bluuebunny/crossref_metadata_2025 huggingface dataset:
Integration Challenges and Opportunities for Nanometer Scale CMOSFET with Metal/High-k Gate Stack
Authors: Song S. , Hussain M. , Barnett J. , Park C. S. , Park C. , Kirsch P. , Lee B.H. , Jammy Raj
Published: September 2007

As MOSFET scales below 45nm, conventional SiO2 cannot sustain equivalent oxide thickness (EOT) and leakage current requirements set in the International Technology Roadmap for Semiconductors (ITRS), due to the limitation of physical-thickness scaling, and high tunneling current [1]. Metal gate and high-k dielectric have been extensively studied to overcome the limitation of conventional poly gate and SiO2 technology. Although recent advancements of the technology enable the metal gate and high-k dielectric to be implemented in actual manufacturing, several issues remain associated with integration the new materials in CMOS field-effect transistors (FETs). This paper will introduce various integration schemes for fabricating dual metal gate CMOSFET, and review pros and cons of each approach to propose general integration guide for the desired application.
Formation of Silicided Hyper-Shallow p+/n- Junctions by Pulsed Laser Annealing
Authors: Pey Kin L. , Ong K. K. , Lee P. S. , Setiawan Y. , Wang X.C. , Wee A.T.S. , Lim G.C.
Published: September 2007

In this invited talk, we first review various methods for the formation of p+/n junctions of depth of less than 40nm using excimer pulsed laser annealing technique of 248nm wavelength. The characteristics of junctions formed using single and multiple-pulsed shallow melt and non-melt laser annealing on amorphous and single crystalline Si substrate would be compared. To overcome the defect-related enhanced diffusion during pulsed laser annealing, novel junction engineering methodology using implantation generated defects such vacancies is illustrated. Methods employing ultra-low energy implants with laser annealing for junctions less than 25 nm are proposed. In addition, we will also talk briefly about the potential application of the laser annealing to be used for an ultra-low thermal budget silicide formation.
High Volt Mixed Signal Integration Challenges
Authors: Tyler Matthew , Naughton John J.
Published: September 2007

A high voltage, fault tolerant PMOS transistor and matched BiModal SCR have solved the unique integration challenges presented by applications in automotive electronic. These include; load dump, reverse battery, and short to battery protection. Often, these demands require multi-well isolation precluding the use of a standard CMOS process technology. This work presents a novel SoC type of solution that has been implemented in a mature single well technology. This further provides a reliability and cost structure more desirable to the end customer.
Formation of Fe3Si/Ge/Fe3Si Multi-layer by Double Heteroepitaxy on High Quality Fe3Si/Ge Substrate for Spintronic Application
Authors: Ueda Koji , Ando Yuichiro , Kumano Mamoru , Sadoh Taizoh , Maeda Yoshihito , Miyao Masanobu
Published: September 2007

Double heteroepitaxial growth of Fe3Si/Ge on high quality Fe3Si/Ge substrates has been investigated by low-temperature (<300oC) molecular beam epitaxy. Reflective high-energy electron diffraction measurements suggested that Fe3Si and Ge layers were epitaxially grown on Fe3Si/Ge substrates, though the surface morphology became rough. X-ray diffraction measurements revealed that a small amount of Fe3Si(110) was included in the top Fe3Si layers. Transmission electron microscopy measurements indicated that stacking faults were formed in the intermediate Ge and the top Fe3Si layers. Improvement of crystal quality of the intermediate Ge layer is essential to realize high quality Fe3Si/Ge/Fe3Si multi-layers.
EOT Measurement of Ultra-Thin Gate Dielectrics using the Tunneling Current Regime
Authors: Dos Santos Sebastião G. , Nogueira Willian , Toquetti Leandro Z.
Published: September 2007

Presented in this work is a measurement method to obtain the Equivalent Oxide Thickness (EOT) using the tunneling current regime for ultra-thin gate dielectrics ranging from 1.5 to 16 nm. With the aid of the I-V characteristic of MOS capacitors in a low electric-field range (5-7 MV/cm), EOT was obtained from the slope of the ln(I/Vox2) versus 1/Vox graph for direct or Fowler-Nordheim tunneling current regimes. The average EOT uniformity was obtained for representative populations of tested MOS capacitors (at least a hundred per wafer) and, comparing with the results obtained from C-V measurements, the method was validated.
Junction Photovoltage (JPV) Techniques for Ultra-Shallow Junction Characterization
Authors: Faifer Vladimir N. , Current Michael I. , Schroder D. , Clarysse Trudo , Vandervorst Wilfried
Published: September 2007

A non-contact method for measurement of sheet resistance and leakage current (RsL) for ultra-shallow junction (USJ) characterization is described based on analysis of frequency-dependent junction photovoltages from p-n junctions . Theoretical, device-simulated and measured photovoltages, sheet resistance as well as RsL and reverse-biased diode currents are compared. The linkage between RsL recombination currents and end-of-range implant damage in USJ/halo profiles and deletion layers is described. The addition of a Halo profile to a USJ results in increased in sheet resistance and leakage current due to changes in the junction depth and depletion layer conditions. Measured recombination leakage currents for implanted and CVD-grown USJs are compared with calculation and show good agreement.
Electron Holography as Characterization Tool for 2-D Analysis of p-n Junctions
Authors: Gribelyuk Michael A. , Domenicucci Anthony , Ronsheim Paul , McMurray Jeffrey , Gluschenkov Oleg
Published: September 2007

We review formation of an electron hologram in TEM for analysis of p-n junctions in semiconductor devices. It is shown on the basis of comparison of results of electron holography and SIMS that the method can provide quantitative information directly, i.e. without consideration of "dead layers" in both bulk Si and SOI structures. Unique information provided by electron holography addresses a wide range of problems concerned with understanding dopant diffusion, process integration and physical failure analysis. In particular, it is proved that laser anneal does not cause lateral dopant diffusion of As to resolution of the method and demonstrated that junction overlap can be achieved with "laser-only" integration scheme We show how position of p-n junctions prior to annealing can be deduced from holography analysis to help tune process integration. Examples concerning physical failure analysis cover blocked implants, effect of STI proximity on dopant depletion.
Carrier Lifetime Measurements in Silicon for Photovoltaic Applications
Authors: Pavelka Tibor , Pap Aron , Szilagyi Gyorgy
Published: September 2007

The present paper gives an overview of the possibilities of microwave detected photoconductivity decay technique (µ-PCD) in the field of photovoltaics with special emphasis on the practical aspects. Applications are followed all through the manufacturing process from feedstock throughout the form of ingot, block, as-cut wafer, processed wafer up to finished cell. Future chances of the technique for thin film solar cell investigations are also covered. Key problems for carrier lifetime measurements, i.e. the role of surface recombination and separate detection of iron contamination are discussed in details. Whenever relevant a comparison with standard microelectronic semiconductor applications is given. In addition to laboratory use implementations in a manufacturing environment as inline tools are also described.
In-Situ Measurement Method and Rate Theory for Clarifying Multi-Component Organic Compounds Adsorption and Desorption on Silicon Surface
Authors: Habuka Hitoshi , Yamaya Daisuke
Published: September 2007

Surface concentration of organic compounds, isopropanol and diethyl phthalate, on a silicon surface in a single-component system and in a two-component system was measured in-situ using a quartz crystal microbalance in ambient nitrogen with controlled humidity. The measured behavior was analyzed based on the rate theory. The surface concentration in a steady state changes corresponding to the gas phase concentrations of isopropanol and diethyl phthalate. The measurement results are interpreted under the assumption that the larger limit of surface concentration in a multi-component system depends on the rate parameters and the gas phase concentration of the organic compounds.
Integration of Electrochemically Deposited Cu with Plasma Enhanced Atomic Layer Deposition-Grown Cu Seed Layers
Authors: Wu Liqi , Zeng Wanxue , Eisenbraun Eric
Published: September 2007

A promising plasma enhanced atomic layer deposition (PEALD) Cu process has been developed, and PEALD Cu layers have been investigated for use in multilevel damascene metallization. Continuous and conformal PEALD Cu layers as thin as 12 nm were deposited on blanket and high aspect ratio patterned substrates. The effects of hydrogen plasma pretreatments on the material and integration properties of the PEALD Cu process have been studied. Plasma pretreatments were observed to improve Cu nucleation and enable lower Cu resistivity and surface roughness. Void-free electrochemically deposited Cu fill was achieved on PEALD Cu-seeded high aspect ratio via structures. The plated Cu films possess a strong (111) texture inherited from the PEALD Cu seed layer.
Molecular Layer Deposition of Organic and Hybrid Organic-Inorganic Films
Authors: George Steven , Dameron Arrelaine , Du Yijun , Adamczyk Nicole M. , Davidson Stephen
Published: September 2007

Polymeric films can be grown by a sequential, self-limiting surface chemistry process known as molecular layer deposition (MLD) that is very similar to atomic layer deposition (ALD). The MLD reactants are typically monomers for step-wise condensation polymerization and can yield completely organic or hybrid organic-inorganic alloys. This study will illustrate the MLD of organic films with the growth of nylon 66 and poly(p-phenylene terephthalamide) [PPTA]. Hybrid organic-inorganic MLD will also be demonstrated using the growth of poly(aluminum ethylene glycol) [PAEG]. The nylon 66 and PPTA MLD and the PAEG MLD will be examined with in situ transmission Fourier transform infrared (FTIR) spectroscopy, in situ quartz crystal microbalance (QCM) and ex situ x-ray reflectivity (XRR) measurements. These investigations will reveal the self-limiting chemistry and linear growth expected for MLD processing.
Copper Nano Film Formation Using Electrochemical ALD
Authors: Thambidurai Chandru , Jayaraju Nagarajan , Kim Youn-Geun , Stickney John L.
Published: September 2007

This paper concerns the formation of Cu nano films using atomic layer deposition (ALD) via surface limited redox replacement (SLRR). The automated flow cell deposition system was employed to make Cu nano films using100, 200 and 500 deposition cycles. The open circuit potential (OCP) was used during replacements to monitor progress in the replacement, and was found to approach 0 mV upon removal of the Pb atomic layer. This ensured complete replacement and that the surface was covered with Cu. The replacement efficiency was calculated to be 93 % from the anodic stripping of Cu films in blank solution. The Cu film deposited appeared homogeneous using SEM and optical microscope. No Pb was present in the Cu nano film, determined using EPMA. However, the more negative the potentials used to deposit the sacrificial Pb layers, below the -0.44 V used, the more Pb found in the resulting deposit. A prominent Cu(111) peak was evident using XRD.
Evaluation of Novel Sr Precursors for Atomic Layer Deposition of SrO Thin Film
Authors: Kim Ki-Chul , Cho Kyuho , Lee Kwanghee , Kim Younsoo , Choi Jae H. , Lim Jae-Soon , Kim Jin Y. , Kim Wan-Don , Kwon Oh S. , Tak Yong S. , Chung Jeong-Hee , Kim Young-Sun , Kim Sung-Tae , Han Woosung
Published: September 2007

Novel strontium precursor - bis(1-methoxy-2,2,6,6-tetramethyl-3,5-heptanedionato)strontium (Sr(MTHD)2) - was prepared and its deposition properties were evaluated.High vapor pressure and excellent conformality of Sr(MTHD)2 make it promising candidate for ALD precursor to deposit high-k dielectric materials such as SrTiO3.
Ferromagnetic Nanostructures by Atomic Layer Deposition: From Thin Films Towards Core-Shell Nanotubes
Authors: Nielsch Kornelius , Bachmann Julien , Daub Mihaela , Jing Jing , Knez Mato , Gösele Ulrich , Barth Sven , Mathur Sanjay , Escrig Juan , Altbir Dora
Published: September 2007

Nickel, cobalt and iron oxide nanotubes were obtained by atomic layer deposition (ALD) into the pores of alumina membranes. Initially, a metal oxide film was grown by the reaction of a precursor vapor of NiCp2 (nickelocene), CoCp2 (cobaltocene) or FeCp2 (ferrocene) with ozone, respectively. Subsequently, the metal oxide film was reduced in hydrogen atmosphere and converted to a metallic ferromagnetic phase with low-degree of surface roughness. In a similar manner, Fe3O4 films have also been obtained by the atomic layer deposition of Fe2O3 films based on the reaction of water and iron(III) tert-butoxide (Fe2(OtBu)6), followed by a hydrogen reduction to Fe3O4 after the ALD process. By conformal coating of self-ordered Al2O3 membranes, arrays of magnetic nanotubes with diameters down to 30 nm and wall thicknesses of less than 3 nm have been achieved. The magnetic properties of the nanotube arrays as a function of wall thickness and tube diameter have been studied by SQUID magnetometry. Atomic layer deposition (ALD) was proven to be a very suitable method for the conformal deposition of magnetic thin films in pore structures of high aspect ratio, while offering high uniformity and precise tuning of the layer thickness and the magnetic properties.
Fabrication of Nanoscale Tubular Structures and Capsules of Oxides by ALD
Authors: Bae Changdeuck , Kim Shihyeong , Shin Hyunjung , Kim Jiyoung
Published: September 2007

Uniform-sized metal oxide nanocapsules, termed nanoampoules, have been fabricated. Hollow nanopipes of titania (TiO2) were first fabricated onto either a polymeric template or porous anodized aluminum oxides with monodisperse cylindrical holes by using atomic layer deposition (ALD) techniques. The inner volume of individual nanopipes can be tailored precisely by controlling the thickness of layers deposited with ALD. This encapsulation strategy should have potential for application in ideal drug delivery systems, gene therapy, cosmetics, inks, chemical sensors or pigments.
Spatially Controlled Atomic Layer Deposition in Porous Membranes
Authors: Elam J. , Libera Joseph A. , Stair Peter C. , Pellin Michael J.
Published: September 2007

This manuscript introduces a new technique for depositing materials at controlled depths within porous substrates. This technique uses the passivating effect produced by one ALD precursor to prevent the adsorption of a second ALD precursor. For example, a surface exposed to trimethyl aluminum is not reactive towards diethyl zinc. This effect, combined with Knudsen diffusion through the nanopores in which the reactant exposure times dictate the depth of penetration of the ALD layer, enables spatially controlled "stripe coating" within porous supports such as anodic aluminum oxide (AAO) membranes. We have used this method to deposit stripes of ZnO, TiO2, V2O5, and Nb2O5 at specified depths in AAO membranes. The stripes were visualized by cross-sectional elemental mapping of the coated AAO membranes. The factors controlling the stripe locations and widths were identified by comparing the experimental results with the results of Monte Carlo simulations. This new technique opens up potential applications in sensors, separation devices, and multi-step catalysts.
Atomic Layer Deposition for CMOS Scaling: High-k Gate Dielectrics on Si, Ge, and III-V Semiconductors
Authors: Frank Martin
Published: September 2007

We review the impact of oxide-semiconductor interface chemistry and precursor choice on the quality of novel field-effect transistor gate dielectrics grown by atomic layer deposition (ALD). Focus is on hafnium- and aluminum-based high-permittivity ('high-k') gate dielectrics on silicon and on high carrier mobility (germanium, gallium arsenide) channels. We shed light on the ways processing parameters (choice of materials; surface preparation; high-k dielectric deposition process) determine stack structure (continuity of the high-k layer; interfacial oxide thickness; detrimental channel-dielectric interactions) and hence electrical quality. Trends are rationalized based on thermodynamic properties of the semiconductors, dielectrics, and metal-organic precursors involved. This may serve as a basic guideline for ALD precursor selection.
Corrosion Suppression During Wet Processes in FEOL and BEOL for 45nm Node and Beyond
Authors: Aoki Hidemitsu , Watanabe Daisuke , Hotta Saori , Kimura Chiharu , Sugino Takashi
Published: September 2007

Galvanic corrosion of metal gates in front end of line (FEOL) is a serious problem during wet processes for technology devices of 45 nm node and below. We attempt galvanic corrosion to suppress with high selectivity for High-k/SiO2 using a water-less solution of organic solvent and HF. We succeeded in suppressing corrosion of metal gates using IPA + HF solvent for FEOL processes. In the back end of line (BEOL), corrosion suppression for Cu wiring with porous low-k is an important issue. In particular, an environmentally safe inhibitor instead of BTA is important. This paper reports the technology for the suppression of corrosion of metal gates and an environmentally safe inhibitor (Adenine) for Cu/low-k.
Using Megasonics to Extend Chemical Cleans for 45nm Technology
Authors: Franklin Cole , Fan Yan , Brause Eric , Nguyen Vu
Published: September 2007

Aqueous and solvent chemicals are widely used in the semiconductor industry and as the technology nodes shrink device makers are working to extend these cleaning fluids to the next technology node. Internal data shows megasonic agitation can enhance polymer removal without complete dissolution for both aqueous and solvent chemicals. However, today, front end of line post reactive ion etch polymer removal clean steps are preformed with cheap aqueous commodity chemicals. So, this paper will look into the possibility of extending aqueous cleans to the next technology node using megasonic agitation.
Dissemination of Metallic Contamination During IC Manufacturing
Authors: Danel Adrien , Borde Yannick , Maurel Adrien , Laetitia Brunon , Royer Agnes
Published: September 2007

The dissemination of metallic contamination occurring during wafer handling is of primary importance for the management of cross contamination issues. This work describes a protocol used to estimate the percentage of contamination transferred from a contaminated wafer to another one via contact on solid surfaces involved during handling. Results suggest that particles size is the most important parameter on the global cross contamination coefficient named K. For sub µm particles, the transfer is low, K ranging from 0 to 10%. Above a few µm, particles are very easily transferred from contaminated wafers to handling surfaces, with a coefficient K1 which can reach 100%. The decontamination of handling surfaces cycling clean wafers or using wet wipes has also been investigated. For situations leading to high K percentages, efficient and fast cleaning protocols can be applied. This work also discusses the interaction forces between particles and substrates to explain the observed tendencies.
A New Approach for FEOL Critical Wafer Surface Cleaning
Authors: Fischer Thomas , Puri Suraj , Hoyer Ronald , Wostyn Kurt L. , Janssens Tom
Published: September 2007

As the semiconductor industry moves to processes for line widths of 65nm and beyond, there is a need for a new cleaning technology which addresses issues of the nano world, especially the concern of silicon / silicon oxide loss on the devices during each of the cleaning step. Particle removal efficiencies were obtained at extremely low ammonia concentrations reaching down to parts per billion. Reducing concentrations of ammonia down to a single digit ppm and then to a much lower concentration, makes use of a new dimension of physics: Quantum Electro Dynamics and the formation of "clusters". It is observed for the first time in a semiconductor manufacturing environment that the particles detached from wafer surfaces by megasonic energy, are removed effectively by the zeta potential produced by the "water clusters" enabling us to compare the performance of the clustered clean to the standard RCA clean of the fab.
Via Failures in a Plug Process Due to Incomplete Via Clean Chemistry Removal
Authors: Florence Deborah M. , Burtosky Sheila , Cioffi Chris , Doub Jason , Mortensen Keith , Russell Chuck
Published: September 2007

Reliable via formation requires complete polymer removal in vias prior to barrier deposition to obtain low electrical resistance contacts between metal conductor layers. A failure mechanism of high resistance and open vias was observed due to aluminum polymer in the via either partially or fully blocking barrier deposition onto the metal layer at the via bottom. This failure mechanism involved a breach of the titanium-nitride (TiN) anti-reflective coating (ARC) layer over the aluminum in the underlying conductor metal layer, allowing via clean chemistry to react with the aluminum. An aluminum polymer is formed, partially or fully blocking barrier deposition. Experimental data show that open via occurrences worsened with increased sit-time between via clean and the via barrier deposition step. In this paper we will discuss the mechanism causing high resistance or open via failures due to incomplete hydroxylamine (HDA) chemistry removal.
Liquid Infiltration Mechanism for Cleaning in Deep Microholes
Authors: Ota Katsuhiro , Tsutsumi Atsushi
Published: September 2007

Liquid infiltration mechanism for cleaning high aspect ratio trenches and microholes of highly integrated semiconductor devices was considered by theoretical and experimental methods. It is theoretically predicted that liquid does not infiltrate into microhole with non-wettable liquid-solid contact surface. Increasing liquid pressure and/or decreasing inside gas pressure overcome the surface tension to infiltrate liquid into non-wettable microholes. On the other hand liquid can infiltrate into wettable microholes independent of microhole size. These theoretical predictions were confirmed by using non-destructive observation of high aspect ratio model structures.
A Novel Concept for Contact Etch Residue Removal
Authors: Vos Ingrid J. , Hellin David , Demuynck Steven , Richard Olivier , Conard Thierry , Vertommen Johan , Boullart Werner
Published: September 2007

A novel cleaning concept, Confined Chemical Cleaning, and its applications in post contact etch residue removal is presented. The technique combines short and controlled exposure times with integrated dry etch/wet clean processing for residue removal.
Surface Preparation in CMP Process; Post CMP Cleaning and Defects
Authors: Park Jin-Goo , Kim Tae-Gon
Published: September 2007

Defects due to CMP processes should be removed for next processing step. The zeta potential of slurry particle and substrate has been considered to be a critical factor in terms of particle adhesion and removal. The fundamental research such as the calculation interaction force based on DLVO theory and the measurement of adhesion forces by AFM between slurry particle and wafer surfaces can enhance the understanding of cleaning mechanism and development of cleaning process. This paper gives an overview of post CMP cleaning process from fundamentals to the current and future.
Tight Distribution of Dielectric Characteristics of HfSiON in Metal Gate Devices
Authors: Hasunuma Ryu , Naito Tatsuya , Tamura Chihiro , Uedono Akira , Shiraishi Kenji , Umezawa Naoto , Chikyow Toyohiro , Inumiya Seiji , Sato Motoyuki , Tamura Yasuyuki , Watanabe Heiji , Nara Yasuo , Ohji Yuxuru , Miyazaki Seiichi , Yamada Keisaku , Yamabe Kikuo
Published: September 2007

Leakage current characteristics with significantly reduced dispersion were achieved for HfSiON gate dielectric film by selecting TiN gate electrode with low reactivity, compared to the conventional poly-Si gate. The breakdown lifetime and its characteristic homogeneity were also enormously improved. With intensive study on these electrical characteristics, it was concluded that the concentration of oxygen vacancy was significantly reduced, giving rise to the homogeneity improvement. Moreover, we have shown an explanation for the dielectric breakdown in terms of oxygen transport in the Hf-based dielectric film.
Scaling Down of MOCVD HfSiON to 1nm EOT
Authors: Shi Xiaoping , Rothschild Aude , Everaert Jean L. , Van Elshocht Sven , Date Lucien , Schreutelkamp Robert , Schaekers Marc
Published: September 2007

In this paper we report the down scaling of MOCVD HfSiON gate dielectric towards sub-1nm EOT in Ni-FUSI/HfSiON CMOS devices. HfSiOx process optimization shows that the best device performance is reached for HfSiON gate dielectrics with 60% Hf. N dose engineering in the HfSiON with Decoupled plasma nitridation (DPN) shows that increasing the N dose results in a higher normalized drive current (NIdsat) and a reduced Tinv. However a higher N dose also causes a higher gate leakage (Jg) and more mobility degradation for electrons and holes. The optimum N dose is around 6%. Finally we demonstrate that a dielectric stack of 0.5nm ISSG oxide/2.3nm MOCVD HfSiOx followed by a DPN nitridation achieves 1nm EOT with an excellent controlled gate leakage < 1A/cm2 in Ni-FUSI/HfSiON CMOS devices.
Atomic Layer Deposition of HfO2 on (100) and (110) Oriented Silicon Surfaces
Authors: Nyns Laura , Ragnarsson Lars-Aåke , Hall Lindsey , Delabie Annelies , Heyns Marc , Van Elshocht Sven , Vinckier Chris , Zimmerman Paul , De Gendt Stefan
Published: September 2007

FinFET devices require excellent coverage of the high-k dielectric as is provided by Atomic Layer Deposition (ALD). Because the HfO2 deposition using HfCl4/H2O is controlled by the OH surface density, we studied the impact of crystallographic orientation of the silicon substrate on both its oxidation and HfO2 nucleation. Whereas the (110) orientated substrate oxidizes faster than the (100) silicon, both substrate orientations display the same correlation between the initial HfO2 growth and the thickness of the SiO2 layer. This correlation is characterized by a linear increase, followed by saturation of the HfO2 deposition once the SiO2 thickness reaches approximately 0.4 nm.
Vacancy-Type Defects in MOSFETs with High-k Gate Dielectrics Probed by Monoenergetic Positron Beams
Authors: Uedono Akira , Hasunuma Ryu , Shiraishi Kenji , Yamabe Kikuo , Inumiya Seiji , Akasaka Yasushi , Kamiyama Satoshi , Matsuki Takeo , Aoyama Takayuki , Nara Yasuo , Miyazaki Seiichi , Watanabe Heiji , Umezawa Naoto , Chikyow Toyohiro , Ishibashi S. , Ohdaira T. , Suzuki R. , Yamada Keisaku
Published: September 2007

Vacancy-type defects in MOSFET structures fabricated with high-k (HfSiON) gate dielectrics were studied by monogenetic positron beams. An expansion of open volumes in HfSiON fabricated on Si substrates using atomic layer deposition technique was observed with increasing nitrogen concentration. This fact was discussed in terms of a role of nitrogen in Hf-related oxide using results obtained by first-principles calculation and XPS. MOSFETs fabricated by F-channel implantation technique were also characterized. The major defect species which causes the Vth shift of MOSFETs was identified as vacancy-fluorine complexes (such as V3F2) locate in channel regions of Si substrates. The preset work suggests that positron annihilation can be used to detect microscopic defects in MOSFETs, and it is a useful tool for determining process parameters for MOSFET fabrications with high-k gate dielectrics.
Theoretical Studies on Fermi Level Pining of Hf-Based High-k Gate Stacks Based on Thermodynamics
Authors: Shiraishi Kenji , Akasaka Yasushi , Nakamura Genji , Kadoshima Masaru , Ohta Akio , Miyazaki Seiichi , Watanabe Heiji , Ohmori Kenji , Chikyow Toyohiro , Yamabe Kikuo , Nara Yasuo , Ohji Yuxuru , Yamada Keisaku
Published: September 2007

We have studied Fermi level pinning of Hf-based high-k gate stacks based on thermodynamics by our O vacancy model. Our study shows that FLP cannot be avoided when the system is under thermal equilibrium. O injection to aim O vacancy elimination is hopeless, since O vacancy elimination condition is equivalent to the Si substrate oxidation which leads to the increase in EOT. We also studied the mechanism of FLP induced by H2 anneal. FLP by H2 anneal is governed by the O vacancy annihilation reaction by reducing SiO2 interface layer. Moreover, we briefly discuss the recipe for obtaining band-edge-work-function metals.
The Formation and Characterisation of Lanthanum Oxide Based Si/High-k/NiSi Gate Stacks by Electron-Beam Evaporation: An Examination of In-Situ Amorphous Silicon Capping and NiSi formation
Authors: Hurley Paul , Pijolat Mathieu , Cherkaoui Karim , O'Connor Eamon , O'Connell Dan , Negara Muhammad Adi , Lemme Max C. , Gottlobb Heiner D. , Schmidt Mathias , Stegmaier Katja , Schwalke Udo , Hall Stephen , O.Buiu Octavian , Engstrom Olof , Newcomb Simon
Published: September 2007

The electrical and physical properties of La2O3 based NiSi/High-k/Si structures formed by electron beam evaporation, in-situ amorphous silicon capping and ex-situ NiSi formation are presented for the (100) and (110)Si substrate orientations. The silicon substrate orientation, (100) or (110), does not affect leakage current density or the maximum accumulation capacitance, but does have an impact on interface state densities. The interface states exhibit the electrical signature of Pbo centres for the (100)Si orientation and can be annealed in a H2/N2 ambient. The samples exhibit negligible hysteresis (<2mV). No interfacial silicon layer is observed between the La based high-k film and the silicon substrate. The extracted k value for the La2O3 based thin films is in the range 11-12 suggesting silicate formation. The work indicates an alternative approach for the examination of NiSi/high-k/Si MOS structures without ambient exposure of the high-k layer.
Bulk and Interfacial Oxygen Defects in HfO2 Gate Dielectric Stacks: A Critical Assessment
Authors: McIntyre Paul
Published: September 2007

Oxygen-related point defects can provide fixed charge or act as charge trapping centers in high-k gate stacks and, therefore, their origins and properties are of great interest. In this paper, reported experimental and theoretical results related to oxygen defects in HfO2 gate dielectrics are reviewed critically to assess the relative importance of different defect species in terms of their electrical activity and their contributions to important kinetic processes. In addition to point defects in the "bulk" of HfO2 thin films, defects resulting from differences in oxygen coordination across the internal hafnium oxide/silicon oxide interface are considered.
Challenges with Respect to High-k/Metal Gate Stack Etching and Cleaning
Authors: Vos Rita , Arnauts Sophia , Bovie Inge , Onsia Bart , Garaud Sylvain , Xu Kaidong , Hongyu Yu , Kubicek Stefan , Rohr Erika , Schram Tom , Veloso Anabela , Conard Thierry , Leunissen Leonardus H.A. , Mertens P.
Published: September 2007

The successful implementation of the new high-k dielectrics and metal gate materials for future technology nodes requires a fundamental understanding of their wet etch and cleaning properties. In this paper, wet processing key challenges for introduction of these materials in different integration schemes will be presented.
Crystalline Rare-Earth Oxides as High-k Materials for Future CMOS Technologies
Authors: Osten H. Joerg , Laha Arpuba , Czernohorsky Malte , Dargis Rytis , Bugiel Eberhard , Fissel Andreas
Published: September 2007

We present results for crystalline gadolinium oxides on silicon in the cubic bixbyite structure grown by solid source molecular beam epitaxy. Additional oxygen supply during growth improves the dielectric properties significantly. Experimental results for Gd2O3-based MOS capacitors grown under optimized conditions show that these layers are excellent candidates for application as very thin high-k materials replacing SiO2 in future MOS devices. Epitaxial growth of lanthanide oxides on silicon without any interfacial layer has the advantage of enabling defined interfaces engineering. We will show that the electrical properties of epitaxial Gd2O3 thin films on Si substrates can further be improved significantly by an atomic control of interfacial structures due to a proper treatment of silicon surface prior to the oxide growth.
Characterization of Electrically Active Interfacial Defects in High-k Gate Dielectrics
Authors: Vogel Eric , Sonnet Arif M. , Hinkle Chris L.
Published: September 2007

Issues related to the electrical characterization of interfacial defects in high-κ gate dielectrics using capacitance-voltage, conductance, and charge-pumping are reviewed. Typical data obtained from applying these techniques to MOS devices with high-κ gate dielectrics is presented.
Experimental Study of ALD HfO2 Deposited on Strained Silicon-on-Insulator (sSOI & xsSOI) and SOI
Authors: Gu Diefeng , Tapily Kanda , Shrestha Pragya , Celler George , Baumgart Helmut
Published: September 2007

4 nm HfO2 films are deposited on silicon-on-insulator (SOI) with various amounts of lattice strain and thickness by atomic layer deposition (ALD). After post deposition annealing (PDA), the samples are studied by Rutherford backscattering spectroscopy (RBS), high-resolution transmission electron microscopy (HRTEM), electron energy-loss spectroscopy (EELS), and x-ray photoelectron spectroscopy (XPS). The as-deposited HfO2 film shows good stoichiometry and thickness uniformity. HRTEM images show that while HfO2 films on non-strained SOI becomes poly-crystalline after PDA at 600 oC, HfO2 films on strained SOI still keep amorphous. The strain SOI also suppresses the IL growth during PDA. The EELS and XPS results confirm the interdiffusion across the HfO2/Si interface. The XPS data also show that formation of Hf-O-Si bonds depend on the SOI lattice strain and thickness. The SOI thickness is critical to reduce the formation of silicate in the IL.
A Morphological, Chemical and Electrical Study of HfSiON Films for Inter Poly Dielectric Applications in Flash Memories
Authors: Del Vitto Annalisa , Piagge Rossella , Caniatti Massimo , Wiemer Claudia , Pavia Giuseppe , Sammiceli Francesca , Ravizza Enrica , Grasso Salvatore , Spadoni Simona , Sebastiani Alessandro , Scozzari Claudia , Ghidini Gabriella , Pomarede Christophe , Maes Jan Willem , Alessandri Mauro
Published: September 2007

Due to the continuous scaling down of equivalent oxide thickness requested for inter-poly dielectric material in the next technology nodes, the Oxide-Nitride-Oxide structure is not able anymore to guarantee charge retention because of high leakage current. An alternative stack with higher dielectric constant is needed in order to have lower EOT together with higher physical thickness which fulfils retention requirements. With this purpose we have studied nitrided Hf-silicates (k=15÷20) grown by Atomic Layer Deposition at 350ºC starting from HfCl4, SiCl4 and H2O. The attention has been focused on how the thermal stability of these materials is improved when nitrogen is inserted in the film by NH3 annealing. Their chemical properties have been studied by Time of Flight-Secondary Ion Mass Spectrometry and X-ray Photoemission Spectroscopy, while their morphological evolution has been followed by means of X-Ray Reflectivity, X-Ray Diffraction and Transmission Electron Microscopy.
What is the Essence of VFB Shifts in High-k Gate Stack?
Authors: Nabatame Toshihide , Iwamoto Kunihiko , Akiyama Koji , Nunoshige Yu , Ota Hiroyuki , Ohishi Tomoji , Toriumi Akira
Published: September 2007

Several origins for VFB shift have so far been discussed about metal/high-k/SiO2/Si structures and we focus on three topics such as bottom interface dipole at the high-k/interfacial layer (IL)-SiO2 interface, charge or dipole of bottom reaction layer in IL-SiO2, and dipole due to oxygen vacancy (Vo) in high-k layer by separating each type of these dipoles. We employed bi-layer high-k dielectrics such as HfO2/Al2O3/SiO2 and Al2O3/HfO2/SiO2 and demonstrated that the bottom interface dipole plays a critical role in determining the VFB shifts. We also show that VFB roll-off behavior in thinner EOT region can be associated with charge or dipole of the bottom reaction layer induced by re-oxidation at the IL-SiO2/Si interface. Finally, we show that Vo in HfO2 and Al2O3 dielectrics generated by HfxRu1-x alloy gates induces dipole at the high-k/IL-SiO2 bottom interface.
High Performance Gate-First pMISFET with TiN/HfSiON Gate Stacks Fabricated with PVD-Based In-Situ Method
Authors: Kawahara Takaaki , Nishida Yukio , Sakashita Shinsuke , Yugami Jiro , Kitano Naomu , Minami Takashi , Kosuda Motomu , Horie Shinya , Arimura Hiroaki , Shimura Takayoshi , Watanabe Heiji
Published: September 2007

We could obtain high performance gate-first pMISFET with TiN/HfSiON gate stacks fabricated with PVD-based in-situ method. High-quality Hf silicate gate dielectrics were formed by utilizing a solid phase interface reaction (SPIR) between a metal Hf layer and an SiO2 underlayer, and TiN electrodes were continuously grown on the gate dielectrics using a low-damage sputtering system without exposure to air.
Modeling and Simulation of Drain Current 1/f Noise in High-k Based n-MOSFETs
Authors: Srinivasan Purushothaman , Misra D.
Published: September 2007

This work summarizes the results of modeling and simulation of drain current low-frequency (1/f) noise in devices with Hf-based dielectrics as gate oxides. The proposed physics-based model is based on trap-assisted thermally activated tunneling in both the interfacial layer (IL) and the high-k layer. The model proposed considers not only the location of the traps in the oxide but also the energy level in the interfacial and the high-k layer. The critical factors which influence the drain current noise such as the tunneling time constant, and attenuation parameter are estimated. The estimated values are used to model drain current 1/f noise. The simulation results agree well with the experimental results, with errors in the acceptable margin levels. The results show the importance of interfacial layer and the temperature in determining the noise levels in high-k dielectrics.
The Development of New Membranes for Proton Exchange Membrane Fuel Cells
Authors: Emery Mike , Frey Matthew , Guerra Mike , Haugen Greg , Hintzer Klaus , Lochhaas Kai Helmut , Pham Phat , Pierpont Daniel , Schaberg Mark , Thaler Arne , Yandrasits Michael , Hamrock Steven
Published: September 2007

Recent work at 3M has focused on the development of solvent cast proton exchange membranes (PEM's) for use in PEM fuel cells. These new membranes are a perfluorinated sulfonic acids based on a low molecular weight perfluorinated monomer and they exhibit excellent mechanical properties and chemical stability and high ionic conductivity. The low molecular weight of the monomer allows membranes with equivalent weight as low as 800 g/mole to have good mechanical properties when hydrated. Stabilizing additives in these membranes have been shown to improve the oxidative stability in Fenton's tests. Physical property, conductivity and fuel cell tests have been performed. When incorporated into membrane electrode assemblies, these new membranes have provided excellent performance and a greater than 15-fold increase in durability under accelerated fuel cell test conditions, compared with similar commercial PEM's.
Crosslinker Effect on Fuel Cell Performance Characteristics of ETFE Based Radiation Grafted Membranes
Authors: Gubler Lorenz , Ben Youcef Hicham , Alkan Gürsel Selmiye , Wokaun Alexander , Scherer Guenther G.
Published: September 2007

Crosslinking of styrene grafted and sulfonated fuel cell membranes is essential to obtaining well-performing and durable membranes. The properties and fuel cell performance of radiation grafted membranes based on ETFE (25 micron) with different extent of crosslinking, using divinylbenzene (DVB) as co-monomer to styrene, was investigated. At high degrees of crosslinking, fuel cell performance was limited by the high ohmic resistance of the membrane, whereas at low degrees of crosslinking the membrane-electrode interface was of poor quality. Optimum performance was obtained at a degree of crosslinking corresponding to a styrene:DVB monomer ratio (v/v) in the grafting solution of 95:5.
Novel Sulfonated Polybenzimidazole by Direct Sulfonation in Sulfuric Acid
Authors: Peron Jennifer , Jones Deborah , Roziere Jacques
Published: September 2007

A novel type of polybenzimidazole that is soluble in polar organic solvents and in concentrated sulfuric acid has been functionalized for use as a fuel cell membrane via electrophilic substitution of hydrogen by sulfonic acid groups by direct sulfonation using sulfuric acid. The novel polybenzimidazole has three different types of site available for substitution, and the extent of their modification depends, for a given concentration of sulfuric acid, on the temperature of the reaction medium, and the duration of the reaction. The progress of the sulfonation reaction with reaction time and temperature has been monitored using 1H NMR. Polymers with ion exchange capacities up to ca. 4.2 meq/g are obtained, the properties of which depend upon the degree of sulfonation, but in all cases membranes show much more moderate water uptake and dimensional change than polyaromatic polymers of equivalent degrees of sulfonation.
Oxygen Reduction Reaction on Platinum/Tantalum Oxide Electrocatalysts for PEM Fuel Cells
Authors: Baturina Olga , Garsany Yannick , Zega Thomas , Stroud Rhonda , Swider-Lyons Karen
Published: September 2007

Three synthetic routes are evaluated to obtain highly dispersed platinum on tantalum oxide supported catalysts: a) deposition of platinum colloids on tantalum oxide followed by mechanical grinding with Vulcan carbon; b) deposition of tantalum oxide on Vulcan carbon, followed by the deposition of platinum colloids; and c) deposition of Pt colloids on Vulcan carbon, followed by deposition of tantalum oxide. Specific activities for oxygen reduction reaction at 0.9V are a factor of two higher for catalysts synthesized via preparation routes a and b compared to Pt/VC. In comparison, the activity of catalysts synthesized via route c is close to that of Pt/VC. Mass activities for the catalysts possessing high specific activities are lower than for Pt/VC due to their low electrochemically available platinum surface area.
Study on Degradation of the Pt-Ru Anode of PEFC for Residential Application (2): Analyses of the MEAs Degraded in the Anode Performance
Authors: Yamazaki Osamu , Oomori Yasuharu , Shintaku Hideki , Tabata Takeshi
Published: September 2007

Significant decrease in the voltage and increase in H2 gain were observed after the low current density operation. However, recovery in voltage and decrease in H2 gain were also observed by the dry treatment. The impedance of degraded MEA just after the low current density operation increased at the low frequency region in CO(10ppm)/H2(balance). On the other hand, the impedance of MEA that the H2 gain was increased by long term operation for more than 20,000 h was increased at higher frequency region in CO(10ppm)/H2(balance). It was concluded that the increase of impedance was caused by the flooding in the anode in the first case, and by the essential degradation by Ru dissolution from anode catalyst in the later case.
Anode Overpotential at Low Pt Loadings for Pure H2
Authors: Kinoshita Shinji
Published: September 2007

The cell performances of MEAs with low anode platinum loading were demonstrated. The MEA with anode Pt loading of 0.02 mg/cm2 had negligible voltage loss at current densities up to 2 A/cm2. MEAs having anode Pt loadings below 0.01 mg/cm2 gave higher voltage degradation rates in durability testing with load cycles. The results will be useful to determine the anode Pt loading to maximize the performance of MEAs within the required costs for commercial applications.
Synthesis and Conductivity of Indium-Doped Tin Pyrophosphates
Authors: Einsla Melinda L. , Mukundan R. , Brosha Eric L. , Garzon F. H.
Published: September 2007

We have synthesized indium-doped tin pyrophosphates as high-temperature anhydrous proton conductors. The ratio of tin to indium was varied using two different synthetic methods. The first is a high-temperature reaction in which a paste containing the reactants in excess phosphoric acid was heated for various amounts of time at various temperatures. The second method is a solution precipitation procedure followed by calcination, which offers several advantages over traditional synthetic techniques. These advantages include better stoichiometric control, lower temperature requirements, and chemically uniform products. Several phosphate sources were investigated, including phosphoric acid, pyrophosphoric acid, and potassium pyrophosphate. The resulting indium-doped tin pyrophosphates had good proton conductivity over a wide temperature range with no humidification.
A PEM Fuel Cell based on Carbon-Fiber Electrodes Modified with Platinum Nanoparticles Encapsulated in PAMAM Dendrimers
Authors: Ledesma-Garcia Janet , Escalante Ismailia L. , Barbosa Romeli , Chapman Thomas , Arriaga Luis G. , Godínez Luis
Published: September 2007

This report describes the construction and testing of fuel cells based on carbon-fiber-paper electrodes that were first functionalized in acid media by anodic pretreatment and then modified with platinum nanoparticles encapsulated in hydroxyl-terminated dendrimers (G4OHPt). Scanning the potential of the functionalized carbon-fiber electrodes in a solution containing the dendrimer-encapsulated nanoparticles immobilizes the material on the carbon surface. Previous studies have shown the capacity of the supported nanoparticles to catalyze the oxygen-reduction reaction and suggested some promising approaches that such electrodes offer for the development of more efficient fuel cells. Here we present preliminary results on the performance of experimental fuel cells based on nanoparticle-modified carbon-fiber electrodes.
Formation Of Low Frequency Inductive Loops In Polymer Electrolyte Fuel Cell (PEFC) Impedance Spectra Under Sub-Saturated Conditions
Authors: Schneider Ingo A. , Bayer Michael H. , Boillat Pierre , Wokaun Alexander , Scherer Guenther G.
Published: September 2007

The impact of water formation and accumulation along the flow channels on the ac impedance response of a H2/O2-PEFC operated under sub-saturated conditions was investigated. The first experimental results, as presented and discussed in this work, show that a low frequency capacitive and inductive behaviour observed in the spectra is consistent with the experimentally observed characteristic local ac response to upstream processes along the flow channels. It is shown that sinusoidal oscillations in the water concentration build up along the flow field and cause a sinusoidal changing membrane resistance in downstream parts of the cell. This effect becomes dominating at lower frequencies, where the inductive loop occurs in the spectrum. In the light of this result, the occurence of the low frequency inductive loop under sub-saturated conditions is indicative of a limitation of the local cell performance by formation and accumulation of water along the flow channels.