition
Authors: Teraji Tokuyuki
Published: February 2020

In this decade, studies on semiconducting diamond for the power device application have intensively been conducted in several research groups. A use of diamond crystals with low defect density is crucial for obtaining high blocking voltage. High crystalline quality and high purity of diamond crystals are also requested in the field of research on quantum information using diamond. Although a lot of effort was devoted to improve the quality of diamond films, dislocations still remain in the crystals with the number density higher than 104 cm-2. In this study, we propose advanced diamond growth condition that removes crystalline defects effectively during the growth process of homoepitaxial diamond films.

Homoepitaxial diamond films were deposited on Ib(100) substrates using the homebuilt microwave plasma-assisted chemical-vapor-deposition (MPCVD) apparatus [1]. In this study, effect of oxygen addition during diamond growth was investigated [2]. Typical growth condition was as follows; total gas pressure, microwave power, methane concentration (flow ratio of CH4 to the total gas flow), oxygen concentration (flow ratio of O2 to the total gas flow), and substrate temperature were 120‒140 Torr, 1.2‒1.4 kW, 4‒10%, 0‒2%, and 950‒1050 °C, respectively. Microwave power density estimated from the injected microwave power divided by the plasma volume was 110‒180 W cm-3.

By optimizing growth conditions with higher oxygen concentration of 2%, high-purity homoepitaxial (100) diamond layers, typical nitrogen concentration of which was less than 1 ppb, were successfully grown. Cathodoluminescence mapping and 3D Raman measurements indicated a number density of dislocations in the homoepitaxial layer is typically 104-105 cm-2. Tungsten carbide Schottky electrodes fabricated on the non-doped diamond showed high blocking voltage of 2.2 kV. This diamond films growth technique is promising for designing high-performance quantum information devices.

The author would like to thank Dr. T. Yamamoto, Dr. S. Koizumi, Dr. K. Watanabe, Dr. H. Umezawa, Dr. S. Onoda, Dr. O. Milikofu, Prof. F. Jelezko, and Prof. J. Isoya for helpful discussion and supporting characterization.

[1] T. Teraji, T. Yamamoto, K. Watanabe, Y. Koide, J. Isoya, S. Onoda, T. Ohshima, L. J. Rogers, F. Jelezko, P. Neumann, J. Wrachtrup, and S. Koizumi, phys. stat. sol. (a) 212, 2365(2015).

[2] T. Teraji, J. Appl. Phys. 118, 115304(2015).