Influence of thickness on nanomechanical behavior of Black Diamond™ low dielectric thin films for interconnect and packaging applications

In the present study, we have investigated the thickness dependence of mechanical properties of the Black Diamond? (SiOC:H, BD, Low-k) films, which are of great interest in current Cu/low-k Back End of the Line (BEOL) interconnect/packaging technologies. For this investigation the BD thin films of six different thicknesses 100, 300, 500, 700, 1,000 and 1,200 nm were deposited on the 8″ Si wafer by using plasma enhanced chemical vapor deposition (PECVD) technique. Nanoindentation and nanoscratch tests of the BD films were performed by using the Nano Indenter^® XP (MTS Corp. USA). In nanoindentation testing of the BD films, significant differences in the elastic modulus of the BD films were observed. In nanoscratch testing, it is found that the critical load (Lc) and scratch width increases as the thickness of the film increases. Cross-sectional analysis of residual nanoindentation impressions was carried out using atomic force microscopy (AFM) to study the deformation behavior. The nanoindentation and nanoscratch responses of the BD thin films of six different thicknesses are different and they are expected mainly due to the molecular reorganization in thin/ultra thin films.     

Dishing and nitride erosion of STI-CMP for different integration schemes

In this paper, we investigate the effects of integration schemes on the STI-CMP performance of two polishers, as well as the influence of consumables and process parameters. The experiment was based on both the blanket-oxide wafers and the patterned wafers processed using 0.18 μm technology. The polishing capability was evaluated, based on the results collected using metrology tools such as Opti-probe, Tencor profiler; atomic force microscope (AFM), and x-ray-scanning electron microscopy (X-SEM) analysis.     

Enhancement of adhesion strength of Cu layer with low dielectric constant SiC:H liners in Cu interconnects

One of the primary candidates for the liner/etch stop layer in damascene process is silicon nitride (Si₃N₄). However, silicon nitride has a high dielectric constant of 7.0. To reduce the effective dielectric constant in Copper (Cu) damascene structure, dielectric SiC:H (prepared by plasma enhanced chemical vapor deposition (PECVD) using trimethylsilane source) as the Cu diffusion barrier was studied. The dielectric constant of SiC:H used is 4.2. A systematic study was made on the properties of liner material and electro-chemically plated (ECP) Cu to enhance the adhesion strength in Cu/low-dielectric constant (k) multilevel interconnects. Though the effects of as Si₃N₄ the liner have been much studied in the past, less is known about the relation between adhesion strength of ECP Cu layer and physical vapor deposited (PVD) Cu seeds, with seed thickness below 1000 Å. The annealing of Cu seed layer was carried out at 200 °C in N₂ ambient for 30 min was carried out to study the impact on adhesion strength and the microstructure evolution on the adhesion between ECP Cu and its barrier layer. In the study, our claim that SiC:H barrier/etch stop layer is essential for replacing conventional Si₃N₄ layer in enhancing adhesion strength and interfacial bonding between Cu/dielectric interconnects.     

Effect of succinonitrile and nano-hydroxyapatite on ionic conductivity and interfacial stability of polyether-based plasticized nanocomposite polymer electrolytes (PNCSPE)

A series of novel plasticized nanocomposite solid polymer electrolytes (PNCSPE) consisting of polyethylene oxide as polymer host, lithium bisoxalatoborate as salt with different weight ratios of succinonitrile and nano-hydroxyapatite was prepared by membrane hot-press technique. The electrical property of PNCSPE was investigated by AC impedance analysis. The migration of lithium ion in the polymer matrix was confirmed from cyclic voltammetry study. The incorporation of different compositions of filler and plasticizer in the polymer matrix significantly enhanced the amorphous nature resulted in increase in ionic conductivity of PNCSPE. The maximum ionic conductivity was found to be in the order of 10^?3.1 S/cm.     

Ge-Rich (70%) SiGe Nanowire MOSFET Fabricated Using Pattern-Dependent Ge-Condensation Technique

A top-down approach of forming SiGe-nanowire (SGNW) MOSFET, with Ge concentration modulated along the source/drain (Si_0.7Ge_0.3) to channel (Si_0.3Ge_0.7) regions, is presented. Fabricated by utilizing a pattern-size-dependent Ge-condensation technique, the SGNW heterostructure PMOS device exhibits 4.5times enhancement in the drive current and transconductance (G_m) as compared to the homojunction planar device (Si_0.7Ge_0.3). This large enhancement can be attributed to several factors including Omega-gated nanowire structure, enhanced hole injection efficiency (due to valence band offset), and improved hole mobility (due to compressive strain and Ge enrichment in the nanowire channel).     

Enhanced photocatalytic performance of CuFeO2-ZnO heterostructures for methylene blue degradation under sunlight

One of the strategies to overcome the drawbacks of fast charge recombination of a photocatalyst is to develop semiconductor heterostructures. Herein, we report a two-step precipitation-hydrothermal process to create CuFeO₂-ZnO heterostructures with different weight percentages of CuFeO₂ (0.5, 1, 5, and 10%). Though X-ray diffraction detected the presence of CuFeO₂ on ZnO above 5%, Raman spectroscopy could reveal the presence of CuFeO₂ phase as low as 0.5 wt%. For all of the compositions, the bandgap of ZnO did not vary (3.15 eV) on forming heterostructures with CuFeO₂. The oxidation of methylene blue under sunlight was used to determine the photocatalytic performance of the heterostructures. In comparison to pure ZnO and CuFeO₂, CuFeO₂-ZnO heterostructures exhibited a better photocatalytic efficiency. Overall, 5 wt% CuFeO₂ on ZnO showed 100% degradation with a rate constant of 0.272?±?0.002 min^?1, which is 16 times faster than ZnO. Time-resolved photoluminescence analysis indicated a higher lifespan of charge carriers in the 5wt% CuFeO₂-ZnO heterostructure (32.3 ns) than that of CuFeO₂ (0.85 ns) and ZnO (27.6 ns). The Mott–Schottky flat band potentials of ZnO and CuFeO₂ was determined to be -0.82 and 1.17 eV, respectively, revealing the presence of Type I heterostructures. The heterostructures also showed outstanding recyclability, with a degradation rate of 97% even after four cycles. The current study shows the significance of forming p-type CuFeO₂ and n-type ZnO heterostructures for enhanced photocatalysis.

     

Hydrothermally synthesized ZnO and Z-rGO nanorods: Effect of post-annealing temperature and rGO incorporation on hydrogen sensing

Journal of Materials Science: Materials in Electronics - In this work, hydrogen-sensing characteristics of zinc oxide nanorods and reduced graphene oxide-incorporated zinc oxide nanorods are...     

Cu(II), Co(II) and Ni(II) Complexes Installed on Functionalized Silica Surface for Hydrogen Peroxide Assisted Cyclohexane Oxidation

In this work, Cu(II), Co(II) and Ni(II) complexes of the Schiff base ((S,E)-2-(3,4-dimethoxybenzylideneamino)-3-(1H-imidazol-4-yl)propionic acid) were synthesized and subsequently anchored onto amine functionalized silica. They were characterized by FT-IR, UV–vis., ²⁹Si NMR, TG-DTG, ESR, FE-SEM and AFM techniques, and employed as catalysts in cyclohexane oxidation using hydrogen peroxide oxidant. Silica supported Cu(II) catalyst was shown the highest catalytic activity (70%) than rest of the catalysts used. On the other hand, all the complexes were selective as they yield only cyclohexanol and cyclohexanone. Silica supported catalysts were maintained their catalytic activity over five successive catalytic run. As these catalysts are selective, reusable and functioning well with hydrogen peroxide, they could design the environment friendly catalytic system for effective cyclohexane oxidation.     

Comparison of Industrial Scale Ethanol Production from a Palmyrah‐Based Carbon Source by Commercial Yeast and a Mixed Culture from Palmyrah Toddy

Palmyrah (Borassus flabellifer) based products were used as an alternative carbon source for industrial scale ethanol production. The fermentation medium was enriched with spent wash obtained from a distillation column. The performance of a commercially available baker's yeast in the media was compared with a ‘palmyrah toddy mixed culture’ where the organisms were obtained from the sedimentation of palmyrah toddy. In a laboratory scale study, the ethanol produced from a palmyrah fruit pulp extract, diluted with distilled water, was 16.5 gL^?1 (36 h) and 13.0 gL^?1 (48 h) with ‘palmyrah toddy mixed culture’ and baker's yeast respectively. The ‘palmyrah toddy mixed culture’ performed better than the baker's yeast with palmyrah fruit pulp extract, diluted either with distilled water or spent wash. Among the different palmyrah based carbon sources, both cultures preferred molasses diluted with spent wash and both performed best in the medium containing the spent wash supplemented with sucrose. In a 5,000 L industrial scale fermentation of 20° Brix molasses supplemented with 10 gL^?1 ammonium sulphate, 72 gL^?1 and 65 gL^?1 ethanol was produced by the ‘palmyrah toddy mixed culture’ (72 h) and the baker's yeast (90 h) respectively. As the performance of the ‘palmyrah toddy mixed culture’ was better than that of the baker's yeast, the former was selected for the industrial scale studies of molasses fermentation media diluted with spent wash. In these studies the temperature reached 42°C by 36 h and resultant cell death was observed. However ethanol production was higher and more rapid in the molasses diluted with spent wash, rather than in the molasses diluted with tap water and supplemented with (NH₄)₂SO₄. Cell recycle operation obviated the interruption in fermentation caused by temperature induced cell death and increased rates and efficiency of ethanol production were observed.     

Large- and very-large-scale motions in channel and boundary-layer flows

Large-scale motions (LSMs; having wavelengths up to 2-3 pipe radii) and very-LSMs (having wavelengths more than 3 pipe radii) have been shown to carry more than half of the kinetic energy and Reynolds shear stress in a fully developed pipe flow. Studies using essentially the same methods of measurement and analysis have been extended to channel and zero-pressure-gradient boundary-layer flows to determine whether large structures appear in these canonical wall flows and how their properties compare with that of the pipe flow. The very large scales, especially those of the boundary layer, are shorter than the corresponding scales in the pipe flow, but otherwise share a common behaviour, suggesting that they arise from similar mechanism(s) aside from the modifying influences of the outer geometries. Spectra of the net force due to the Reynolds shear stress in the channel and boundary layer flows are similar to those in the pipe flow. They show that the very-large-scale and main turbulent motions act to decelerate the flow in the region above the maximum of the Reynolds shear stress.