bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Investigation on Atomic Migration Effect on Thermal Conductivity of Al/Cu Interface Structures in Electronic Interconnection Packaging
Authors: Zhang Liqiang , Ge Daohan 
Published: February 2020

At present, MEMS and micro/nano electronic packaging technology have an exhaustive range of applications in the field of mass-produced commercial products, such as cell phones, computer, automobiles, and pedometers, which cause a strong demand for the reliability of heat transfer in nano or micro scales. Wire bonding process has been widely used in the MEMS or devices packaging approach to create high aspect interconnection structures [1], hence, the thermal analysis, thermal design, and thermal management become more and more important for microelectronic system or microelectronic devices. The interfacial structures of dissimilar materials are suffering the high stress gradients due to the thermal and stiffness mismatches of the different materials [2, 3]. The interface structures of dissimilar materials are very prone to crack initiations under the heat flow effect. The heat transfer across the interface is a critical consideration for the thermal design in the IC or devices manufacturing.
Here we reveal the relationship between the atomic migration and thermal conductivity of Al/Cu interface in nanoscale heat transfer by using non-equilibrium molecular dynamics method.
To create the Al/Cu interface, the modified Embedded-atom method (EAM) for alloy is used to describe the interatomic interactions between Cu/Cu, and Al/Cu interface.
The results show that the interfacial diffusion is enhanced with the increase of the temperature from 400K-600K. The thermal conductivity of the Al/Cu interface, first increases, and then decreases. When the temperature is over 600K, it reaches the recrystallization temperature of Al. which makes to Al atoms recrystallization. The recrystallization of Al atoms may reduce the heat transfer efficiency of the Al/Cu diffusion region. That is to say, it reduces the thermal conductivity of Al/Cu interface when the temperature is over 600K. This means that we can enhance the interfacial heat transfer efficiency of Al/Cu interface and the cooling efficiency of IC by heat treatment in advance on interface structures. This investigation is helpful for understanding the interfacial heat transfer mechanism of the interface structures in the IC, which is helpful for the design of the interface in micro/nano manufacturing and benefit for the estimate the reliability of the IC manufacturing.

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(Invited) Non-Volatile Resistive Memory: Technology Capable of Revolutionary Compromises
Authors: Navarro Gabriele , Vianello Elisa , Sousa Véronique , Molas Gabriel , Nowak Etienne , De Salvo Barbara , Perniola Luca 
Published: February 2020

LETI, a French research center, has developed during the past 20 years a strong expertise on Non-Volatile Memory Devices, covering Flash evolutive solutions (Si-Ncs, TANOS, FinFLASH, 3D, Splitgate) and disruptive technologies (Phase-Change PCM, Oxide-based RAM OxRAM, Conductive-Bridge RAM CBRAM, Magnetic STT-MRAM). Main LETI expertise concerns material science, memory module integration, physico-chemical analyses, device electrical characterization, physical modeling and simulation up to circuit design, to exploit at best the memory performances of each of the aforementioned technologies.
Few key examples in the domain of the OxRAM, CBRAM and PCRAM will be provided in order to target the high temperature data retention specifications of emebedded memory market.
Some tradeoffs appears in each of the aforementioned technologies, like stability against temperature stress versus crystallization speed in PCRAM; or stability against temperature versus forming or programming voltages in CBRAM (in particular chalcogenide based CBRAM with respect to oxide based CBRAM).
In order to develop an optimized memory stack and accelerate the adoption of these new technologies, LETI offers a so-called Memory Advanced Demonstrator (MAD) that is today based on 130 nm ground rules with 4 copper metal lines. The memory module that can consist of PCM, or OxRAM, or CBRAM or MRAM technology is fabricated in the BEOL before pad level. This versatile test vehicle offers the possibility to have on the same silicon test structures spanning from simple resistors (1R), resistors with its selector transistor (1T1R), memory arrays (1kb cuts) up to complex designs allowed by the routing placed on the 4 metal levels. Such complex design may come from client designers using DK plus memory add-on provided by LETI.
All such structures are essential for a deep analysis of the memory functionality: from bulk material (with its interfaces) screening, obtained by the 1R and 1T1R; passing through statistical analysis of extrinsic bits, obtained by memory arrays; up to first validation of complex functions obtained by specific designs.
MAD offers also a benchmark opportunity between different technologies with the same test vehicle in order to extract benefits and drawback from each of them.
(Invited) Floating Gate Type SOI-FinFET Flash Memories with Different Channel Shapes and Interpoly Dielectric Materials
Authors: Liu Yongxun , Nabatame Toshihide , Matsukawa Takashi , Endo Kazuhiko , O'uchi Shinichi , Mizubayashi Wataru , Morita Yukinori , Migita Shinji , Ota Hiroyuki , Chikyow Toyohiro , Masahara Meishoku 
Published: February 2020

It is well known that the high-k interpoly dielectric (IPD) layer is important for further scaling down of floating gate (FG) type flash memory to improve the gate coupling ratio [1, 2]. Therefore, the high-k Al2O3 layer has already been used as a blocking layer in the charge trapping (CT) type planar and bulk FinFET flash memories [3-5]. However, the high-k Al2O3 has not been used as an IPD layer in the FG type SOI-FinFET flash memories, to our knowledge. In this work, we introduce the high-k Al2O3 into the FG type triangular-fin (TF) and rectangular-fin (RF) channel SOI-FinFET flash memories, and investigate the effects of fin shape and IPD layer material on the electrical characteristics of the fabricated FG type SOI-FinFET flash memories. In the device fabrication, we used (100) and (110) oriented SOI wafers to fabricate TF and RF channels by using the orientation dependent wet etching [6]. A 30-nm-thick n+ poly-Si layer was used as the FG material. Figure 1 shows the cross-sectional STEM images of the fabricated FG-type SOI-FinFET flash memories with different channel shapes and different IPD layers. Figure 2 shows the P/E characteristics of the fabricated 3 kinds of SOI-FinFET flash memories at the same P/E condition. It is clear that a higher P/E speed, a larger memory window and a lower-voltage operation are achieved in the TF-ONA device as compared to the TF-ONO and RF-ONA ones. This result indicates that a high-k Al2O3 layer is very useful for enhancing memory window due to the improved gate coupling, and the TF channel is very suitable for the low-voltage operation thanks to the high-k of Al2O3 and the electric field enhancement at the sharp foot edges of a TF.
[1] B. Govoreanu et al., IEDM 2006, p. 479. [2] H.-T. Lue et al., IEDM 2011, p. 203. [3] C. H. Lee et al., IEDM 2003, p. 613. [4] S.-K. Sung et al., VLSI 2006, p.106. [5] B. J. Tang et al., IEDM 2011, p. 219. [6] Y. X. Liu et al., VLSI 2010, p.101.

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Control of the Surface Chemistry of Magnetron-Deposited Silicon Nitride Etched with Various Wet Treatments
Authors: Brunet Marine , Gouget-Laemmel Anne-Chantal , Aureau Damien , Guillemot Francois , Etcheberry Arnaud , Ozanam François 
Published: February 2020

Silicon nitride is a common material in the microelectronic industry, thanks to its dielectric, chemical and mechanical properties. However, when exposed to atmosphere, the silicon nitride layer tends to oxidize. This work presents several efficient ways to remove this native oxide layer while controlling the resulting surface chemistry. Achieving such a control may provide a reliable starting point for further surface functionalization by organic molecules.
The silicon nitride thin films are deposited by magnetron sputtering. The silicon nitride stoichiometry can be tuned by varying the gas fluxes (Ar, N2) during deposition. Three wet treatments are studied and optimized: hydrofluoric acid (HF), ammonium fluoride (NH4F) and potassium hydroxide (KOH). The treatment efficiency is controlled by X-ray Photoelectron Spectroscopy measurements (XPS). The surface chemistry is investigated by combining Attenuated Total Reflection InfraRed (ATR-IR) and XPS measurements.
All of the three chemical treatments yield the removal of the native oxide, albeit at different rates. HF solution is an efficient and fast etching treatment of silicon nitride. On the resulting surface, fluorine is detected by XPS, suggesting the presence of Si-F bonds. No Si-H bonds are detected on the etched surface by ATR-IR, in agreement with the literature results.
NH4F solution is as efficient as HF in etching the silicon nitride surface, although much slower. This also leads to Si-F bonds, but in a lesser amount than after a HF treatment. KOH can also etch the native oxide of the silicon nitride layer. In this case, the resulting surface contains more oxygen than with the two previous solutions, a likely fingerprint of the presence of surface Si-OH species. Interestingly, the etching rate of the bulk silicon nitride appears much reduced upon etching with KOH as compared to HF.
The formation of Si-H bonds can be forced thanks to a H2plasma treatment performed after the wet native oxide stripping. As shown in the figure, a broad SiH stretching vibration builds up in the infrared spectra upon submitting the silicon nitride film to such a plasma treatment at room temperature. The detailed analysis of XPS signals of samples submitted to various treatment durations shows that the initial surface Si-F bonds are not broken by the plasma, but that the silicon nitride film is progressively etched during the treatment. The film roughens during its dry etching, accounting for the large increase of the SiH signal.
An important parameter we also investigated is the silicon-nitrogen ratio. The chemistry of the etched surface is highly dependent on this ratio. As shown in the figure, with a silicon-rich silicon nitride layer, a HF treatment leads to the formation of some Si-H bonds on surface.

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A Ring Type Residue Formation in Post Cu CMP Cleaning
Authors: Kim Hojoong , Liim Dong Hyun , Moon Jinok , Kim Jun-Yong , Hwang Hasub , Kim Taesung 
Published: February 2020

A chemical mechanical planarization (CMP) of copper (Cu) damascene structure is prone to defect formation due to variety of chemical agents in slurry and chemical complex formation. In post CMP cleaning process, which should remove such defects, a mechanical scrubbing of wafer by porous and elastic brushes are eligibly used. Although, chemical effects are the main mechanism of defect detachment and dissolution during cleaning process, mechanical effects also play key role by transportation of chemical agent and discharge of reacted species.
The most relevant defect caused by mechanical effect is ring shaped scratch due to exceeding contact pressure. In this study, however, we focused on ring shaped residue after post Cu CMP cleaning which is not caused by direct solid contact. To investigate root cause, analysis are carried out such as chemical composition of residue, surface charge map on a wafer, kinematic analysis on brush and wafer motion, and fluid dynamic simulation on chemical motion. In conclusion, it is revealed that both chemical and mechanical effects are interacted to form ring shaped residue. Elimination of defects by chemical effect is suppressed by mechanical motion of brush and chemical fluid.

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Advanced Process Control for Variability Control in Chemical Mechanical Polishing Process
Authors: Koli Dinesh R , Wan Hsiang Liang Rachel , Kim Hong Jin 
Published: February 2020

With semiconductor technologies driving towards sub 14nm nodes, FIN based field effect transistors (FINFETs) have been the preferred design to meet device power and performance requirements. At the core of FINFET transistor design is gate last/replacement metal gate (RMG) integration scheme due to the advantages in thermal budgets. Chemical mechanical planarization has evolved from planarization technique to technology enabler for this integration scheme. Replacement metal scheme has its own share of challenges- the integration scheme is quite complex. Chemical mechanical planarization (CMP) plays a key role in enabling this integration with various CMP steps supporting dummy poly gate formation, poly removal and replacement metal gate formation. The final gate height of the replacement metal gate is one of the most important parameters controlling device resistance. Even a change of 1nm gate height can result in overall variation of 5ohms/sq resistance. This requires CMP to control gate height as tightly as possible for every wafer. The two important factors contributing to the overall gate height variation are upstream processes and the metal gate CMP process itself. It is well known that CMP has its own variability in removal rate depending on consumable life resulting in unstable gate height. The gate height variation needs to be controlled within wafer and every wafer. A dedicated metrology tool connected to the polishing tool has been employed for many years to measure wafer thickness parameters. This onboard metrology tool is used to measure every wafer and the data is used to develop automated process control to improve overall within wafer and wafer to wafer variation. A two fold approach is used to achieve this. Integrated automated process control (iAPC) is initially used to control wafer to wafer variation and furthermore, zonal integration automated process control is used to improve within wafer uniformity. The basic concept is to use metrology data collected from each wafer and create a model to adjust polishing time to achieve desired final gate height target. Using these two approaches, gate height control of less than 5nm has been demonstrated consistently. Both these approaches will be discussed in detail.
Immersion Metrology for CMP Pad Monitoring
Authors: Moore Terry , Arasanz Andres 
Published: February 2020

Selectivity between materials being polished over the lifetime of the CMP consumable set will typically change. Changes in selectivity overtime are varied and complex, but one main contributor identified in this study using Sensofar immersion metrology, is the changing state of the polishing pad asperities overtime (aka Glazing).
This study (of a damascene process) demonstrated;
--> Successful monitoring of the same “wet” polishing pad while on the platen.
--> Identification of multiple points in usage when glazing occurred
--> Characterization of successful interventions to reverse the glazing effect
--> Successful return to target selectivity
--> Longer consumable lifetime
--> Reduced manufacturing downtime (MTTR).

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Development of Cobalt Chemical Mechanical Planarization Slurries By Electrochemical/Surface Analytical Screening and Polishing Studies
Authors: Theivanayagam Murali Ganth , Wang Hongyu , Cohen Jamie , VanHanehem Matthew , Sabo Tim , DeNardi Stephan 
Published: February 2020

As the technology nodes in integrated circuit (IC) fabrication continue to approach molecular dimensions, the defectivity and planarization provided by conventional chemical mechanical planarization (CMP) processes are no longer sufficient. Therefore, it is necessary to develop new chemistries and innovative screening techniques to solve difficult CMP challenges, including the use of new materials such as cobalt in advanced IC fabrication. For advanced nodes at 14 nm and below, cobalt is currently being implemented on top of Ta/TaN barrier layers and below the copper seeds for the first few metal lines, due to its better conformational coverage within high aspect ratio features and good adhesion to copper. In addition, replacing copper with cobalt in the trenches of interconnect lines for the first few metal layers in the BEOL has demonstrated lower resistivity at smaller dimensions, therefore cobalt interconnects are being considered for < 10 nm nodes for M1 and M2. All these new integration schemes require CMP to achieve planarity with requirements such as low dishing, defectivity, roughness, and tunable selectivity depending on the stack.
Under CMP conditions, however, cobalt can suffer from corrosion and static-etch issues, especially when in contact with copper (galvanic corrosion), due to the lower standard reduction potential of cobalt in aqueous solutions across a broad pH range. The corrosion issues must be solved in CMP slurries that deal with cobalt processes (both liner and bulk/plug) to successfully commercialize cobalt-based IC design for next generation semiconductor manufacturing. In this poster, we will discuss the results and learnings from corrosion inhibitor screening techniques such as electrochemical, static-etch, and quartz crystal microbalance (QCM) studies and their correlation with polishing results for developing cobalt slurry formulation platforms. Furthermore, fundamental understanding on the effects of pH and slurry components such as complexors/oxidizers/corrosion inhibitors on the corrosion and removal rate behavior of cobalt films will be discussed.
Role of Cerium Oxide Surface Chemistry in Adsorption of Polyacrylic Acid in CMP Slurries
Authors: Saraf Shashank , Mesbahi Ali , Harper James , Seal Sudipta 
Published: February 2020

Chemical mechanical polishing (CMP) slurries formulated of cerium oxide nanoparticles (CNPs) and polyacrylic acid (PAA) are widely used in shallow trench isolation (STI) application. The critical parameter in slurry formulation is the amount of PAA which determines the extent of its adsorption on CNPs and the excess amount. The adsorption of PAA on CNPs results in a softer surface and prevents defects such as scratches on the wafer surface. The excess PAA selectively adsorbs on silicon nitride, slowing down its etching as compared to silicon dioxide.1 Therefore, the understanding of PAA adsorption on CNPs in a slurry formulation is critical to predict the CMP slurry characteristics.
In previous studies the adsorption of PAA on CNPs has been widely studied;2 however there is still a lack of understanding between adsorption behavior of PAA and the interfacial properties of CNPs. Here, we have systematically investigated the PAA adsorption on ceria slurries and correlating it to the CNPs interfacial properties. Three different commercial ceria slurries were obtained having similar hydrodynamic size, but different surface area as determined using BET. The catalytic properties of CNPs is assessed from the ratio of Ce3+/Ce4+ on its surface, determined using XPS.3 The surface functionalization of CNPs is evaluated from FTIR and NMR depicting three different types of organic moieties resulting in different zeta potentials. Lattice strain and grain size are another important parameter which signifies the internal energy of CNPs. These parameters were calculated using Williamson-Hall plots obtained from the XRD curve. The adsorption isotherm of PAA on CNPs is determined by measuring the carbon content in the supernatant separated from the CNPs using centrifugation. The carbon content is measured using TOC analyzer and the amount of PAA adsorbed on CNPs is calculated by mass balance equation.
1. Ronay, M., Selective polishing with slurries containing polyelectrolytes. Google Patents: 2005.
2. (a) Saraf, S.; Neal, C. J.; Das, S.; Barkam, S.; McCormack, R.; Seal, S., Understanding the Adsorption Interface of Polyelectrolyte Coating on Redox Active Nanoparticles Using Soft Particle Electrokinetics and Its Biological Activity. ACS applied materials & interfaces
2014,
6 (8), 5472-5482; (b) Kim, S.; So, J.-H.; Lee, D.-J.; Yang, S.-M., Adsorption behavior of anionic polyelectrolyte for chemical mechanical polishing (CMP). Journal of colloid and interface science
2008,
319 (1), 48-52.
3. Pirmohamed, T.; Dowding, J. M.; Singh, S.; Wasserman, B.; Heckert, E.; Karakoti, A. S.; King, J. E.; Seal, S.; Self, W. T., Nanoceria exhibit redox state-dependent catalase mimetic activity. Chemical communications
2010,
46 (16), 2736-2738.
(Invited) Magnetron Sputtering for Deposition of Photocatalyst Nanostructures on Transparent Conductive Oxides for Solar Applications
Authors: Kruth Angela 
Published: February 2020

Photocatalysis has attracted an enormous amount of research interest, in especially with regard to applications such as solar hydrogen generation as well as pollutant degradation. Main research target is the development of corrosion-stable core candidate materials that are able to perform under the abundant visible light in the solar spectrum. Two main approaches are being employed, the development of visible light-sensitive semiconductors and sensitisation of wide band-gap semiconductors. In materials synthesis, plasma-enhanced surface modification and layer deposition methods are based on the presence of non-equilibrium states of reactive species in a plasma environment. They are therefore able to overcome limitations of traditional catalyst synthesis methods, giving rise to new reaction pathways and resulting in unique properties of nanomaterials.
This presentation reports on recent work on development of DC magnetron sputtering processes for deposition of TiO2 and WO3 semiconductor layers as well as RF magnetron deposition for synthesis of N-doped graphite electrodes on TCO. Electrode properties are characterised by means of XRD, TEM, UV/Vis, XPS, Raman spectroscopy and photoelectrochemical characterisation including IMVS/IMPS and IPCE measurements. Furthermore, plasma-enhanced deposition methods for surface enhancement of photocatalysts layers by nanoparticles and polymer-encapsulation are also discussed.
(Invited) Plasma-Liquid Interactions for Nanoparticle Synthesis, Functionalization and Biomedical Interactions
Authors: Bruggeman Peter J 
Published: February 2020

Non-equilibrium atmospheric pressure plasmas interacting with liquids offer a unique source of highly reactive chemistry beneficial for many applications in biology, medicine and advanced materials manufacturing. Plasma-liquid interactions can involve synthesis of nanoparticles (NPs) and inactivation of pathogens. While the underlying mechanisms of these processes are poorly understood, the application potential is enormous.
The presentation will highlight some examples of reaction pathways responsible for the synthesis of AgNPs at the plasma-liquid interface. This will include a detailed analysis of the reduction mechanism of Ag+, the initial step for the formation of NPs in solution, through various mechanisms proposed in literature including solvated electrons, UV photons and hydrogen atoms.
Plasmas are typically oxidizing and not reducing environments as they produce an abundant source of reactive oxygen species (ROS). We will present the possibility of using these ROS for the functionalization of NPs and in particular the generation of luminescent and hydrophobic water-soluble silicon quantum dots. In addition, we will discuss the importance of these ROS in the inactivation of pathogens in solutions. We will conclude with an overview of the challenges and opportunities ahead.