Establishing a cost-effective technology for the metallization of through-Si vias (TSV) is an important factor in the realization and volume manufacturing of 3D-stacked integrated circuits (3D-SIC). Cu electroplating, which is the preferred technique, should provide not only a void-free TSV fill, but also short filling time and small overburden. The duration of the plating process is a significant contributor to the overall 3D process cost, and thus needs to be minimized.The overburden, the thickness of the material deposited on the top surface of the wafer, has to be limited for compatibility with the following processing steps (e.g. chemical mechanical polishing, CMP).In this paper we report on Cu plating of TSV-s with a thin Ta film on the field. The thin Ta film is sputtered on top of the Ta barrier/Cu seed, and inhibits Cu plating outside the TSV-s. We show that the use of this Ta-cap and in situ electrochemical monitoring techniques leads to significant savings in plating and polishing time, and thus savings in manufacturing costs of 3D-stacked integrated circuits.

Important material properties of dielectric oxide films fabricated by aqueous chemical solution deposition, such as crystallization, topography, contamination and interfacial layer were evaluated and related to the films' dielectric properties.

Functional ultrathin films (<20 nm thickness) of zirconia, barium zirconate and strontium niobate were deposited. The films were all subjected to the same thermal treatment, based on the high similarity of their precursors' thermal decomposition behavior. The evolution of the films' chemical purity as a function of temperature and the effect of annealing on the interfacial SiO2 layer was studied by grazing angle ATR-FTIR. The films' crystallization behavior was dependent on film thickness and composition as shown by high temperature XRD. C-V characterization of the films demonstrated a k-value in the same order of magnitude as for the ZrO2 reference material. This is lower than the bulk material's value, thus leaving room for further optimization of the current materials or alternatively selection of other material compositions.

The control and understanding of the incorporation of nitrogen during SiC PVT continues to play an important role in SiC crystal growth. Nitrogen acts both as a dopant and an impurity depending on the growth conditions and desired resistivity. Epitaxial growth by CVD provides some insight into N incorporation in terms of the face effects, temperature, and impact of the chemical species in terms of the C/Si ratio. This paper will present experimental results showing trends regarding nitrogen incorporation during SiC PVT. Various crystal growth processes operated under constant nitrogen partial pressures were found to produce wide ranges of SiC resistivity. These effects will be analyzed in light of the process impact on gas phase elemental composition (1), crystal stress (2), dopant activation (3) and crystal defectivity (4). The goal of this paper is to provide additional insights regarding nitrogen incorporation during SiC PVT, and in turn drive towards a more holistic approach to control the resistivity of 4H n+ SiC material, based on the understanding established from SiC epitaxy technology.

SiC single crystal wafers grown by sublimation exhibit relatively high dislocation densities. While it is generally known that the overall dislocation density tends to decrease throughout crystal growth, there has been a limited quantitative analysis of such trend. In this study, we measured the density of threading dislocations in the wafers sliced from several SiC boules. Although the dislocation density in the wafers sliced from different boules could differ by orders of magnitude, a consistent empirical relationship was found between the dislocation density (ρ) and the axial wafer position within the crystal (w): ρ is proportional to w (−0.5).

Monte Carlo simulations were performed based on two assumptions: (i) during growth the threading dislocations move randomly in the lateral directions, and (ii) two dislocations of opposite sign annihilate when they come within a critical distance between them. Good agreement was achieved between the model and experimental results. The critical distance determined from the simulations was in the range between a few hundred Ă and a micron.

Metal layers can be used as bonding layers at wafer-level in MEMS manufacturing processes for device assembly as well as just for electrical integration of different levels. One has to distinguish between two main types of processes: metal diffusion bonding and bonding with formation of an interface eutectic alloy layer or an intermetallic compound. The different process principles determine also the applications area for each. From electrical interconnections to wafer-level packaging (with emphasis on vacuum packaging) metal wafer bonding is a very important technology in MEMS manufacturing processes.

Membrane techniques for water treatment have been growing significantly for the last decade. Reverse osmosis, for example, is the leading seawater desalination technique. Nanofiltration membranes are used more and more for hardness removal and even to desalinate slightly polluted waters. Ultrafiltration and microfiltration membranes are used extensively mainly as membrane bioreactors in wastewater recovery. While this trend is growing, the membranes still may be improved significantly, based on new materials designed to increase the flux of water through the membranes at reduced pressures while maintaining or even improving the rejection of dissolved matter or suspended matter. Better membranes will reduce energy consumption while maintaining affordable separation properties.

Fabricating horizontally aligned single wall carbon nanotubes (CNTs) with controlled properties has been one of the significant challenges for field-effect transistor (FET) applications. This report demonstrates a novel procedure for the fabrication of horizontally aligned single walled CNTs using the focused ion beam (FIB) and chemical vapor deposition (CVD). This method allows the morphologies, internal structures, and elemental compositions of CNTs to be directly analyzed in the scanning electron microscope (SEM) and transmission electron microscope (TEM) and avoids any sample preparation procedures that might alter the structure of the CNTs. The techniques of electron beam and ion beam induced deposition (EBID and IBID) of Pt electrodes to the CNT ends were compared and both were found to produce metal contamination around the target area. The fabrication of large area electrodes to assist in testing the CNT's electronic properties, including contact resistance and I-V characteristics was investigated. Using this fabrication technique we were able to perform an I-V sweep on a CNT circuit as well as detect the metal contamination on the CNTs which occurred as a result of electrode deposition.

We propose that a thermo-electrical control system for rapid and reversible actuation of biomolecular motors and their partner filaments can also be used to study molecular mechanisms of cardiovascular diseases. We have previously used this device to evaluate the temperature-dependence of unregulated (absence of cardiac Ca2+-regulatory proteins tropomyosin, α-Tm, and troponin, Tn) actin filament sliding powered by myosin motors, which hydrolyze ATP. These assays using the thermo-electric controller can also be applied to regulated thin filaments (F actin plus α-Tm and Tn) to obtain energetic parameters and functional correlates of structural stability at the level of single filaments. This allows us not only to examine Ca2+-dependent sliding of thin filaments, but also to test for altered function of clinically relevant mutations of cardiac myofilament proteins such as those identified in familial hypertrophic cardiomyopathy (FHC).

The texture and microstructure of electrodeposited Ni layers formed in an additive-free Watt's bath were investigated. The microstructure of the electrodeposited Ni layer consists of fine columnar grains extending along the growth direction. The major texture components of electrodeposited Ni layers on Ni-P substrate were (112) and (110) fibers. On the other hand, electrodeposited Ni layers on Cu substrate had a strong (110) fiber texture. In the vicinity of the interface between the electrodeposited Ni layer and the Cu substrate, obvious epitaxial regions were not observed. Many twins parallel to the growth direction were observed in the electrodeposited Ni layer. It is suggested that grains with a twin relationship grew preferentially during the electrodeposition reaction.

An insect heart (dorsal vessel) is well suited as an environmentally robust bioactuator since insect tissue is generally robust over culture conditions compared with mammalian tissue. In this paper, the applicability of a caterpillar dorsal vessel to a bioactuator was assessed by fabricating a micropillar actuator driven by dorsal vessel tissue and evaluating the response to electrical pulse stimuli. The actuator worked autonomously for more than 90 days at 25 °C without any maintenance. The average frequency and displacement for 30 s on the 28th day of culturing were 0.83 Hz and 41 μm, respectively. Furthermore, as a regulation method for the dorsal vessel, electrical pulse stimuli were applied to the micropillar actuator. The contractile delay was about 50 ms. A twitch contraction was evoked by electrical pulse stimulus at 20 ms in duration and 10 volts in amplitude. A tetanic contraction was observed when stimuli over 10 Hz were applied.

It is now apparent that future generations of fast electronics and compact sensors may need to rely increasingly on integrated optical components. But integration of electronics and photonics in today's IC's is challenging. Silicon, the ubiquitous electronic material, is neither ideally suited for most photonic functions nor readily integrated with most of the common photonic materials, such as GaAs. The approach we describe here relies on GaN-based films, which can be grown directly on silicon substrates and hence can be potentially integrated with state-of-the-art Si-based electronics. We have demonstrated the fabrication of GaN structures on silicon wafers ranging in overall size from sub-micron to several millimeters, all containing highly accurate individual features on the nm scale. As proof of concept, we have fabricated GaN optical waveguides and photonic crystals containing optical cavities by patterning GaN membranes grown directly on Si wafers. Our optical cavities were designed to have resonant modes within the spectral region of the broad defect-induced luminescence of GaN. We have measured sharp resonant features associated with these cavities by optically pumping above the GaN band edge, and have compared the data to numerical simulations of the spectra. Our results to date demonstrate the feasibility of fabricating high-quality GaN photonic structures directly on Si wafers, thereby providing a possible path to achieving true integration of electronics and photonics in future generations of IC's.

Organic light emitting diodes (OLED) are efficient light sources based onorganic semiconductors. Unlike inorganic LEDs which are more or less pointsources, OLED are planar light sources with up to 1 m2 in area.By using organic materials, they are cheap to produce and economical to use.The determination of triplet exciton energy levels is of interest for thedevelopment of efficient OLED, based on the fact that electrical excitationusually creates three times as many triplets as singlets. Additionally, theknowledge of these energy levels is crucial for the design and choice ofemitter matrix materials and exciton blocking layers. These values arenormally determined by photoluminescence (PL) measurements in solution formaterials which show intersystem crossing (ISC) between singlet and tripletstates. For some materials, the triplet levels cannot be measured this waybecause some materials prohibit ISC. In this work, a method is presentedwhich allows the determination of the energy levels using low-temperatureelectroluminescence (EL) spectroscopy. The dependence on ISC is avoided bycreating triplets directly with electrical excitation and this allows tomeasure a large class of organic materials. A low-temperature EL spectrum ispresented forN,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (TPD) ina 3-phenyl-4-(1‘-naphthyl)-5-phenyl-1,2,4-triazole (TAZ) matrix (TPD/TAZ1:3) at 77 K. Triplet emission is only observed at very low charge carrierdensity (0.5 μA/mm2). Quenching processes are analyzed usingcombined EL and PL measurements and unipolar devices. Two factors can be thecause of the quenching: A strong quenching based on a low concentration ofelectrically activated impurities could explain the dependency. The otherexplanation points to a quenching based on electrons in the emitting layer.This might be explained with triplet-polaron quenching (TPQ). TPQ isproportional to the charge carrier density and contributes the dominant partto the quenching at low current densities.

In this work, hybrid atomistic-macroscale simulation is conducted to explore the crystallization process of Si surface in the situation of fast melting and solidification induced by ultrafast laser heating and heat conduction. Using the environment-dependent interatomic potential, samples containing 2,880 and 11,520 Si atoms are modeled to provide accurate details for the relationship between the finial crystal structure and the parameters of laser pulses. For different pulsed lasers, amorphous layers are found to form when the laser fluence exceeds a certain critical value. An empirical correlation Ec = 448.76 × (tg )0.56 is obtained to relate this critical fluence to the laser pulse width. It is found that the final thickness of amorphous layer is related to the fluence of the laser pulse with the same full width at half maximum (FWHM). Employing laser pulses with FWHM = 6.67 ns, the formation and recrystallization processes of a 12 nm thick amorphous layer is further investigated, which may have great potential in laser manufacture techniques for Si-associated structures.

Isothermal crystallization of doped SbxTe fast-growth phase-change films was investigated using transmission electron microscopy with in situ heating. SbxTe films with four different values for the Sb/Te ratio, x=3.0, 3.3, 3.6 and 4.2, were analyzed and the films were sandwiched between two types of dielectric layers. One dielectric layer type is based on 80at.%ZnS-20at.%SiO2, the other on (Ge,Cr)N. The crystal growth rates reduce if the phase-change films are sandwiched between amorphous dielectric layers. The reduction is very pronounced at the lowest measured temperatures (150 °C), becomes smaller at higher temperatures and probably disappears at around 200 °C. The crystal growth rates increase with increasing Sb/Te ratio, but the activation energy for crystal growth is not significantly affected by the Sb/Te ratio. Finally a systematic study of the effect of the electron beam of the TEM on the crystal growth rates is performed showing accelerated growth rates. The present work shows that particularly at relative low temperatures, just above the glass-transition temperature, the growth rates as limited by the atomic mobilities are sensitive to various (boundary) conditions, e.g. capping layers and irradiation.

TiO2 nanotube arrays had been selected as electron transport material incorporate with P3HT:PCBM blended polymer to fabricate the hybrid organic-inorganic solar cells. Well aligned TiO2 nanotube arrays has been synthesized though the liquid phase deposition by using ZnO nanorod arrays as templates. Three types of dyes (viz. NKX-2677, D149, N719) were adsorbed onto the surface of TiO2 nanotube arrays to increase the interfacial contacts between the organic polymer and inorganic metal oxide. Surface modification with NKX-2677 exhibited remarkable improvement of the cell efficiencies in terms of current density, open circuit voltage, and fill factor as compared with those of other dyes.

Conductive zinc oxide (ZnO) films are used extensively as transparent electrodes in thin-film photovoltaic solar cells. Compared with the widely used indium tin oxide (ITO) and tin oxide (SnO2), ZnO has a smaller optical bandgap. ZnO is commonly used as a front contact for copper indium gallium diselenide (CIGS) solar cells, but it forms a small, unfavorable conduction-band offset with the CdS layer. The optical bandgap of ZnO could easily be engineering by alloying with MgO or CdO. In this work, we try to optimize the ZnO for CIGS solar cells. The optical and electrical properties of Zn1-xMgxO:Al films fabricated by co-sputtering were studied. Two targets: ZnO:Al and MgO, were used. The ratio of ZnO/MgO was varied continuously on the 6”x6” glass substrate, and the effects of composition on the properties of the Zn1-xMgxO:Al films were investigated. The carrier concentration and mobility of the Zn1-xMgxO:Al films decreased quickly with increasing Mg content. However, the optical properties of the Zn1-xMgxO:Al films do not vary linearly with Mg content, as reported by most papers. The observed optical bandgap of Zn1-xMgxO:Al films is actually first narrowed, then increased with the Mg content. The shift in optical bandgap from narrow to wide occurs at around a composition of x = 0.07. After the point of x = 0.07, the bandgap width star increase but film sheet resistance already too low. Our result therefore suggests that the alloyed Zn1-xMgxO:Al does not benefit the CIGS solar cell.

Low temperature (150 °C) deposition of doped and undoped polycrystalline Si (poly-Si) as well as SiNX films on polyethylene terephthalate (PET) films has been achieved with practical deposition rates by using pulsed-plasma CVD under near-atmospheric pressure. The precursor is SiH4 diluted in H2 for poly-Si while N2 has been additionally used for SiNx. No inert gases such as He was used. A short-pulse based power system has been employed to maintain a stable discharge in the near-atmospheric pressures. With this technique, deposition of poly-Si thin film with virtually no incubation layer is possible, which in the case of P-doped poly-Si shows a Hall mobility (μH) of 1.5 cm2/V·s.

New technique to separate bulk and interface electrical properties of polycrystalline and glassy Ge2Sb2Te5 (GST) in phase-change memory (PCM) devices is proposed. PCM with different GST thicknesses are measured. The average activation energies for bulk conductivity are 0.37 eV and 0.09 eV as well as bulk resistivities are about μOhm*cm2 and 20 μOhm*cm. The contact barriers is 0.07eV and specific contact resistance is about 0.3 μOhm*cm2 in studied PCM devices.

It is discovered that bulk resistivities for both SET and RESET states in PCM obey Meyer-Neldel rule with almost identical isokinetic temperatures 335K − 340K. This information is discussed in terms of GST structure.

Exploratory synthesis of mixed oxides of rhodium has produced many new rhodates containing both Rh3+ and Rh4+. The structures of all the compounds are based on networks formed from RhO6 octahedra sharing both corners and edges.All compounds exhibit good electrical conductivity, and some also show a high thermopower.

We report on nano-scale optical effects of amorphous silicon layer conformally deposited on randomly textured zinc oxide layers on glass substrates investigated by near-field scanning microscopy. Such textured layers are used in thin-film photovoltaic devices to enhance light trapping. Experimental results are compared to theoretical data, obtained from large scale finite-difference time-domain simulations. Light localization on the surface of the textured interface and a focusing of light by the structure further away are observed. The measurements are compared with simulations, which provide additional insight into the light intensity distribution inside the solar cell on a nm-scale. It will be shown how this information can be used to optimize light trapping in thin-film solar cells using an amorphous silicon solar cell as an example.