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Proceedings Papers
ISTFA2022, ISTFA 2022: Conference Proceedings from the 48th International Symposium for Testing and Failure Analysis, 74-77, October 30–November 3, 2022,
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Non-planar semiconductor devices, such as vertical fin-based field-effect transistor (FinFET) devices have been developed that include multiple vertical fins serving as conducting channel regions to enable larger effective conduction width in a small layout area. However, as circuits are scaled to smaller dimensions, it has become increasingly difficult to improve the performance of FinFET devices. Stacked nanosheet FETs have been developed to further enable larger effective conduction width in a given small layout area while enabling gate length scaling. Nanosheet (NS) FET devices have attracted attention as a candidate to replace FinFET technology at the 5 nm technology node and beyond due to their excellent electrostatics and short channel control. The use of silicon-germanium for the channel material has been explored as a major technology element for FinFET CMOS technology, and the performance benefits of Si-Ge channel over silicon channel have been demonstrated. Compared with conventional FinFET, stacked gate-all-around (GAA) NS CMOS shows higher electron mobility for nFET but lower hole mobility for pFET due to its unique device architecture and carrier transport direction. To improve pFET performance, SiGe NS is proposed as the pFET channel material. However, introducing and maintaining strain in the SiGe GAA NS channel is challenging but important for improving carrier transport. It is critical to understand the strain distribution in the advanced 3D nanosheet FET structures. This paper describes the use of advanced transmission electron microscopy (TEM) techniques to investigate the strain distribution in strained SiGe channel NS pFET through Si channel trimming and selective Si1-xGex epitaxial growth. A stacked GAA NS pFET was fabricated from compressively strained Si1-xGex channel with good crystallinity and high uniaxial compressive stress of ~1 GPa. From lattice deformation maps with a nanometer spatial resolution obtained by TEM techniques, the authors demonstrate that nano-beam precession electron diffraction techniques can be used to investigate the local strain distribution of the stacked GAA NS pFET devices with high precision, and thus help to optimize the integration process and strain engineering for pFET device performance enhancement for the next generation of CMOS logic in GAA NS technology.
Proceedings Papers
ISTFA2021, ISTFA 2021: Conference Proceedings from the 47th International Symposium for Testing and Failure Analysis, 34-39, October 31–November 4, 2021,
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There are several variants of artificial intelligence (AI) hardware structures that are under study by the semiconductor industry for potential use in complementary metal–oxide–semiconductor (CMOS) designs. This paper discusses some of the failure analysis challenges that have appeared in discrete test structures and test arrays developed as part of an exploratory phase-change memory (PCM) program at IBM's Albany AI Hardware Research Center.
Proceedings Papers
ISTFA2021, ISTFA 2021: Conference Proceedings from the 47th International Symposium for Testing and Failure Analysis, 206-210, October 31–November 4, 2021,
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In this work, we investigate mushroom type phase-change material (PCM) memory cells based on Ge 2 Sb 2 Te 5 . We use low-angle annular dark field (LAADF) STEM imaging and energy dispersive X-ray spectroscopy (EDX) to study changes in microstructure and elemental distributions in the PCM cells before and after SET and RESET conditions. We describe the microscope settings required to reveal the amorphous dome in the RESET state and present an application example involving the failure analysis of a PCM test array made with devices fabricated at IBM’s Albany AI Hardware Research Center.
Proceedings Papers
ISTFA2020, ISTFA 2020: Papers Accepted for the Planned 46th International Symposium for Testing and Failure Analysis, 53-56, November 15–19, 2020,
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The continuously growing demands in high-density memories drive the rapid development of advanced memory technologies. In this work, we investigate the HfOx-based resistive switching memory (ReRAM) stack structure at nanoscale by high resolution TEM (HRTEM) and energy dispersive X-ray spectroscopy (EDX) before and after the forming process. Two identical ReRAM devices under different electrical test conditions are investigated. For the ReRAM device tested under a regular voltage bias, material redistribution and better bottom electrode contact are observed. In contrast, for the ReRAM device tested under an opposite voltage bias, different microstructure change occurs. Finite element simulations are performed to study the temperature distributions of the ReRAM cell with filaments formed at various locations relative to the bottom electrode. The applied electric field as well as the thermal heat are the driving forces for the microstructure and chemical modifications of the bottom electrode in ReRAM deceives.
Proceedings Papers
ITSC 2017, Thermal Spray 2017: Proceedings from the International Thermal Spray Conference, 843-848, June 7–9, 2017,
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Thermal insulation performance is a measurement of the thermal protection offered by the thermal barrier coatings (TBCs) to the substrate, therefore, it is essentially important to compare different double ceramic layer (DCL) TBCs on the premise of the same thermal resistance. In this study, a series of LZO/YSZ DCL-TBCs, with the equivalent thermal insulation to 500 µm thick YSZ TBCs, were prepared, and their lifetimes were evaluated by thermal gradient cyclic test at the top coat surface temperature of 1300°C. Result show that, the lifetime of DCL-TBCs was more than doubled compared to 500 µm thick YSZ TBCs, when 100µm thick YSZ coating was substituted by LZO coating. In addition, the lifetime of DCL-TBCs decreased with the increase of LZO substitutional ratio. X-ray diffraction analysis revealed that LZO maintains the pyrochlore structure after thermal cyclic test. Microstructure examination demonstrated that, with the increase of LZO substitutional ratio, the delamination position transferred from near top/bond coating interface to near LZO/YSZ interface and finally to the inside of LZO coating. Therefore, this study would shed light to further coating structure optimization towards the next generation advanced DCL-TBCs.
Proceedings Papers
ITSC 2017, Thermal Spray 2017: Proceedings from the International Thermal Spray Conference, 849-854, June 7–9, 2017,
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The non-parabolic isothermal oxidation kinetics of low pressure plasma sprayed MCrAlY bond coat was investigated. To qualitatively explain the abnormal growth phenomenon of thermally grown oxides (TGO), the changes that occurred to their microstructure during the oxidation process were studied. Based on these observations, a modified model was developed to understand and quantitatively predict the non-parabolic oxidation and growth kinetics of TGO. This modified model, which fits well with experimental results, provides a novel method to quantitatively predict the long-term growth behaviour of TGO, and thereby benefits the development of long-life and highly reliable thermal barrier coatings.
Proceedings Papers
ITSC 2017, Thermal Spray 2017: Proceedings from the International Thermal Spray Conference, 861-866, June 7–9, 2017,
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Thermal cycle lifetime is essentially important to the application of thermal barrier coatings (TBCs) on the premise of the same thermal resistance. In this study, equivalent thermal insulation conception is introduced to the design of dense vertical crack (DVC) structured TBCs and the lamellar structured TBCs, to fairly compare the lifetime of TBCs with different structure. DVC-structured TBCs with the equivalent thermal insulation to lamellar YSZ TBCs were prepared, and their lifetimes were evaluated by thermal gradient cyclic test. Cross-sectional morphology and phase constitution before and after failure were examined by scanning electron microscope and X-ray diffraction, respectively. The failure mode was analysed. This study would shed light to further coating structure optimization.
Proceedings Papers
ITSC 2017, Thermal Spray 2017: Proceedings from the International Thermal Spray Conference, 899-904, June 7–9, 2017,
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Inter-lamellae bonding within thermal sprayed coatings is one of the most important factors influencing the properties and performance of coatings. It has been revealed that there exists a critical bonding temperature for a molten ceramic splat to form the bonding to the same splat surface. The erosion behaviors of thermal sprayed coatings are significantly influenced by the interface bonding between lamellae. In this study, the erosion behavior of plasma-sprayed TiO 2 , Al 2 O 3 and YSZ coatings deposited at different deposition temperatures was investigated. The cross section of plasma sprayed coatings was characterized by the scanning electron microscope. It was revealed that the coatings deposited at room temperature exhibit a typical lamellar structure with numerous unbonded interfaces, whereas the coatings prepared at the temperature above the critical bonding temperature present a dense structure with well bonded lamellae. The erosion rate significantly decreases with the improvement of interface bonding. In addition, the erosion mechanisms of the conventional coatings and the lamellae well bonded coatings were further discussed. The unbonded interfaces act as precracks accelerating the erosion of plasma-sprayed coatings. Thus, controlling inter-lamellae bonding based on the critical bonding temperature is conducive to the improvement of erosion resistance of plasma-sprayed ceramic coatings.
Proceedings Papers
ITSC 2017, Thermal Spray 2017: Proceedings from the International Thermal Spray Conference, 905-910, June 7–9, 2017,
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In the present study, a novel and practical method, white light interference, was proposed to characterize the lamellar pores covered by thermally sprayed YSZ and LZ splats. In this method, only an ordinary optical microscopy (OM) was employed. Colorful Newton rings and parabolic shapes of the lamellar pores were widely observed by OM. The crack spacing and the shapes of the lamellar pores captured by OM were well consistent with those by scanning electron microscopy (SEM) and focus ion beam (FIB). Besides, mechanical analyses were carried out and the results were well consistent with those by OM. Most importantly, the essential fact that the lamellar pores resulted from transverse cracking/delamination in thermal sprayings was highly elaborated.
Proceedings Papers
The Influence of Deposition Temperature and Thermal Conductivity of the Substrate on Splat Formation
ITSC 2017, Thermal Spray 2017: Proceedings from the International Thermal Spray Conference, 956-962, June 7–9, 2017,
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Ni20Cr splats were sprayed onto polished substrates at different preheating temperatures in an argon atmosphere by Low Pressure Plasma Spray to reveal the dominating factor on the effective interface bonding formation. The splat morphology, microstructure and splat-substrate interface bonding were characterized by SEM and EBSD. The interface for examination of typical splats was prepared by FIB. Disk splats were obtained on AISI 304 stainless steel substrates preheated to temperatures of 100 °C (cooling from 350 °C), 350 and 550 °C. Moreover, typical distinct two-zone microstructure feature was observed on the splat surface by SEM and EBSD, including central coarse grain and marginal fine grain. When the preheating temperature was higher than 350 °C, effective bonding formed only in the entire central coarse zone, whereas no effective bonding was observed in the fine grain zone. By using glass, copper, nickel and 304 SS as substrates, it was found that increasing thermal conductivity of metallic substrates has little effect on splat diameter and morphology and however decreased the area fraction of central coarse grain zone. It was revealed that the melt/substrate interface temperature plays a crucial role on the interface bonding formation.
Proceedings Papers
ITSC2016, Thermal Spray 2016: Proceedings from the International Thermal Spray Conference, 68-72, May 10–12, 2016,
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In this study, superhydrophobic samaria-doped ceria coatings are produced by plasma spray physical vapor deposition (PS-PVD) followed by fluorination treatment. Samples are sprayed at distances of 300, 400, and 500 mm in order to obtain surfaces with different morphology. SEM examination shows that the surfaces have a hierarchical structure with island-like features consisting of nanoparticles, the size of which is shown to influence sliding behavior. The superhydrophobic coating surfaces also exhibited good stability in repeated adhesive-tape tear tests.
Proceedings Papers
ITSC2016, Thermal Spray 2016: Proceedings from the International Thermal Spray Conference, 641-647, May 10–12, 2016,
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This study investigates the correlation between thermal barrier coating (TBC) lifetime and thermally grown oxide (TGO) layer thickness. YSZ TBCs were deposited by atmospheric plasma spraying on Ni-base substrates and subjected to burner cycling tests with a thermal gradient and isothermal furnace testing. Both tests revealed that thermal cycling lifetime decreases with increasing TGO thickness, following a power law function, and for a critical TGO thickness of 5-6 μm, the failure mode changes from cracking within the YSZ layer to interface cracking around the TGO. Although either test can be used to evaluate TBC performance, burner cycling tests are better suited for evaluating ceramic topcoats, while furnace cycling test results integrate the effects of bond coat properties, especially oxidation resistance, as well as ceramic topcoat cracking resistance. The two tests can thus be used together to assess the factors that control TBC failure.
Proceedings Papers
ITSC2016, Thermal Spray 2016: Proceedings from the International Thermal Spray Conference, 765-770, May 10–12, 2016,
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One way to reduce plasma jet velocity and prolong the dwell time of spray particles in the jet is to enlarge the orifice of the torch nozzle. In this study, normal and modified nozzles are used to deposit YSZ particles on ceramic and superalloy substrates by plasma spray-physical vapor deposition (PS-PVD). The modified nozzle is shown to increase the evaporation of YSZ particles and thus the quantity of Zr atoms and Zr 1+ ions in the plasma jet, which allows columnar structured coatings to be realized at higher deposition rates using a conventional 80 kW plasma spray system. The columnar ceramic coatings are also shown to have good conformity on cold-sprayed MCrAlY bond coats with high surface roughness.
Proceedings Papers
ITSC2016, Thermal Spray 2016: Proceedings from the International Thermal Spray Conference, 846-851, May 10–12, 2016,
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In this work, liquid plasma spraying is used to deposit composite coatings for potential use as cathodes in intermediate-temperature solid oxide fuel cells. A suspension containing well-distributed Gd-doped ceria (GDC) nanoparticles in a lanthanum strontium cobalt ferrite precursor solution was used as the feedstock, and GDC concentration was varied to study its effect on phase composition, microstructure, surface morphology, and electrochemical performance. The results are presented and discussed.
Proceedings Papers
ITSC2016, Thermal Spray 2016: Proceedings from the International Thermal Spray Conference, 1046-1051, May 10–12, 2016,
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This study demonstrates a novel method for improving the corrosion resistance of cold sprayed Al6061 coatings. Large stainless steel particles were added to a commercial Al6061 powder and the mixture was deposited on Mg alloy AZ31B substrates using nitrogen gas at low working pressure and temperature. It is shown that the stainless steel particles had a shot-peening effect, thus increasing the density as well as the corrosion resistance of Al6061 coatings. SEM examination showed that no stainless steel particles were incorporated in the coating.
Proceedings Papers
ITSC2016, Thermal Spray 2016: Proceedings from the International Thermal Spray Conference, 1052-1058, May 10–12, 2016,
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Interparticle bonding is considered the most important factor in cold sprayed coatings, determining mechanical properties as well as physical and chemical behaviors. In this study, a Cu feedstock with low oxygen content is deposited with relatively high spray pressure and temperature in order to improve interparticle bonding and obtain a coating cohesive strength. Mechanical bonding between deposited particles is deduced from fracture morphology and the deformation behavior of Cu particles is simulated by finite element analysis.
Proceedings Papers
ITSC2016, Thermal Spray 2016: Proceedings from the International Thermal Spray Conference, 1138-1144, May 10–12, 2016,
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In this study, stainless steel splats were deposited on preheated stainless steel substrates with oxide scales of different thickness in inert low-pressure plasma spay (LPPS) conditions to examine the effect of in-situ oxidation of prior splats on the morphology and bonding of subsequently formed splats. Splat-substrate interface cross-sections were prepared by focus-ion-beam milling. Splat morphology and bonding state with the substrate were characterized by SEM. The results show that with oxide films up to 35 nm thick, disk-type splats are deposited that bond well to the substrate except in the periphery region. As oxide films become thicker (100 nm) and present a surface with micro-scale roughness, splats take on a finger-like shape with poor bonding at the interface.
Proceedings Papers
ITSC 2015, Thermal Spray 2015: Proceedings from the International Thermal Spray Conference, 634-640, May 11–14, 2015,
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Transparent hydrophobic materials have broad application prospects in industry and daily life due to its transparent and super-hydrophobic characteristics, while its performance will be significantly influenced by the materials and its surface morphology. Hydrophobicity and transparency are competitive properties from the viewpoint of surface roughness. However, there are still a lot of problems to be solved to satisfy hydrophobicity and transparency simultaneously in the prepared surface. A novel and simple method to fabricate transparent hydrophobic surface is introduced in the present paper. Micron and sub-micron mixed Al 2 O 3 powders were deposited on the glass and plastic substrate by vacuum cold spray. The coatings were modified by 1,1,2,2- Tetrahydroperfluorodecyltrimethoxysilane (FAS) to reduce the surface energy. The surface morphology was characterized by scanning electron microscopy (SEM) and 3D laser microscopy (LSM). The transmittance of the coating was also investigated. The results show that the as-sprayed surfaces exhibit submicron structure. After FAS absorbing treatment, the contact angle of water droplets on the coatings ranged from 108° to 136° depending on the local surface morphology, and the transmittance of Al 2 O 3 coatings are all above 80% in the range of visible light.
Proceedings Papers
ITSC 2015, Thermal Spray 2015: Proceedings from the International Thermal Spray Conference, 841-845, May 11–14, 2015,
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A new method to fabricate micro-nano scaled surface with super-hydrophobicity is introduced in the present paper. Micro-nano hierarchical structure coatings based on silica (SiO 2 ) micron particles were successfully deposited on the stainless steel substrates by high-velocity oxygen fuel (HVOF) spraying which were modified by 1,1,2,2- Tetrahydroperfluorodecyltrimethoxysilane (FAS) to reduce surface energy. The influences of the HVOF process parameters on the wettability of the coatings were investigated. The coatings were characterized by scanning electron microscopy (SEM), 3D laser microscopy (LSM), and Fourier transform infrared spectrometer (FTIR). The results show that the as-sprayed surfaces exhibit micro-nano hierarchical structure. The water droplets are strongly adhesive to the as-sprayed surface, while by FAS absorbing treatment, the surfaces exhibit super-hydrophobicity, whose contact angle with water droplets are as high as 150°, and the water droplets tend to roll on the surface with extremely low adhesion with a sliding angle of 3°
Proceedings Papers
ITSC2014, Thermal Spray 2014: Proceedings from the International Thermal Spray Conference, 268-272, May 21–23, 2014,
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In this study, YSZ coatings are deposited by plasma spray-physical vapor deposition using a shroud to limit expansion of the plasma jet and increase its heating ability. Optical emission spectroscopy shows that the shroud significantly increases the evaporation of YSZ particles in the jet, resulting in coatings with a hybrid columnar structure. SEM examination of coating surfaces and cross-sections reveal micro and nanoscale features and, in each case, the mechanisms of formation are discussed.
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