bluuebunny/crossref_metadata_2025 huggingface dataset:
Tesla Semi Truck - Hype or Reality: Challenges in Electrifying Light Commerical Vehicles
Authors: Sripad Shashank , Viswanathan Venkatasubramanian
Published: February 2020

While the electrification of the transportation sector is underway with a consistently increasing market share, segments like light commercial vehicles (LCVs) have not seen any significant market penetration. The major barriers are primarily in the shortcomings in specific energy, power, and cost associated with Li-ion batteries. With an initiative from several automakers to electrify other segments, there is a need to critically examine the performance requirements and to understand the factors governing such a transition in the near-term and long-term. In this study, we develop a systematic methodological framework to analyze the performance demands for electrification through an approach that couples considerations for battery chemistries, load profiles based on a set of vehicle-specific drive cycles, and finally applying these loads to a battery pack that solves a 1-D thermally coupled battery model within the AutoLion-ST framework. We evaluate four commercially available cathode chemistries, namely, LMO, LFP, NCA, and NMC, design cells for each of these systems, and characterize them on a 1-D thermally coupled battery model based on a comprehensive and experimentally validated materials database. This cell design effort is translated into a process-based and material specific battery cost model based on BatPaC, to obtain cost inputs for our framework. Using this framework, we analyze the performance of a fully electric LCV over its lifetime under various driving conditions and explore the trade-offs between battery metrics and vehicle design parameters. We find that in order to enable a driving range of over 400-miles for LCVs at a realistic battery pack weight, specific energies of about 350-400 Wh/kg or 200 Wh/kg at the pack-level needs to be achieved. A crucial factor that could bring down both the energy requirements and cost is through a vehicle re-design that lowers the drag coefficient to about 0.3. Finally, we evaluate the same trade-offs in the context of Beyond Li-ion systems like Li-S and Li-air, and observe a level off in the improvements gained with an increase in specific energy, while parameters like the pack-to-curb weight ratio (PTC) for LCVs that reflect on the overall efficiency of the vehicle are highly improved for high specific energies.

Figure Caption: Examination of future and beyond Li-ion systems for improvements in (a) Cost, (b) PTC, and (c) energy consumption for a fixed range of 200-miles and a cost of 150 $/kWh across chemistries. We see an improvement in the system level cost for an increase in pack specific energy up to 350 Wh/kg which signifies future Li-ion batteries and Li-S systems. The PTC at this specific energy is around a value of 0.15. Beyond this, the degree of improvement seen for the same increase in specific energy is reduced, since the pack weight does not remain a significant parameter for energy consumption. A similar trend is seen with the energy consumption (Wh/mile).

Figure 1
Capacity Fade Analysis and Direct, Efficient, and Real-Time Simulation of Physics-Based Battery Models for Stand-Alone PV-Battery Microgrids
Authors: Lee Seong Beom , Pathak Chintan , Ramadesigan Venkatasailanathan , Gao Wenzhong , Subramanian Venkat R.
Published: February 2020

Accurate and economical sizing of stand-alone power system components, including batteries, has been an active area of microgrid research, but current control methods do not make them economically feasible.1 Typically, batteries are treated as a black box that does not account for their internal states in current microgrid simulation and control algorithms.2 This might lead to under-utilization and over-stacking of batteries. In contrast, detailed physics-based battery models, accounting for internal states, can save a significant amount of energy and cost, utilizing batteries with maximized life and usability.

We have previously shown the implementation of the optimization and benefits of using the MPPT controller algorithm and physics-based battery model along with other microgrid components.3 In this talk, we will discuss some simple examples for microgrids as well as consider the model of battery as a pack, i.e. a set of cells in series and parallel with slight inherent variation in SoC and SoH. The results of the proposed approach are compared with the conventional control strategies and improvements in performance and speed are reported.

Acknowledgements

This work was supported by the Clean Energy Institute located in University of Washington, Seattle and Washington Research Foundation. The battery modeling work has been supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U. S. Department of Energy through the Advanced Battery Material Research (BMR) Program (Battery500 Consortium).

References

1. B. Subudhi and R. Pradhan, Sustainable Energy, IEEE transactions on,
4 (1), 89-98 (2013).

2. D. A. Beck, J. M. Carothers, V. Subramanian, and J. Pfaendtner, AIChE Journal,
62 (5), 1402-1416 (2016).

3. S. B. Lee, C. Pathak, V. Ramadesigan, W. Gao, and V. R. Subramanian, Journal of The Electrochemical Society,
164 (11), E3026-E3034 (2017).
Stablizimg Lead Cathodes for Electro-Organic Reductions
Authors: Waldvogel Siegfried R.
Published: February 2020

For the cathodic reduction of organic starting materials heavy metals, e.g. lead play an utmost role because of the high over-potential for the hydrogen evolution in protic media. Unfortunately, cathodic corrosion of lead electrodes represents a severe challenge since the product might be contaminated with the toxic heavy metal. The presentation will outline two recent strategies for stabilizing the lead cathodes: 1) leaded bronzes as powerful alternative to lead cathodes, and 2) cationic coverage of cathodes to enhance electro-reduction and avoiding cathodic corrosion. These approaches have successfully employed for the preparation of pharmaceutically relevant compounds and chemical intermediates. In addition, the scalability will be demonstrated as well.
Hydrogen Isotope Separation By Using Alkaline Fuel Cell
Authors: Ogawa Ryota , Matsushima Hisayoshi , Ueda Mikito , Dawson Richard
Published: February 2020

Introduction

The heavy hydrogen isotopes, deuterium (D) and tritium (T) are important materials in the field of nuclear energy. Particularly in recent years, development of new effective separation method is required for the water contaminated by the T. Every day the enormous volume is accumulating in Fukushima Daiichi Nuclear Power Plant. The water electrolysis, which is the industrially most general separation method, has disadvantage that consume energy is tremendous. To solve this point, we have investigated novel hydrogen isotope separation system named Combined Electrolysis Fuel Cell (CEFC) [1]. In this system, hydrogen and oxygen produced by electrolysis is used for power generation in fuel cell. From this, we can save energy and get further isotope effect by electrochemical reaction in fuel cell. Actually we reported that the D isotope was enriched in water phase by fuel cells with anion or cation conducting polymer [2, 3]. Here, we newly focused on another type of fuel cell, Alkaline Fuel Cell (AFC), and investigated the separation mechanism by several electrochemical methods.

Experimental

The anode was Ru catalyst supported by carbon and the cathode was Pt one. The electrolyte was 30 wt.% KOH solution. Pure H2­­ or D2 gas was supplied to anode and air was did to cathode. The reference electrode was Hg/HgO. Linear sweep amperometry was measured at the scan rate of 20 mA/sec until the cell voltage reached 0.4 V. Simultaneously electrochemical impedance spectroscopy (EIS) was carried out by frequency analyzer. The frequency range was from 0.1 Hz to 1 x 104 Hz. The experimental temperature was 50 ºC.

3．Results

Figure 1 shows the cell voltage-current curves of AFC. The same values of cell voltage at 0 A did not clearly demonstrate that the equilibrium potential of hydrogen oxidation reaction depended on the isotopes. The activation overvoltage, which can be detected as the voltage drop when the current was applied, was about 0.2 V for both gases. On the one hand, the cell voltage decreased linearly until the current reached 1400 mA when H2 gas was used. On the other hand, the voltage of D2 result was remarkably fallen at 1160 mA. The difference of the cell voltage was mainly attributed to the anode potential. This result suggested that the H2 gas transportation in the gas diffusion layer was faster than that of D2 probably. In the meeting, we report the separation factor of the D in a ddition to the EIS results.

[1] H. Matsushima, T. Nohira, T. Kitabata, Y. Ito, Energy. 30 (2005) 2413.

[2] S. Shibuya, H. Matsushima, M. Ueda, J. Electrochem. Soc.
163 (2016) F704

[3] R. Ogawa, H. Matsushima, M. Ueda, Electrochem. Commun.
70 (2016) 5.

Figure 1
(Invited) Capacitive Deionization of High-Salinity Water Using Ion-Exchange Membranes
Authors: Tang Kexin , Kim Yong-ha , Yiacoumi Sotira , Tsouris Costas
Published: February 2020

It is known that capacitive deionization (CDI) is not suitable for direct desalination of seawater because of its high salinity (~ 35 g L−1) and the limit in applied potential to avoid water electrolysis and oxidation of chloride ions. It has recently been reported, however, that the potential window can be expanded with the formation of an electrode-electrolyte interphase when using highly concentrated aqueous electrolyte. Studies also have proven that increasing ion concentration can greatly enhance the ion capacity of the electrodes. In addition, ion-exchange membranes (IEMs) can be used to control the electrode performance and allow application of reverse potential for electrodesorption. Here, we present the possibility to directly desalt high-salinity water and seawater through membrane CDI (MCDI). An MCDI cell was symmetrically assembled with anion and cation exchange membranes attached respectively to the anode and cathode. Our results show that the MCDI cell equipped with mesoporous carbon can remove 66.7 mg sodium chloride per gram of carbon, while the CDI cell alone (without membranes) could only remove 8.5 mg g−1 under the same conditions. Similarly, the MCDI cell equipped with carbon aerogel demonstrated a salt removal capacity of 37.3 mg g−1 in comparison with 12.9 mg g−1 of the CDI cell. These results indicate that the MCDI cell, assisted with IEMs and overpotential, can directly desalt high-salinity water regardless of the electrode material. Moreover, IEMs can prevent coion desorption at the beginning of the adsorption stage, as well as counterion adsorption at the beginning of the desorption stage, which can increase energy efficiency. For high-salinity water desalination, electrode regeneration is challenging. By applying a reversed low potential and controlling the desorption time, electrode regeneration can become effective. The presentation will include a review of CDI approaches, motivation for overpotential CDI supported by neutron imaging of electrodes and basic electrochemical experiments, characterization of electrode materials, a discussion of overpotential CDI and MCDI results including energy requirements, and a discussion of remaining challenges for direct desalting of high-salinity water via MCDI.
Sodium Titanium Phosphate As Cation Insertion Electrode for Electrochemical Separation Systems
Authors: Bootwala Yousuf , Shanbhag Sneha , Whitacre Jay , Mauter Meagan
Published: February 2020

Electrochemical separation technologies such as capacitive deionization (CDI) have evolved to be an energy-efficient desalination possible solution for treating brackish and low salinity waters.1 The achievable ion removal capacity in using capacitive carbon electrodes ranges between 0.1-0.2 mmol/g of carbon electrode.2 Further, the capacity retention of carbon electrodes is poor due to electrode ageing. In this work, we investigate the use of sodium titanium phosphate or NaTi2(PO4)3 , a Na-ion superconductor (NASICON) material as a sodium-ion selective cathode for electrochemically-driven aqueous separations. Additionally, we also discuss the importance of self-discharge or diffusive loss of sorbed ions during open circuit conditions specifically in comparing CDI system performance with that of insertion type electrodes such as NaTi2(PO4)3.

NaTi2(PO4)3, has until now only been evaluated in concentrated aqueous electrolytes and specifically for aqueous Na-ion batteries. It is however important in the context of water treatment and desalination, that we consider its performance in dilute electrolytes. NaTi2(PO4)3  shows reversible sodium-ion removal behavior over a range of sodium ion concentrations. Round trip coulombic efficiency values for these systems typically range between 40-70%, depending on the operating pH and dissolved oxygen levels in water. The causes of this efficiency loss are competing charge consumption by the hydrogen evolution reaction (HER) during the ion removal step and the chemical de-sodiation of the cathode by dissolved oxygen during ion retrieval step. 3, 4These efficiencies are improved through the use of an ion exchange resin and controlling the composition of the water near the electrode.

In addition, retained-ion loss characteristics of electrodes used for water treatment are important from the standpoint of being able to intermittently operate the electrochemical separation process. Our studies show that in even presence of dissolved oxygen, a common constituent in natural and industrial waters, the self-discharge properties of the titanium phosphate electrode are superior to porous carbon electrodes used in CDI systems. In the light of our findings, present a discussion on the utility of NaTi2(PO4)3as a insertion based electrode for sodium removal from aqueous streams.

References

1. M. A. Anderson, A. L. Cudero and J. Palma, Electrochimica Acta, 55, 3845 (2010).

2. S. Porada, R. Zhao, A. van der Wal, V. Presser and P. M. Biesheuvel, Progress in Materials Science, 58, 1388 (2013).

3. W. Wu, S. Shabhag, J. Chang, A. Rutt and J. F. Whitacre, Journal of The Electrochemical Society, 162, A803 (2015).

4. A. I. Mohamed, NaTi2(PO4)3 as an Aqueous Anode: Degradation Mechanisms and Mitigation Techniques, in Material Science and Engineering, p. 150, Carnegie Mellon University (2017).
Electro-Conversion of Renewables Originating from Waste Streams of the Pulping Process
Authors: Waldvogel Siegfried R.
Published: February 2020

The electrochemical conversion of biomass which does not compete with nutrition purposes represents an attractive field of research. In particular, waste streams that usually only employed for incineration can be used to make value-added chemicals, this approach is of interest in terms of ecological and economic aspects. In the pulping process, the major biomass by-products are lignin, tall oil, and turpentine fraction. The presentation deals with the selective electrochemical conversion of lignin to vanillin and diacids from turpentine fraction. Besides the electrochemical process, also valid work-up protocols are outlined.
Study the Mechanism of the Electrochemical Oxidation of Lignin Model Compounds
Authors: Ghahremani Raziyeh , Staser John A
Published: February 2020

Lignin has a high potential to be a renewable source of aromatic compounds due to its polyphenolic structure. Electrochemical oxidation of lignin on nickel–cobalt electrodes introduced an environmentally friendly, and economic procedure to convert lignin to other value-added aromatic compounds. However, lack of knowledge about the mechanism of the lignin electrochemical oxidation process, because of the complexity of the molecule, makes the conversion process more elaborate and complex. Understanding the mechanism of the lignin model compounds, which represent building blocks and linkages of lignin molecule, contributes controlling the lignin depolymerization process. Electrochemical study allows us to understand the reaction pathway, and demonstrate the mechanism by the aid of cyclic voltammetry. In this work we have presented the electrochemical oxidation mechanism of the lignin model compounds in the typical three electrode cell beaker using a Pt rotating disc electrode (RDE) as the working electrode. The effects of the concentration of the compounds, supporting electrolyte pH, and working electrode rotation rate have been also studied through cyclic voltammetry experiments.
Mechanistic Insights into Furfural Reduction on Metal Electrodes: Distinguishing Pathways for Selective Hydrogenation of Biorenewable Oxygenates
Authors: Chadderdon Xiaotong , Chadderdon David J , Matthiesen John Edward , Tessonnier Jean-Philippe , Li Wenzhen
Published: February 2020

Electrochemical reduction of biorenewable platform chemicals is an emerging route for sustainable biofuel and chemicals production [1-3]. However understanding gaps between reaction conditions, underlying mechanisms, and observed product selectivity have limited the rational design of effective, active, and stable electrochemical systems. In this presentation, the mechanisms of electrochemical reduction of furfural, an important biobased platform molecule and model for aldehyde reduction are explored through a combination of voltammetry, bulk electrolysis, thiol-electrode modifications, and kinetic isotope studies. It is demonstrated that two distinct mechanisms are operable on metallic Cu electrodes in acidic electrolytes and lead to different products: (i) electrocatalytic hydrogenation (ECH) for methyl furan (MF) and furfuryl alcohol (FA) production, and (ii) direct electroreduction for dimers production. The contributions of each mechanism to the observed product distribution is clarified by evaluating the requirement for direct chemical interactions with the electrode surface and the role of adsorbed hydrogen. Further analysis reveals that hydrogenation and hydrogenolysis products are generated by parallel ECH pathways. Understanding the underlying mechanisms enables the manipulation of furfural reduction by rationally tuning the electrode potential, electrolyte pH, and furfural concentration to promote selective formation of important biobased polymer precursors and fuels.

References:

1. Xin, L. et al., ChemSusChem
2013, 6, 674–686.

2. Matthiesen, J. E. et al. ACS Sustainable Chem. Eng.
2016, 4, 7098–7109.

3. Suástegui, M.; Matthiesen, J. E.; et al. Angew. Chem. Int. Ed.
2016, 55, 2368–2373.
Surface Treatment Method and Its Metrology for Preventing Pattern Collapse
Authors: Bai Chuannan , Wang Jingjing , Shalyt Eugene
Published: February 2020

As semiconductor industry continues to make patterns smaller and more sophisticated, stable patterns with high AR (aspect ratio) is required. Pattern collapse is often affected by the AR, rigidity of pattern material, and surface chemistry of the sidewalls. Historically, hot IPA treatment was used but it does not support latest generation devices. One of the novel effective pattern collapse prevention approaches is the surface treatment with an organic layer [1, 2]. The modified structure surface has lower surface tension and the capillary force is reduced. This treatment process is normally performed by a silane-coupling reaction using organic solvent, so that the hydrophilic surface (-Si-OH) is modified to hydrophobic (-Si-O-SiR3) after silylation reaction. Silyning agent has limited stability and decompose upon exposure to air, moisture or reactive surfaces. Thus, there is a need the tight process control. A variety of spectroscopic methods were studied in order to measure selectively the active silyning agent and breakdown byproducts. Presentation will summarize advantages and disadvantages of different approached, preferred process control strategy and test results for non-reagent, real time analyzer of STM chemistry. TOKYO OHKA KOGYO CO., LTD. (TOK) is highly acknowledged for providing test samples and technical discussions.

[1] D. Mori et al. Surface treatment agent and surface treatment method United States Patent Application 15/268,904

[2] E. Kesters et al. Wet clean challenges in 22nm ½ pitch and 16nm ½ pitch Proceedings of SPCC conference 2017

Figure 1
Post Cleaning for FEOL CMP with Silica and Ceria Slurries
Authors: Tseng Wei-Tsu , Jha Amarnath , Stoll Derek , Wu Changhong , McCormack Tim , Yang JI Chul
Published: February 2020

For the manufacturing of Si-based semiconductors, CMP is utilized extensively to enable FEOL process integration such as STI, deep-trench, ILD, and poly-open. Silica slurries are usually adopted for bulk oxide polish while ceria slurries are more suited for the final “buff” polish where high selectivity to nitride is required. The ever stringent requirement for scratch reduction leads to the trend of using nano-sized abrasive particles in all types of CMP slurries. However, the stronger adhesion force between these nanoparticles and wafer surface necessitates the re-design and optimization of post-CMP processes to meet the low PR/FM defect requirement.

The selection of proper chemicals is often the first step towards post-CMP cleaning. However, design of cleaning sequence, exploitation of the tool hardware, and optimization of operating parameters are equally critical to achieve maximum cleaning efficiency. As shown in Fig. 1, for an oxide or poly-Si CMP process with an acidic silica-based slurry, a preferred post cleaning process should operate in alkaline environment (e.g., pH 8~10) in order to build in repulsive zeta potential for easy of particle removal from wafer surface.

In this case, the use of an acidic pCMP chemical would be unfavorable from zeta-potential point of view. Replacement of acidic chemical with just DIW (pH ~ 7) leads to significant reduction in PR/FM. In addition, optimization of the directionality, spin rpm, arm oscillation speed…etc, helps eliminate the wafer center-heavy signature and reduces the defect count further down.

For FEOL CMP with ceria-based slurry running on a 3-platen polisher with serial meg tank/brush cleaning module, one can design the pCMP process based on the unique “reactive” nature of ceria abrasives, and also fully exploit the available hardwares and their process parameters. In this example, the POR process adopts only DIW in the meg tank. The go-to process, however, replaces DIW with a diluted acidic oxidizer so as to neutralize the reactive ceria abrasives, making it much easier to dislodge the particles from oxide wafer surface.

The significant FM NADD reduction with the go-to pCMP process illustrates the efficiency of adding the meg clean step with diluted oxidizer. Further PR/FM reduction can be realized by optimizing the hardware and machine parameters such as those listed in Fig. 2, from on-platen buff clean all the way to the terminal step of Maragoni drying. Furthermore, for a new pCMP process to be considered production-ready, run order effects, repeatability, and CoO reduction need to be taken into account as well. In addition, post-clean surface analyses are carried out to ensure no potential reliability concern.

Reference:

W.-T. Tseng, J. Hagan, K. Mohan, R. Hull, J. MacDougall, R. Murphy, L. Tai, S. Molis, “Post Cleaning and Defect Reduction for Tungsten Chemical Mechanical Planarization” ICPT, 2015.

Figure 1
A Novel Cleaning Approach to Remove the Carbon Contaminant from Ru Surface of EUV Mask
Authors: Kim Min-Su , Song Hee-Jin , Kim Hyun-Tae , Park Jin-Goo
Published: February 2020

The surfaces of extreme ultraviolet (EUV) mask and optics are very vulnerable to carbon contamination during EUV lithography process. The top surface of EUV mask is coated with Ru capping layer to protect the mask substrate. Carbon contamination occurs on Ru surface when the EUV light of 13.5 nm interacts with the surface. The carbon contamination on mask surface is known to lose its reflectivity and change the critical dimension (CD). Thus, the removal of carbon contaminant from mask surface is required to maintain the integrity of EUV lithography process. Conventional cleaning methods such as SPM and UV cleaning are widely used for the removal of organic contaminants but can cause surface damages on EUV mask such as surface oxidation and etching of absorber pattern.  

In this study, a novel cleaning mechanism is proposed to remove carbon contaminant using a quaternary ammonium hydroxide solution and an organic solvent mixture solution. According to the SN2 (nucleophilic substitution) reaction, hydroxyl ions are ready to react with carbon atoms as nucleophiles. Also, polar aprotic solvents such as DMSO solvate cations to actively assist hydroxyl ion reactions. Therefore, a study on the removal of carbon contaminants was carried out using a mixture of quaternary ammonium hydroxide solution and polar aprotic solvent. There have been limited studies reported on organic solvent cleaning in a semiconductor process for removal of photoresist. However, physical cleaning such as megasonic and UV treatment were applied to the organic solvent cleaning process to improve organic removal. Few studies have also been carried out to remove the photoresist by applying an additional cleaning process such as CO2 aerosol, megasonic, and UV pretreatment to the organic solvent. So far no studies have been reported on the removal of carbon contaminants using quaternary ammonium hydroxide solution with an organic solvent. This study investigated the effect of cleaning solution on hydrocarbon film removal by using four kinds of quaternary ammonium hydroxide (TMAH, TEAH, TPAH and TBAH) as alkaline chemicals and DMSO and THF organic solvents as polar aprotic solvents. Instead of EUV carbon contaminant, a hydrocarbon film with similar properties to EUV carbon contaminant was prepared and evaluated using alkaline chemicals and organic solvents. The hydrocarbon film was effectively removed from Ru surface in the mixture of TBAH and THF. This is because of low polarity nature of both TBAH and THF. When DMSO used with quaternary ammonium hydroxide solution, hydrocarbon was also removed with longer process time. The carbon removal efficiency is improved and reduced the cleaning process time for TBAH+DMSO cleaning process with megasonic due to the easy lift-off of hydrocarbon film from Ru surface. The polarity of carbon contaminant and cleaning solution have to be considered for removal carbon contaminant from Ru surface.
Study of SiGe Surface Cleaning
Authors: Komori Kana , Wostyn Kurt , Rondas Dirk , Prado Jana Loya , Conard Thierry , Loo Roger , Ragnarsson Lars-Åke , Horiguchi Naoto , Holsteyns Frank
Published: February 2020

Recently Si can be replaced with SiGe in FinFETs (field-effect transistors) and GAA (gate all around) structures in order to get the higher carrier mobility. However, Ge oxide concentration of SiGe oxide causes an increase in interface trap density (Dit) and becomes a defect of device. Although Si and Ge surface treatments have been studied so far, SiGe surface treatment is still not well understood. Recently cleaning of SiGe surface is required and began to be studied for Ge concentration of SiGe oxide by dry and wet cleaning has been reported [1-2].

For cleaning of SiGe surface, this study focused on wet process solutions of O3 water and acids (HF and HCl) with Si1-xGex (X=25-45%) wafer. The behavior of oxide is shown by using these chemical solutions individually or in combination. XPS measurement showed differences of Ge oxide concentration.

As first experiment, native oxide shows Ge concentration of oxide and substrate are same or slightly less than substrate. On the other hand, chemical oxide by using O3 water showed concentration of Ge oxide is 10% less than substrate on Si75Ge25 wafer.

This study shows the behavior of SiGe surface can be controlled by changing chemical concentration or chemical combination. Details of results will be reported in presentation.

[1]S.L.Heslop,et al.,in:ECS Transactions,69 (8) 287-293 (2015)

[2]Sang Wook Park,et al., in:J.Vac.Sci.Technol.A,Vol.33,No.4,Jul/Aug 2015
Nearly Anhydrous Undissociated HF for the Removal of Hf / Ta / Zr Based Polymers after Plasma Etch, Selectively to Aluminum
Authors: Cazes Marine , Broussous Lucile , Garnier Philippe , Pizzetti Christian , Gabette Laurence , Besson Pascal
Published: February 2020

The removal of tough Ta, Zr or Hf based polymers selectively to aluminum is a challenging concern in the fabrication of High-K capacitors or specific metals stacks with thick Tantalum layers for example (fig.1, 2 ). Most of actual commercial chemistries only barely touch some of the toughest polymers generated by plasma etch process as seen in Fig 3. HF is sometimes employed but has shown moderate efficiency (fig 4,5) associated with a serious risk of metals and oxide consumption if not well controlled for some critical structures.

HF is commonly used to pattern amorphous or damaged HfO2 highK gates, and the selectivity to thermal silicon oxide has been studied in details by V. Paraschiv [2] showing the relative importance of each species in the etching mechanism. Moreover, in early studies around the use of HF for silicon dioxide etching, the need and the role of condensed water or alcohol together with HF vapor is well documented.[1, 3], and the detailed mechanism involved in the silicon dioxide dissolution in diluted HF is widely accepted [4]. Finally the hydration of hydrogen fluoride is not as rapid and straightforward as other halides like chlorine and Bromine [5] therefore at low water content hydrogen fluoride can be seen as nearly anhydrous solution.

This paper describes the work that has been done in collaboration with STMicroelectronics to evaluate a newly released chemistry IK 73 from TECHNIC France which combines the advantages of being nearly anhydrous and avoids the HF dissociation at any dilution ratio with water (see graph 1), for the removal of Ta, Hf and Zr based polymers after dry etch and ash, selectively to Aluminum eventually exposed.

The main features of the chemistry and its behavior on blanket films at different dilutions ratios will be first exposed. Morphological results (SEM-TEM) on various kinds of structures are presented, as illustrated in fig.6,7.

From the results obtained we conclude that it is possible to efficiently dissolve Ta, Zr, Hf based polymers (or their amorphous oxides) selectively to aluminum, thanks to TechniClean IK 73.

Reference

[1] Won Ick Jang, Chang Auck Choi, Myung Lae Lee, Chi Hoon Jun and Youn Tae Kim .
J. Micromech. Microeng. 12 (2002) 297–306

[2] V. Paraschiv, M. Claes, M. R. Baklanov, W. Boullart, S. De Gendt, S. Vanhaelemeersch, Solid State Phenomena Vols. 103-104 (2005) pp 97-102

[3] Ron Hanestad ; Jeffery W. Butterbaugh ; Abdselem ben-Hamida ; Ilaria Gelmi Proc. SPIE 4557, Micromachining and Microfabrication Process Technology VII, 58 (September 28, 2001); doi:10.1117/12.442986

[4] D. Martin Knotter J. Am. Chem. Soc., 2000, 122 (18), pp 4345–4351

[5] Odde S, Mhin BJ, Lee KH, Lee HM, Tarakeshwar P, Kim KS

T
he Journal of Physical Chemistry A 110(25):7918-24 · July 2006

Figure 1
(Invited) Thermal Cyclic Atomic-Level Etching of Nitride Films: A Novel Way for Atomic-Scale Nanofabrication
Authors: Shinoda Kazunori , Miyoshi Nobuya , Kobayashi Hiroyuki , Kurihara Masaru , Izawa Masaru , Ishikawa Kenji , Hori Masaru
Published: February 2020

Because the structure of semiconductor devices has changed to miniaturized three-dimensional (3D) structures, etching technologies that enable 3D atomic-scale control have received increasing interest. Therefore, atomic level/layer etching (ALEt), which is a counterpart of atomic layer deposition (ALD), has attracted much attention due to its potential in atomic-scale 3D nanofabrication. ALEt typically involves a cyclic repetition of self-limiting formation and desorption of surface modified layers. Thus, geometric loading effects are mitigated when using ALEt because of the self-limiting behavior.

The authors have developed a novel isotropic ALEt process for SiN using cyclic repetitions of hydrofluorocarbon-based plasma exposure and thermal annealing [1]. The first step of the etching cycle for SiN is exposing the sample surface at room temperature to hydrofluorocarbon-based radicals that form ammonium hexafluorosilicate ((NH4)2SiF6) on SiN. The second step is thermal annealing above 100°C to sublimate the ammonium hexafluorosilicate. SiN film with an atomically thin layer can be etched away by repeating the cycle of forming and by removing the ammonium hexafluorosilicate. This cyclic etching shows self-limiting behavior because the formation of the ammonium hexafluorosilicate saturates as the plasma exposure time increases. This technology is applicable to other nitride films besides SiN. The authors have demonstrated selective isotropic ALEt of TiN [2], which is widely used as a gate electrode and barrier metal in semiconductor devices.

In this paper, we present our results with the isotropic ALEt process for SiN and TiN. This method features a variety of promising characteristics, such as high selectivity with respect to SiO2and poly Si, atomic-level control of the etching amount, and isotropic etched profiles. The authors developed a novel etching apparatus as an ALEt tool for 300-mm wafers. This apparatus utilizes an infrared (IR) lamp for thermal annealing to achieve rapid temperature cycles. Particular attention is devoted to the surface reaction mechanism in the novel isotropic ALEt process for SiN. The results of in situ X-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS) are described; they reveal the formation and decomposition of ammonium hexafluorosilicate on SiN during the cycle of plasma exposure and annealing. The potential industrial applications of these two processes are also described.

[1] K. Shinoda et al., Appl. Phys. Express 9, 106201 (2016).

[2] K. Shinoda et al., AVS Symposium and Exhibition, PS+TF-WeM10 (2016).
(Invited) Research to Manufacturing: ALD Design for Precision Atomic Layer Fabrication
Authors: LaVoie Adrien R. , Kumar Purushottam
Published: February 2020

Novel atomic layer engineering technologies have emerged as key developmental tools for <2X node fabrication in the modern semiconductor manufacturing. Today’s applications include front-end-of-line (FEOL) spacers and liners, isolation gapfill, FinFET conformal doping, multi-patterning layers, through-silicon via liners, sacrificial layers, encapsulation, selective deposition/etch, conformal etch, and surface smoothening to name a few.

In the first section, industrial drivers including intelligent devices, economics, and inflection points will be correlated to atomic layer engineering market applications. The advantageous qualities of self-limiting and saturation technologies will be reviewed with a focus on implications for throughput, unit film property optimization, and controlling process variation. An alternative paradigm shift for processing in the “sub-saturated regime” will be reviewed with attention to the pros and cons. The complementary nature of ALD and ALE will be considered with a predictive look at the future of atomic layer engineering.
ALD of Fluorine-Free Boron-Containing Composite Layers for Shallow Dopant Source Applications
Authors: Mane Anil U. , Liu Jian , Farha Omar , Letourneau Steven , Pupek Krzysztof Z. , Hupp Joseph T. , Elam Jeffrey W
Published: February 2020

Conformal coating of boron-containing films via atomic layer deposition (ALD) could be used as a shallow dopant source for advanced 3D-transistor structures in VLSI manufacturing. Aiming this application, fluorine (F) -free precursors of boron such as boric acid (B(OH)3) and trimethyl borate (B(OCH3)3) were explored as ALD precursors in a combination with Al2O3 ALD process. The ALD of Al2O3 was performed using trimethyl aluminum (Al(CH3)3) and Deionized H2O. The complex chemistry resulted in deposition of boron containing composite films of (BxAl2-xO3). In-situ quartz crystal microbalance study was performed to evaluate the optimum ALD precursors dose times as well as confirms the self-limiting behavior of the ALD processes. Growth rate of composite BxAl2-xO3 processes under various ALD conditions are in the range of 0.8-1.1Å. The resultant boron containing BxAl2-xO3 films was analyzed for composition by x-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), ellipsometry, and electrical capacitance measurements. Atomic composition of B was tailored by adjusting relative ratio of the B to Al precursors cycle during ALD process. A rapid thermal annealing was performed as a function of time and temperature and confirms B-diffusion in the Si(wafer) as well as changes in optical properties of the BxAl2-xO3 layers. Here we will present detailed investigation of ALD grown BxAl2-xO3 layers.
Atomic Layer Deposition Lithium Fluoride As Coatings for Lithium-Ion Batteries
Authors: Chen Lin , Elam Jeffrey W , Libera Joseph A.
Published: February 2020

In this work, atomic layer deposition of lithium fluoride has been studied with in-situ quartz crystal microbalance (QCM), quadrupole mass spectrometer (QMS), and Fourier transform infrared (FTIR) spectroscopy. The LiF ALD film growth was examined at temperatures from 150 to 350 °C. The presursors used in this study reveal self-limiting behaviors. Film thicknesses on silicon substrates were also determined using ex-situ X-ray reflectivity (XRR) and spectroscopic ellipsometry (SE) measurements. Grazing incidence X-ray diffraction (GIXRD) and XRD for thick films both indicate that the ALD LiF as-deposited at 150 °C is crystalline. X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectrometry (RBS) measurements demonstrate that the deposited films were nearly stoichiometric LiF with very small amount of hydrogen impurity. The electrochemical meausrements of the ALD LiF coating on both cathodes and anodes for lithium-ion batteries will be presented.
Digital Doping of ALD VO2 for Thermochromic Applications
Authors: Kozen Alexander C , Currie Marc , Jungjohann Katherine L , Downey Brian P. , Eddy Charles R , Wheeler Virginia D.
Published: February 2020

Vanadium Dioxide (VO2) is an interesting thermochromic material that undergoes a first order crystalline phase transition at a critical temperature (Tc) of 68˚C. This structural phase transition is accompanied by major changes in electrical and optical properties, particularly in the infrared. As such, VO2 is suitable for many applications including microbolometers, adaptive thermal coatings, and passive spacecraft thermal shielding.

While the Tc of VO2 is convenient for many applications, it is desirable to modify the Tc to other values for either new applications or improved performance in the previously stated applications. The Tc of VO2 is known to be strain-mediated.[1] Strain in VO2 has been induced via deposition of thin films onto lattice mismatched epitaxial substrates, as well as by doping with other transition metal elements besides vandium.[2], [3]

For the first time, we are investigating digital doping of ALD VO2 using other elements such as Al, Ti, Nb, and W by incorporation of their oxides into the binary ALD VO2 process (TEMAV + O3). We will discuss the fundamentals and limitations of doped ALD VO2 growth and basic materials characterization, and will demonstrate the impact of dopant concentration and identity on the optical and electrical phase transition properties of the resulting films.

Generally, inclusion of dopants such as Ti and Al into the ALD VO2 process in amounts between 1% and 10% results in surfactant-like film growth behavior, with increasing dopant concentrations reducing RMS roughness of the ALD films from ~2 nm to ~0.2 nm. Higher concentrations of dopants also interfere with film crystallization during annealing, inhibiting the magnitude of the metal-insulator transition. Smaller concentrations of dopants, between 1% and 3%, can lower the Tc of the VO2 films while maintaining acceptable optical behavior, depending on dopant identity and concentration. In particular, we find that Nb doping at these low concentrations decreases Tc of VO2 by -13.5˚C/Nb%.

[1] J. M. Atkin, S. Berweger, E. K. Chavez, M. B. Raschke, J. Cao, W. Fan, and J. Wu, “Strain and temperature dependence of the insulating phases of VO 2near the metal-insulator transition,” Phys. Rev. B, vol. 85, no. 2, pp. 020101–4, Jan. 2012.

[2] W. Burkhardt, T. Christmann, B. K. Meyer, and W. Niessner, “W-and F-doped VO 2 films studied by photoelectron spectrometry,” Thin Solid Films, vol. 345, no. 2, pp. 229–235, 1999.

[3] X. Wu, Z. Wu, C. Ji, H. Zhang, Y. Su, Z. Huang, J. Gou, X. Wei, J. Wang, and Y. Jiang, “THz Transmittance and Electrical Properties Tuning across IMT in Vanadium Dioxide Films by Al Doping,” ACS Appl. Mater. Interfaces, vol. 8, no. 18, pp. 11842–11850, May 2016.
Reusable Sorbent for Oil Spill Cleanup Fabricated Using Sequential Infiltration Synthesis
Authors: Elam Jeffrey W , Avila Jason R , Barry Edward F. , Darling Seth B. , Libera Joseph A. , Mane Anil U.
Published: February 2020

Crude oil spills in the ocean can be devastating to the environment and extremely expensive to mitigate. Furthermore, while oil on the surface can be removed by skimming or burning, there are currently no technologies for the cleanup of subsurface oil droplets in the ocean. To address this need, we have developed a reusable sorbent material, OleoSponge. To synthesize this material, we begin with commercial polyurethane foam, and first treat the foam using sequential infiltration synthesis (SIS). SIS is similar to ALD in that it uses alternating, self-limiting exposures between gaseous precursors and a substrate. However, whereas the ALD substrate is a solid surface, in SIS the substrate is a polymer, and the precursors react on organic functional groups within the polymer to seed the nucleation of metal oxide clusters. We performed in situ infrared spectroscopy and mass spectrometry to elucidate the mechanism for metal oxide SIS within the polyurethane foam, and we have studied the effects of temperature, time, and partial pressure on the resulting SIS deposits. The next step is to graft an oleophilic monolayer onto the SIS-treated foam, either through gas-phase or solution phase treatment. The resulting material is simultaneously hydrophobic and oleophilic, and is able to rapidly extract oil from water. We have performed extensive bench-scale testing using 1” cubes of the OleoSponge and found that it absorbs >40x its weight in oil, and can be simply squeezed out and used again. Next, we performed a 10,000 scale up, and tested the material at the Ohmsett facility in Leonardo, New Jersey, using the largest outdoor saltwater tank facility in North America. The OleoSponge performed very well in extracting subsurface crude oil and diesel fuel from seawater under realistic conditions.
(Keynote) Interface Control for High Performance N-Channel Ge FETs
Authors: Toriumi Akira
Published: February 2020

The demonstration of high electron mobility Ge n-MOSFETs was not an easy task. To overcome such big challenge, three carrier scattering mechanisms in Ge MOS inversion layer such as Coulomb scattering, phonon scattering, and surface roughness scattering were carefully investigated. The first step was to improve the peak electron mobility by reducing the interface states density (Dit
). We succeeded in the reduction of Dit
(<1011 eV-1cm-2) at Ge/GeO2 interface by employing the high-pressure O2 (HPO) oxidation [1]. This is quite reasonable thermodynamically [2]. However, there still remained two critical challenges. One was how to suppress the significant degradation of high-Ns electron mobility. The other one was how to keep electron mobility high in thin EOT region [3].

It is generally considered that high-Ns electron mobility is dominated by the interface roughness scattering. Since we demonstrated that Ge(111) was the best surface orientation for electrons to achieve the highest peak electron mobility, we challenged to realize the atomically flat Ge(111) surface by using H2 annealing [4]. Then, MOSFETs on Ge(111) with and without atomically flat surface were fabricated with HPO. N-channel MOSFETs fabricated by HPO on atomically flat Ge(111) exhibited greatly improved high-Ns electron mobility [5].

EOT reduction was also challenging because HPO should naturally form thicker GeO2. This fact was a big hurdle on Ge FET technology. Meanwhile, it was interestingly found that the low-temperature HPO (LT-HPO) reduced the oxidation rate [6]. This fact enabled us to achieve ~2 nm EOT GeO2 on Ge with superior interface and bulk GeO2. Another way to reduce EOT is obviously to replace HPO-GeO2 with other high-k oxides which are appropriate for Ge. We have fortunately found that Y2O3 is very friendly with Ge [7]. Furthermore, in our recent experiments Y2O3-doped GeO2 (YGO) is much better than pure Y2O3 on Ge. Significantly improved electron mobility in n-channel Ge FETs in a wide range of electron density has been achieved, when YGO in addition to H2 annealing has been used for the interfacial layer in gate stacks [8].

Poor electron mobility in n-channel Ge FETs is not true now. We can engineer the Ge interface through understanding of thermodynamics in gate stack formation and of kinetics of both surface planarization and oxidation. Thus, we can safely conclude that Ge is very promising not only for p-channel but also for n-channel FETs.

References

[1] C. H. Lee et al., TED 58 (2011)1295.

[2] K. Nagashio et al., MRS Symp. Proc. 1155 (2009) C06-02.

[3] M. Caymax et al., IEDM 2009-461.

[4] T. Nishimura et al., APEX 5 (2012)121301.

[5] C. H. Lee et al., IEDM 2013-32.

[6] C. H. Lee et al., APEX 5 (2012)114001.

[7]A. Toriumi et al., “Advanced Gate Stacks for High-Mobility Semiconductors", Chap. 11, (Springer, Berlin, 2007).

[8] C. H. Lee et al., IEDM 2013-40.
Three-Layered Stacking Process by Au/SiO2 Hybrid Bonding for 3D Structured Image Sensors
Authors: Honda Yuki , Goto Masahide , Watabe Toshihisa , Hagiwara Kei , Nanba Masakazu , Iguchi Yoshinori , Saraya Takuya , Kobayashi Masaharu , Higurashi Eiji , Toshiyoshi Hiroshi , Hiramoto Toshiro
Published: February 2020

A 3D structured CMOS image sensor is investigated wherein two layers (photodiode array layer and signal processing circuit layer) are stacked using a low-temperature Au/SiO2 hybrid bonding technique [1]. We previously reduced the pitch of Au electrodes from 40 μm to 6 μm and confirmed that the Au electrodes could be electrically interconnected via the bonding technique [2]. To further enhance its performance, higher integration by multilayer stacking is essential. Therefore, we developed a multilayering technique by direct bonding and manufactured a three-layered daisy-chain test device to examine the numerous interconnections.

The device is fabricated by the process described in Fig. 1 using the following steps: (a) an aluminum wiring layer is formed in a SiO2 dielectric layer on a Si substrate; (b) first via holes are formed on the surface of the SiO2 layer and are embedded with electroplated Au; (c) an Au/SiO2 bonding surface is formed by chemical–mechanical polishing (CMP), and the wafer is diced into the top-, middle-, and base-layer chips; (d) the bonding surfaces of the top- and middle-layer chips are activated by O2 plasma; (e) the top- and middle-layer chips are directly bonded by applying a force of 20,000 N for 60 min at 330 °C; (f) the Si substrate of the middle-layer chip is removed by grinding and XeF2 vapor-phase etching; (g) second via holes are formed on the exposed backside of SiO2 of the middle-layer chip and are embedded with an electroplated Au; (h) an Au/SiO2 bonding surface is formed on the backside of the middle-layer chip by CMP; (i) the bonding surfaces of the middle- (backside) and base-layer chips are activated by O2 plasma; and (j) the bonded (top- and middle-layer) chip and the base-layer chip are directly bonded by applying a force of 20,000 N for 60 min at 330 °C. Figure 2 shows a cross-sectional scanning electron microscopy (SEM) image of the three-layered daisy-chain test device. No voids were observed at the two bonded interfaces. Details of the three-layered stacking process and experimental results will be discussed in the presentation.

1. M. Goto et al., IEEE Trans. Electron Devices, vol. 62, no. 11, pp. 3530–3535, (2015).

2. Y. Honda et al., ECS Trans., vol. 75, no. 9, pp. 103–106, (2016).

Figure 1