bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Ru-Based Binary or Ternary Thin Films By Atomic Layer Deposition for a Seedless Cu Interconnects
Authors: Kim Soo-Hyun 
Published: February 2020

Ru has been suggested as a diffusion barrier that is compatible with the direct plating of Cu. However, previous studies showed that Ru itself is not a suitable diffusion barrier for Cu metallization due mainly to its poor microstructure with polycrystalline columnar grains. This study developed several Ru-based multi-component thin films, RuMn, RuSiN, and RuAlO using atomic layer deposition (ALD) process, which are compatible with the direct plating of Cu as well as show better diffusion barrier performance against Cu than Ru. Mn, SiNx, AlOx were incorporated into the Ru by combining the Ru and corresponding ALD cycles, and Ru-based binary alloy, RuMn, ternary thin films, RuSiN and RuAlO, were fabricated at 225 oC. As a typical example, the results on ALD-RuAlO were shortly described. The step coverage of ALD-RuAlO was perfect at contact holes with an aspect ratio of ~ 25 (top-opening diameter: ~ 85 nm). XRD and TEM results indicate that ALD-Ru film prepared without AlOx ALD cycle forms a polycrystalline structure with columnar grains. But, with incorporating the AlOx cycles, RuAlO films were formed with non-columnar grains and nano-crystalline microstructure consisting of Ru nano-crystals separated by amorphous AlOx matrix. XRD analysis showed that the structure of Cu/ALD-RuAlO (8 nm)/Si was stable after annealing at 600 oC for 30 minute while Cu/Ru (15 nm)/Si structure was failed after annealing at 450 oC. It was also shown that the electroplating of Cu was directly achieved on a very thin (~8-nm-thick) RuAlO film at blanket and pattern wafer. In the case of binary ALD-RuMn film, it should be noted that after annealing ALD-RuMn film at 500 oC, the self-formation of Mn silicate barrier between Ru(Mn) film and SiO2 was confirmed based on XRD and TEM analysis, which was due to the diffusion of Mn into underlying SiO2, resulting in better diffusion barrier performance than Ru counterpart.
Acknowledgements

This work was supported by the Technology Innovation Program (Industrial Strategic technology development program, 10035430, Development of reliable fine-pitch metallization technologies) funded by the Ministry of Knowledge Economy (MKE, Korea) and also partially supported by Tanaka Precious Metals, Japan.
(Invited) Understanding and Controlling Electrochemical Effects in Wet Processing
Authors: Raghavan Srini , Chiang Chieh-Chun 
Published: February 2020

Electrochemical and redox effects permeate many aspects of wet processing in the fabrication of integrated circuits. This presentation will highlight areas where electrochemical effects are detrimental to wet processing as well as areas that can be benefited by electrochemical effects. For example, recent work has shown that megasonic cleaning of conductive surfaces can be enhanced using electrochemically generated hydrogen bubbles. Well known areas that suffer from electrochemical effects are cleaning of silicon and copper in dilute hydrofluoric acid. Challenges encountered in the processing of stack structures that have electrochemical activity will be discussed.Electrochemical and redox effects permeate many aspects of wet processing in the fabrication of integrated circuits. This presentation will highlight areas where electrochemical effects are detrimental to wet processing as well as areas that can be benefited by electrochemical effects. For example, recent work has shown that megasonic cleaning of conductive surfaces can be enhanced using electrochemically generated hydrogen bubbles. Well known areas that suffer from electrochemical effects are cleaning of silicon and copper in dilute hydrofluoric acid. After a discussion of these areas, challenges encountered in the processing of stack structures that have electrochemical activity will be discussed.
Effect of Particle Contamination on Extreme Ultraviolet (EUV) Mask and Megasonic Cleaning Process for Its Removal
Authors: Kim Min-Su , Ji Hye-Rim , Choi In-Chan , Kim Hyun-Tae , Jang Sung-Hae , Lee Jun , Kim In-Seon , Kim Jung-Hwan , Oh Hye-Keun , Ahn Jin-Ho , Park Jin-Goo 
Published: February 2020

Extreme ultraviolet lithography (EUVL) is the most promising lithography technique for the 22 nm half-pitch and beyond. The EUV patterned masks work in a reflective mode and it has 40 to 50 pairs of MoSi multilayer to reflect EUV radiation. This multilayer is capped by a 2.5 nm Ru thin film to protect the MoSi multilayer. Since EUV mask does not have a pellicle which protects mask surface from the contaminants. Therefore, EUV mask is more vulnerable to particle contamination during lithography processing which is a major yield loss in device fabrication. No study has been reported on the effect of particle size on CD variation if they exist on EUV mask. The critical defect size, which can cause 10 % CD error, has to be removed from the mask surface. When the defect is located between line and space patterns on the mask, the reflectivity will be reduced due to defect absorption. Simulation predicted that 30 nm sized silica particles can cause 10 % CD error on 16 nm line and space pattern. Thus, these contaminant particles have to be removed from EUV mask surface for preventing CD variation. In order to evaluate the 30 nm sized silica particle removal test, we adopted 30 nm standard spherical silica particles. Actually, it is a challenge to evaluate 30 nm particles removal test without inspection tools. So, we used atomic micro scope (AFM) for the evaluation of these particles. The silica particles were intentionally deposited on Ru surface using spinning method. Cleaning test was performed with twin type megasnoic. 30 nm silica particles removal efficiency was drastically decreased as compared with 137 nm silica particles at 1 MHz megasonic cleaning. Because the megasonic cleaning force was reduced to ultra-fine particles due to boundary layer thickness. Therefore, higher megasonic cleaning force is required to remove ultra-fine particles to overcome boundary layer thickness. It is well known that the large cleaning force is induced, not only particle removal efficiency but also pattern damage will be increased. Thus, megasonic cleaning process without causing pattern damage has to be optimized.
In this study, we shall discuss the effect of megasonic frequency on the removal of ultra-fine particles and pattern damage. Also, gas dissolved water and dilute alkali cleaning solution are adopted to high frequency megasonic cleaning process to achieve ultra-fine particles removal without pattern damage effectively.

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Advanced Wet-Etch-Only Process for Complete Tri-Layer Rework
Authors: Steinke Philipp , Calvo Jesús , Uhlig Benjamin 
Published: February 2020

A tri-layer patterning is used for high numerical aperture immersion lithography at 28 nm node. The tri-layer consists of a photoresist (PR) deposited on silicon containing anti-reflective coating (SiARC) above an organic planarization layer (OPL). Defective PR layer (e.g. overlay, over-exposure, residues) are repeatedly being reworked in high volume manufactories. Since selective PR removal has some disadvantages for the remaining SiARC (residues, roughness increase, thickness loss, optical properties modification) commonly, the complete tri-layer stack is removed and reprocessed. Due to the different chemical composition of the three layers, multiple etch processes (e.g. dry-wet-dry) are necessary.
In this work we investigate a wet-etch-only tri layer rework approach that takes advantage of a lower material damage, cost reduction and an increased throughput possibility. A complete removal and low defect levels on patterned 300 mm wafers have been required.
The screening of various ULSI chemicals according to their removal ability and selectivity to functional layers (TiN hardmask and TEOS cap) enabled a wet-etch-only process on an industry standard single wafer tool. Ellipsometric spectroscopy, cross-section scanning electron microscopy (X SEM), Transmission Electron Microscopy (TEM) and defect scans confirm these results.

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Post Salicidation Clean: Removal of Unreacted Pt from High Pt Content NiPt Silicide
Authors: Sehgal Akshey , Derderian Garo , Muralidhar Pranesh 
Published: February 2020

Introduction

Silicides have been used in self-aligned processes for several generations of CMOS devices, with the aim of reducing the sheet resistance and providing stable Ohmic contacts with low contact resistance on gate, source and drain areas.1 To avoid bridging at the spacers and the isolation areas, after salicide formation, unreacted NiPt needs to be removed; simplified process flow is shown in Figure 1. Theoretically, strongly oxidizing wet clean chemistries should be able to remove Ni and/or Pt in the Ni Pt salicide. Xu et al.2 used a HF and HNO3 acid mix to remove unreacted NiPt (for 5% and 10% Pt content) at high etch rates with high selectivity to other materials exposed at the wafer surface.
However, for higher Pt contents in Ni Pt salicide, the HF and HNO3 acid mix was unable to remove all the unreacted Pt (Figure 2). Other strongly oxidizing wet cleans like SPM (sulfuric peroxide mix) and aqua regia were used and found to be inconsistent; Ni Pt residues were found on the wafer surface intermittently. Therefore, we needed to find a stable high volume manufacturing (HVM) process for removing Ni high Pt residues.

Approach

The unreacted Ni high Pt residue was analyzed. Unlike previous generations of Ni-Pt, this residue was almost pure Pt. That meant that Ni was being preferentially dissolved from the Ni high Pt surface eventually resulting in a pure Pt layer. So to prevent the preferential dissolution of Ni in Ni high Pt binary alloys, wafer spin changes were used to add a physical component to the chemical dissolution. The intent was to use centrifugal force to remove the unreacted Ni Pt stringers from the wafer surface. Unfortunately, this approach did not work and pure Pt residues were still found on the wafer surface.
Extending the duration of the current wet clean steps was found to increase the attack of the NiPt salicide while the unreacted Ni Pt residue was not eliminated.
So a new wet clean chemistry was developed to completely removing all the unreacted Ni Pt consistently making the HVM ready process.

Results

Figure 3 shows the effect of using the new wet clean at the Ni Pt Strip 1 step. Complete removal of Ni high Pt residues was found. The experiment was found to be repeatable and verified on lots staggered in the production line by 2 weeks.
Additional details and results will be provided in the complete presentation.

References

[1] T. Schram et al., Microelectronic Engineering, 120 (25), pp. 157–162, (2014).
[2] K. Xu et al., ECS Transactions, 11 (2), pp. 327-334, (2007)

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(Invited) Colloidal Nanocrystal Composites with High and Low Thermal Conductivity
Authors: Wang Robert 
Published: February 2020

We present our work on thermal transport in colloidal nanocrystal composites within the context of thermoelectrics and thermal energy management. Colloidal nanocrystals consist of an inorganic crystalline core with short ligand molecules bound to the surface. These nanocrystals can be made with excellent control over size, shape, and composition, thereby enabling microstructural control over thermal energy transport.
Our first two topics focus on low thermal conductivity materials for thermoelectricity: semiconductor nanocrystal thin films and semiconductor matrix – semiconductor nanoparticle composites. Our last topic focuses on metal matrix – metal nanoparticle composites with high thermal conductivity, which can be used to thermally manage transient power spikes in high power electronics.
For the first topic, we systematically study the effect of nanocrystal diameter and surface chemistry on thermal transport in lead chalcogenide nanocrystal thin films. These samples exhibit very low thermal conductivities ranging from 0.1 to 0.5 W/m-K and we find that larger nanocrystals and shorter ligands generally lead to higher thermal conductivities. Our measurements also show that the effect of surface chemistry on thermal transport becomes more pronounced as nanocrystal diameter decreases.
For the second topic, we focus on polycrystalline In2Se3 matrices with embedded CdSe nanocrystals ranging from 0 to ~100 vol%. We find that the thermal conductivities of these composites are very low over the entire nanocrystal volume fraction range and vary from 0.3 to 0.5 W/m-K. We also find that the presence of CdSe nanocrystals strongly effects the formation of the In2Se3 matrix (i.e. grain orientation and size as well as ternary phase formation).
Lastly, we present our work on phase change Bi nanocrystals embedded in a solid Ag-matrix. The latent heat of the phase change Bi nanocrystals can absorb large quantities of transient heat generated during power spikes in power electronics operation. In addition, fast thermal energy transport is facilitated by the Ag-matrix, which leads to high composite thermal conductivities ranging from 101 to 102 W/m-K. We also use size-dependent melting of the phase change nanocrystals as a design variable for the thermal energy absorption temperature.
Ultrafine Manganese Oxide As Sodium-Ion Battery Anode Involving Charge-Transfer Between Mn(III) and Mn(II) Oxides
Authors: Weng Yu-Ting , Huang Tzu-Yang , Lim Chek-Hai , Shao Pei-Sian , Hy Sunny , Kuo Chao-Yen , Cheng Ju-Hsiang , Hwang Bing-Joe , Lee Jyh-Fu , Wu Nae-Lih 
Published: February 2020

Our investigation on manganese dioxide (MnO2) as an anode material for sodium (Na)-ion batteries (NIBs) reveals a remarkable size effect within the nanometer range on the electrochemical sodiation activity of the oxide. Space-confined ultrafine (UF)-MnO2, with an average crystal size of 4 nm, synthesized using a porous silicon dioxide templated hydrothermal process exhibits a high reversible sodiation capacity of 392 mAh g−1 compared with the negligible activity shown by the aggregates of larger (14 nm) MnO2 nanocrystallites. To our knowledge, the present study is the first to show that MnO2 is electrochemically active as an NIB anode. The UF-MnO2 anode exhibits exceptional rate and cycle performance, including a reversible sodiation capacity of >100 mAh g−1 at a current density of 7500 mA g−1 and >70% capacity retention after 500 cycles at 150 mA g−1. The enhanced cycle stability may be attributable to the solid-embedding architecture that enables the reduction of the dimensional variations in the active material. In operando synchrotron X-ray absorption near-edge structure analysis reveals combined charge–storage mechanisms involving a unique two-oxide conversion reaction between Mn(III) and Mn(II) oxides, Mn(III)–O1.5 + Na+ + e

-
« 1/2 Na2O + Mn(II)–O, and non-Mn-centered redox reactions.

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Solvothermal Route Based in Situ Carbonization to Metal-Oxide/Carbon Composite As Anode Material for Lithium Ion Battery
Authors: Chen Gen , Yan Litao , Zhou Meng , Luo Hongmei 
Published: February 2020

Magnetite (Fe3O4) is a very promising candidate as anode material in rechargeable lithium ion battery (LIBs) because of its ability to store up to eight Li per formula unit via reversible reactions, resulting in a high theoretical capacity of 924 mAh g-1. Moreover, advantages such as low cost, ease of synthesis and environmental friendliness make it a promising candidate for large scale commercial applications for LIBs. However, Fe3O4 suffers from poor conductivity, large volume change and voltage hysteresis during the electrochemical reaction, which strongly limits its practical application. For the fact that carbon in its own feature exhibits several interesting properties, including electronic conductivity, high surface area, tunable porous structure, etc., the combination of Fe3O4 nanostructures and different forms of carbon materials show promising potential in the preparation of composite anode materials.
In this work, a high pressure and temperature based solvothermal route was developed for the synthesis of Fe3O4 with carbon as a composite anode for lithium-ion batteries (LIBs). The carbon in products was a result of the in situ carbonization of organic components under high pressure (24.0 MPa) and temperature (350 °C). Composites with different amounts of carbon were prepared by annealing the solvothermal products at different temperature. Taking advantage of the high theoretical capacity of Fe3O4 and favorable characteristics of carbon, a capacity of about 610 mAh g-1 after 100 cycles was achieved for the composite with 54.6% carbon. The carbon amount depended electrochemical performance was also investigated. The Fe3O4@C composite can be used as an alternative anode material and the introduced synthetic strategy may provide further insights into the preparation of inorganic oxides coupled with carbon via in situ carbonization of organic components.

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Solvation and Desolvation Phenomenon and in-Situ NMR Studies on Stripping/Plating of Magnesium Metal in Magnesium Batteries
Authors: Wang Hao , Sa Niya , Burrell Anthony K. , Vaughey John T. , Key Baris 
Published: February 2020

Multivalent batteries are promising technologies that can potentially outperform lithium ion batteries in term of energy density, power density and unit cost.1 Among which magnesium batteries have attracted much attention over the last a few years. However, scientific challenges continue primarily due to the lack of understanding of the intercalation mechanism of multivalent ions.2 Our recent study is devoted to the understanding of the solvation and desolvation effect with 1H and 2D solid-state NMR spectroscopy by probing the movement of the water molecules and solvent molecules in the system (Bis(trifluoromethan sulfonyl)Imide dissolved in diglyme based magnesium batteries) at various charge states. It is suggested that the water and diglyme molecules play a crucial role in facilitating the intercalation of the magnesium ions in the cathode lattice upon charging and discharging. 3

In addition, the effective stripping and plating effect on the magnesium metal is also investigated. By taking advantage of in situ NMR spectroscopy, we investigate metal vs metal pseudo cells while the cells are polarized. No significant changes in the NMR spectra between the pristine and cycled pseudo cell for Grignard electrolytes, which is in agreements with reversible smooth stripping and plating.
1 D. Aurbach, Z. Lu, A. Schechter, Y. Gofer, H. Gizbar, R. Turgeman, Y. Cohen, M. Moshkovich, E. Levi, Nature
2000, 407, 724-727 10.1038/35037553.
2 H. D. Yoo, I. Shterenberg, Y. Gofer, G. Gershinsky, N. Pour, D. Aurbach, Energy & Environmental Science
2013, 6, 2265-2279 10.1039/c3ee40871j.
3 S. H. Lapidus, N. N. Rajput, X. Qu, K. W. Chapman, K. A. Persson, P. J. Chupas, Physical Chemistry Chemical Physics
2014, 16, 21941-21945 10.1039/c4cp03015j.
Direct Determination of Burgers Vectors of Threading Mixed Dislocations in 4H-SiC c-Plane Wafers Grown by PVT Method
Authors: Guo Jianqiu , Yang Yu , Wu Fangzhen , Goue Ouloide Yannick , Raghothamachar Balaji , Dudley Michael 
Published: February 2020

Threading Screw Dislocations (TSDs) have long been observed in 4H-SiC crystals grown by the Physical Vapor Transport (PVT) method. Recent studies [1] show that a significant proportion of these threading dislocations are actually mixed type dislocations with a Burgers vectors nc+ma (where n and m are integers). With the help of Synchrotron White Beam X-ray Topography, it is straightforward to distinguish these mixed type threading dislocations from pure screw dislocations simply by recording different reflections from an axially cut sample (cut parallel to growth direction) and applying the
g.b
=0and
g.bxl
=0 invisibility criteria (g – diffraction vector; b – Burgers vector). However, axial wafers are only cut from the boules slated for research purposes and are usually unavailable for boules from which commercially preferred c-plane oriented wafers are sliced. In this study, Synchrotron Monochromatic X-ray topography was carried out on a 100mm 4H-SiC c-cut commercial wafer and contrast variation was observed for each single threading screw or mixed dislocation image on six different types of 11-28 reflections. The way the contrast varied in the different reflections was also found to be different and actually depends on the nature of the dislocation itself. Ray Tracing Simulation was then carried out to confirm this observation. This simulation method is capable of simulating dislocation contrast in various geometries and it is based on the fact that orientation contrast is the predominant contributor to contrast from threading dislocations in the grazing incidence and back reflection geometries. According to the simulation results and their comparison to the observed contrast, it is in principle possible to determine the Burgers vector of any single threading dislocation using this methodology.
[1] F. Wu, H. Wang, S. Byrappa, B. Raghothamachar, M. Dudley, E. K. Sanchez, D. Hansen, R. Drachev, S. G. Mueller, and M. J. Loboda, Mater. Sci. Forum 717-720, 343(2011).
[2] X. R. Huang, M. Dudley, W. M. Vetter, W. Huang, W. Si, and C. H. Carter, Jr., J. Appl. Cryst. 32, 516 (1999).

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(Invited) Threshold Voltage Stability Comparison of Commercial SiC Mosfets and Related Issues
Authors: Green Ron , Lelis Aivars , Habersat Dan 
Published: February 2020

Silicon-Carbide (SiC) MOSFETs are beginning to gain wide acceptance for power electronics applications requiring high efficiency and high operational temperatures. There is a growing number of commercial offerings at 1200 V from different manufacturers that may have very distinctive processes that need to be evaluated in a consistent manner to make valid comparisons. As SiC MOSFET technology continues to mature, device performance and reliability should also improve. In recent years, a diverse number of publications in the literature have addressed the poor quality of the MOS gate dielectric layer, and the challenges related to charging of both interface defects and near-interfacial oxide defects during electrical and thermal stressing. A significant number of intrinsic defects in the gate oxide result from growth of the dielectric layer itself. Subsequent process steps can activate a number of these defects which can trap charge during electrical gate-stress, thereby altering the device threshold voltage. During bias temperature stressing, activation of additional oxide defects can occur, which gives rise to larger threshold voltage instabilities. The stability of the MOS threshold voltage under electrical gate-stress at high temperature is an important reliability phenomenon with potential application relevance. A large positive shift reduces on-state conduction, increases power losses, and may reduce efficiency in switch-mode converter applications. A large negative shift in the threshold voltage is a more serious reliability concern because of excessive drain leakage current in the MOS-channel during the off-state. This effect will limit blocking capability and possibly lead to device failure.
This work will provide an overview of threshold voltage stability issues in commercially-available SiC MOSFETs subject to both positive and negative gate-stress at high temperature. Figure 1 is a plot of the subthreshold-voltage shift as a function of unipolar (positive) bias stress time for commercial devices purchased between 2012 and 2015. Recent devices show significant improvement in threshold voltage shift for a +25 V gate-bias stress at 175 °C. The older commercial devices shift considerably more, with the onset of degradation occurring much earlier in time. We have also observed differences in the responses of devices from different manufactures for similar stress and test conditions. It is expected that process differences among device manufacturers would in turn, result in differences in the bias-temperature-stress responses. A fuller discussion of these test results and related issues will be presented in the final paper.

Figure 1