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Three-dimensional ordered macroporous Ni films, known as Ni inverse opals, are fabricated via a template approach in which polystyrene (PS) microspheres (820 nm in diameter) are assembled in closely-packed colloidal crystals via a vertical electrophoresis process, followed by electroplating of Ni into the interstitial voids within the colloidal crystals and the selective removal of PS microspheres. To improve its mechanical strength, a conformal Ni-Co layer (45 ~ 64 nm) is electrodeposited on the skeletons of the Ni inverse opals by cyclic voltammetry. After coating, from nano-indentation tests, the hardness and reduced elastic modulus are enhanced considerably (172 ~ 220% for hardness; 72 ~ 79% for reduced elastic modulus), as compared to those of pristine inverse opals. After an annealing treatment for the interdiffusion of Ni and Co, the sample reveals an even stronger hardness. X-ray diffraction patterns indicate that the finite thickness of the inverse opals skeletons induces preferential growth of the (111) plane. In short, a combined effect of solid solution alloying, thickening of inverse opals skeletons for greater load bearing, and a predominant (111) plane is responsible for the improved mechanical strength of the Ni inverse opals. [ABSTRACT FROM AUTHOR]

To inhibit the detrimental diffusion of copper into silicon devices, an effective barrier is strongly demanded. In this study, copper(rhenium) alloy films were successfully electroless- and electroplated on silicon substrates for self-forming an ultrathin rhenium barrier layer. In pure copper films, the interdiffusion of copper and silicon already occurred at 400°C, forming silicides and increasing the electrical resistivity of the films. In comparison, not any silicide formation was observed in the electroless- and electroplated copper(rhenium) alloy films with minor incorporations of rhenium for 0.10 and 0.39 at% until 600 and 500°C, respectively, attributed to the prior segregation of rhenium and the self-formation of rhenium barrier layer at the copper/silicon interface at 400°C. A zero solubility of rhenium in copper and a small solubility in palladium catalysts facilitate the separation of rhenium from copper. The kinetics of rhenium segregation follows uphill diffusion, and the diffusivity of rhenium in copper at 400°C is estimated to be 1.5 x 10-17 cm²/s. [ABSTRACT FROM AUTHOR]

In this study, very simple periodic cathodic vacuum arc deposition was conducted to prepare multilayered structures of diamond-like carbon films with reduced surface roughness and enhanced mechanical properties compared to conventional unfiltered single-layered films. The roughness of single-layered diamond-like carbon films significantly increased from 23 to 104 nm with increasing thickness from 100 to 800 nm due to the droplet formation in plasma atmosphere. By introducing periodic deposition, the roughness of the multilayered structures with a thickness of 400 nm was reduced from 75 to 37 nm, associated with a much smaller number of surface particles. The hardness of the multilayered structures was enhanced from 27 to 34 GPa, and the interface adhesion was increased from 2.73 to 3.63 J/m2. The single- and multilayered films showed a similar amorphous structure with slightly varied ID/IG ratios from 0.9 to 0.6. The periodic deposition process was the dominant factor for the reduced roughness and enhanced mechanical properties of the unfiltered films. [ABSTRACT FROM AUTHOR]

In this study, hydroxyapatites were deposited on surface modified carbon fibers using a simulated body fluid; different amounts of COOH functional group were formed on the fiber surfaces by different degrees of KOH pretreatment. The effect of the surface functional group on the growth features of the hydroxyapatite crystals was analyzed, and the detailed stacking and structural correlations of the grown crystals to the substrate carbon fibers were examined to realize the mineralization mechanism, It was observed that hydroxyapatite nanocrystallites longitudinally constructed a crystal chain along [211] direction; several aligned crystal chains were then bundled to form a spindle structure which ultimately composed differently featured coatings. A mild KOH pretreatment created a small amount of functional group that activated few sites for hydroxyapatite nucleation compliant to the COOH bond structure, yielding a horizontally oriented olive Structure under an orientation correlation HAP [112] or [211]//C [100]. A severer treatment induced more nucleation sites; attributed to the repulsion between the close COO- ligands, the bond structure was bent, leading to the radially aligned and ball-featured growth of hydroxyapatites with a different correlation HAP [1121 or [211] //C [002]. [ABSTRACT FROM AUTHOR]

In this study, (AICrTaTiZr)N0.7 and (AICrTaTiZr)N1 films with quinary metallic elements were developed as diffusion barrier materials for Cu interconnects. To improve the interface adhesion to Cu, an AICrTaTiZr buffer layer was deposited on the barriers to form (AICrTaTiZr)N0.7/AICrTaTiZr and (AICrTaTiZr)N1/A1CrTaTiZr bilayer structures. The as-deposited AlCrTaTiZr and (AICrTaTiZr)N0.7 films were amorphous structures, and (AICrTaTiZr)N1 possessed a nanocomposite structure. After annealing at 800°C, although Cu penetrated into the AICrTaTiZr buffer layer, the diffusion of Cu was retarded by the (AICrTaTiZr)N0.7 and (AICrTaTiZr)N1 barriers. During annealing at 900°C, the interdiffusion of Si and Cu occurred through the (AICrTaTiZr)N0.7/AICrTaTiZr bilayer, and Cu silicides formed. However, the (AlCrTaTiZr)N1 /AICrTaTiZr bilayer remained stable. Neither the interdiffusion of Cu and Si through the (AICrTaTiZr)N1/AlCrTaTiZr bilayer nor the silicide formation was identified, indicating the high diffusion resistance of the bilayer structure. [ABSTRACT FROM AUTHOR]

In this study, TiVCr and T1VCrZrY films were deposited on Si substrates by magnetron sputtering with the application of radio-frequency substrate bias of different powers from 0 to 15 W. The crystal structures, microstructure, and mechanical, electrical, and optical properties under the effect of bias were characterized. Both the TiVCr and TiVCrZrY films constructed simple solid solutions from all alloyed elements. The TiVCr films possessed a body-centered cubic crystal structure with a pyramid-like surface, while the TiVCrZrY films had a hexagonal close-packed crystal structure with a domelike surface. The microstructure and properties of the films varied with bias power. As the bias power increased, the microstructure of the films obviously changed from a porous to a dense columnar feature, and the density of the voids existing between the columns decreased. Accordingly, the physical properties of the films were improved. The hardness of the TiVCr and TiVCrZrY films was enhanced to about 11 and 14 GPa, and the electrical resistivity was lowered to 80 and 100 μΩ cm, respectively. [ABSTRACT FROM AUTHOR]

In this study, aluminum-doped zinc oxide (AZO) transparent conducting films were deposited as seed layers by sol-gel method, followed by UV exposure and subsequent thermal curing at a low temperature of 300°C. Zinc oxide nanorod arrays were then hydrothermally grown on the seed layers at 70°C. By the activation Of UV exposure, the 300°C cured AZO seed layers possessed an obvious crystallinity and a [002] texture. The well-aligned and vertical growth of high density zinc oxide nanorods with a [002] preferred orientation and strong photoluminescence was consequently accomplished on the UV-exposed seed layers. The zinc oxide nanorods were characterized as single crystals of typical wurtzite structure with a (002) lattice spacing of 0.26 nm. Highly [002] textured grains with small-angle misfits of lattice orientations in the UV-exposed seed layers dominated the aligned growth of the nanorod arrays. [ABSTRACT FROM AUTHOR]

Electromigration reliability tests of dual-damascene Cu interconnect structures with or without a NH3/He plasma treatment have been performed in this study at 400°C under a high current density of 8 MA/cm² to clarify the effect of plasma treatment on the interface structure between Cu wires and SiCN capping layers and on the early-stage electromigration behavior and electrical reliability of the interconnects. From cumulative failure probabilities, small shape factors and large median time to failure were obtained for the interconnects with the plasma treatment, indicating an improved electromigration resistance. The oxide layer on the Cu surface was removed by plasma treatment, and an alternative CuSiN interlayer was formed at the Cu/SiCN interface, enhancing interface adhesion and reducing the diffusion paths of Cu atoms. Therefore, voids nucleated inside the Cu wires, rather than at the interface, at the early stage of the electromigration tests. The change in the Cu/SiCN interface structure varied the early-stage electromigration-induced voiding behavior and then effectively improved the electrical reliability of the Cu interconnect structures. [ABSTRACT FROM AUTHOR]

To inhibit rapid Cu diffusion in interconnect structures, an effective diffusion barrier of high thermal stability is strongly demanded. Thus in this study a nitride nanocomposite film of equimolar five-element high-entropy alloy (AICrTaTiZr)N was developed and deposited by reactive sputtering. Thermal stability of the (AICrTaTiZr)N film and its barrier performance to the interdiffusion of Si and Cu were investigated under thermal annealing at 700-900°C. The (AICrTaTiZr)N film, constructed of mixed crystalline and amorphous nanocomposite structure, was found to remain thermally stable at an extremely high temperature of 900°C with low electrical resistance. Neither interdiffusion between Si and Cu through the (AICrTaTiZr)N layer nor formation of any silicides occurred. Severe lattice distortions caused by the addition of multiprincipal elements and the nanocomposite structure of nanocrystallites surrounded by an amorphous matrix without the existence of grain boundaries were expected as the dominant factors for the high thermal stability and superior diffusion resistance of the (AICrTaTiZr)N film as an effective barrier material. [ABSTRACT FROM AUTHOR]

Amorphous CoWP films have been studied as a capping or diffusion barrier layer to reduce Cu electromigration. However, the interface characterizations between the CoWP and Cu films have not been clarified. Thus, in this study, CoWP and Cu films are deposited by electroless plating, and their thermal stability and interface diffusion behaviors are investigated. By the activation of nanoscaled Pd catalysts, a continuous amorphous CoWP layer is obtained with stable concentrations of 82.5 atom % Co, 5.5 atom % W, and 12.0 atom % P, and then a smooth crystalline Cu film is directly deposited on the CoWP layer. Under thermal annealing at 500°C, the CoWP layer remains an amorphous structure, and no obvious interdiffusion between the Cu and CoWP films is found. The electrical resistivity of the CoWP layer and CoWP/Cu bilayer decreases to the lowest values of 35 and 3.3 μΩ cm, respectively. However with increasing annealing temperature to 600°C, crystallization of the amorphous CoWP occurs, and much severe interdiffusion between the Cu and CoWP films is observed. [ABSTRACT FROM AUTHOR]

In this study, the interface chemistry and adhesion strength between a porous SIOCH extra-low-dielectric-constant film and SiCN etch stop layers were investigated with different plasma treatments. An interlayer of -6 nm thick between the porous SiOCH film and SiCN layers was found to be composed of Si, N, C, and 0. The SiOCH/SiCN interface was constructed by mixing bonds, including Si-C-N, Si-N-C, Si-O-C, Si-O2, etc. Under H2 and NH3 plasma treatments, a large amount of weak Si-CH3 and SiO-CH3 bonds were broken, and more Si-O related bonds of high binding energy formed at the interfaces. Moreover, under the accumulation of sufficient shear stresses around the indented regions during nanoindentation tests, interface delamination between the porous SiOCH film and SiCN layers occurred. The interface adhesion energy between untreated porous SiOCH film and SiCN layers was accordingly measured as 1.68 J/m2. After plasma treatments, especially NH3 plasma, the adhesion strength was effectively improved to 2.13 J/m2. [ABSTRACT FROM AUTHOR]

In this study, the interface chemistry and adhesion strengths between Cu and SiCN etch stop layers have been investigated under different plasma treatments. From the examination of interface microstructures and the analyses of chemical compositions and bonding configurations, an oxide layer was found to exist at the untreated Cu/SiCN interface. After H2 and NH3 treatments, the amount of oxides was effectively reduced. Some Cu silicides formed during SiCN deposition, and Cu nitrides even formed under NH3 plasma treatment. The adhesion strengths of the Cu/SiCN interfaces were measured by nanoindentation and nanoscratch tests under which interface delamination occurred around indented regions. The adhesion energy of the untreated Cu/SiCN interface was obtained as about 4.98 and 0.98 J/m2, respectively, by nanoindentation and nanoscratch tests. After H2 and NH3 plasma treatments, the adhesion energy was effectively improved to 5.90 and 5.99 J/m2 by nanoindentation test, and to 1.74 and 2.58 J/m2 by nanoscratch test, respectively, because of the removing of oxides and the formation of Cu silicides and nitrides at the Cu/SiCN interfaces. [ABSTRACT FROM AUTHOR]