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Low κ Organosilicate Glass (OSG) films are being proliferated into new IC device architectures with CMP requirements spanning a wide range (highly selective to non-selective, low polish rates to high polish rates). This study aims to understand the relationship between these OSG film properties (both bulk and surface) and their planarization response, especially removal rate (RR). Eight OSG films were polished along with TEOS oxide using two barrier slurries. The films ranged in carbon content from 8 to 24 % and in nanoindentation elastic modulus from 5.5 to 21.8 GPa. Counterintuitively, higher mechanical strength (i.e., hardness, elastic modulus) of the low κ film did not result in lower polish rates; but was in agreement with previously noted behavior [1]. Removal rates also did not correlate to key OSG film properties such as refractive index (RI), dielectric constant (κ), or total carbon content (by X-ray photoelectron spectroscopy). However, an inverse relationship was observed between RR and the bulk chemical bonding structure (Si-CH3/Si-O ratio) as determined by transmission infrared spectroscopy (FT-IR) measurements (see Figure 1). In addition, a correlation between RR and OSG film’s surface free energy post-polish (measured from water and diiodomethane contact angles) was also observed. Based on the above findings, a mechanistic understanding of low κ OSG polishing was developed. [1] L. Matz, M. Haas, M. O’Neill, R. Sawayda, A. Meyers, in Advanced Metallization Conference (AMC) (eds A. J. McKerrow, Y. Shacham-Diamand, S. Shingubara and Y. Shimogaki), Materials Research Society, Warrandale, PA, 463 (2009) Figure 1

The reversal of the α- to θ-Al2O3 phase transformation and the induced microstructure evolution of boehmite-derived discrete nanosized α-crystallites are examined. Three categories of α-crystallites smaller than 100 nm were examined and found to have similar behavior: (1) pre-existing α-crystallites, (2) α-crystallites formed in situ during the calcination of θ-crystallites of sizes near the critical size, 25 nm, and (3) α-crystallites formed in situ by the thermal treatment of as-received θ-crystallites. The α-crystallite may transform back to the θ-phase above 800 °C. The backwards θ-crystallite may also re-transform to the α-phase again. Because of the density difference between α- and θ-Al2O3, the strain involved in the volume expansion and shrinkage during the phase transition eventually results in the formation of a twinned and/or mosaic structure for the θ- and α-crystallites. A strain release model representing the microstructure evolution of the α- to θ-phase and the θ- to α-Al2O3 phase transformation is proposed.

Direct evidences of cerium valence state transformation from Ce4 + to Ce3 + in an anode-supported solid oxide fuel cell after long-term operation have been identified. Single cell with samarium-doped ceria (Sm0.2Ce0.8O2 − δ, SDC) thin film electrolyte is prepared with maximum power density of 608 mW cm− 2 at 650 °C when the fuel/oxidant flow rates are 335/1005 sccm, respectively. The long-term durability tests are executed by fixed-current operation for 950 h. The power density and voltage degradation are observed and critically attributed to the chemical state transformation of cerium in the electrolyte. From X-ray photoelectron spectroscopy (XPS), the Ce3 + ratio increases from 30.3 to 52.9% in the electrolyte before and after operation. The focused ion beam (FIB)/transmission electron microscopy (TEM) techniques are utilized to investigate the structure variation and the selected area diffraction patterns of the chosen grains towards electrodes identify the phase transformation from CeO2 to Ce2O3, suggesting that the Ce3 + species increase at the near-anode side. The direct evidence of Ce3 + presence shows one of the key factors for the degradation of a low temperature solid oxide fuel cell (LT-SOFC).

The growth characteristics of θ-Al2O3 crystallites in θ-Al2O3 powder systems with sizes 2O3 powders, with mean particle sizes of 12.0 and 20.4 nm, and their mixtures at various weight ratios were homogenized and fabricated into compacts, representing powder systems with various mean sizes and packing densities. The growth characteristics of these powder systems were then examined in the compacts using X-ray diffracion, transmission electron microscopy, differential thermal analysis, and Brunauer–Emmett–Teller adsorption techniques. It was found that the θ-Al2O3 crystallites in the powder system were coarsened by the coalescence of θ-crystallites of similar sizes. Powder systems, even with different mean sizes, exhibited similar growth rates that could be expressed by the reduction of their surface area per unit volume per time. The smaller crystallites initiated growth by coalescence at lower temperatures, while the larger crystallites maintained their sizes until the smaller ones reached their size; then, both grew simultaneously. Thus, it is possible for a powder system ultimately to develop θ–crystallites of similar size that lead to a simultaneous θ-to-α-Al2O3 phase transformation during thermal treatment. The increase in the packing density of the powder systems caused θ-crystallite growth to begin at lower temperatures.

Dense electrolyte films ∼15 μm thick made of samarium-doped ceria (SDC) are fabricated by spin-coating. The SDC powders are synthesized by the glycine nitrate combustion process. It is found that nanoscale SDC powders can be obtained at 1000 °C. Cells constructed with an SDC electrolyte, a NiO + SDC composite anode, and an SSC–SDC/SSC bi-layer cathode are fabricated and tested at temperatures from 400 to 650 °C. SEM micrographs show that the SDC electrolyte layer adheres well to the porous anode and the cathode. The maximum power densities of the cell are 38, 84, 185, 303, 438, and 549 mW cm −2 at 400, 450, 500, 550, 600, and 650 °C, respectively. Analysis of the impedance spectra indicates that the electrode polarization dominates the total cell resistance at temperatures below 550 °C, and the ohmic resistance dominates the total cell resistance above 550 °C. The activation energies of the resistances show that the cell performance is significantly controlled by the electrode polarization resistance. Durability tests are performed over 950 h and indicate that the power density and the voltage gradually degrade with time at a rate of ∼0.03 mW cm −2 h −1 and ∼0.07 mV h −1 , respectively. Hence, a low-temperature solid oxide fuel cell has been developed.

Crystal-growth-related microstructures and the length-to-diameter ratio of a single-crystal-type α-Al 2 O 3 nanofiber were examined using HR-TEM techniques. The fibers exhibited diameters ranging from 50 to 100 nm and lengths of several tens of micrometers. During thermal treatments, the alumina fiber went through phase transformations similar to boehmite. Therefore, the phase evolution, especially the final θ- to α-Al 2 O 3 stage of the phase transformation, may be the determining factor in the microstructural evolution of the nanofibers. HR-TEM techniques were utilized to demonstrate that the single crystals were formed by the coalescence of well-elongated α-Al 2 O 3 colonies. The fibers grew in the [1 1 0] or [1 1 2] direction instead of [0 0 1]. A thermodynamic analysis revealed that if the α-Al 2 O 3 nanofiber that transformed from θ-Al 2 O 3 behaved in a stable manner, there could be a size ratio limit for the length and diameter of each α-Al 2 O 3 colony. The smallest potential diameter was calculated to be around 17 nm.

The Sm 0.5 Sr 0.5 CoO 3− δ (SSC) with perovskite structure is synthesized by the glycine nitrate process (GNP). The phase evolution of SSC powder with different calcination temperatures is investigated by X-ray diffraction and thermogravimetric analyses. The XRD results show that the single perovskite phase of the SSC is completely formed above 1100 °C. The anode-supported single cell is constructed with a porous Ni–yttria-stabilized zirconia (YSZ) anode substrate, an airtight YSZ electrolyte, a Sm 0.2 Ce 0.8 O 2− δ (SDC) barrier layer, and a screen-printed SSC–SDC composite cathode. The SEM results show that the dense YSZ electrolyte layer exhibits the good interfacial contact with both the Ni–YSZ and the SDC barrier layer. The porous SSC–SDC cathode shows an excellent adhesion with the SDC barrier layer. For the performance test, the maximum power densities are 464, 351 and 243 mW cm −2 at 800, 750 and 700 °C, respectively. According to the results of the electrochemical impedance spectroscopy (EIS), the charge-transfer resistances of the electrodes are 0.49 and 1.24 Ω cm 2 , and the non charge-transfer resistances are 0.48 and 0.51 Ω cm 2 at 800 and 700 °C, respectively. The cathode material of SSC is compatible with the YSZ electrolyte via a delicate scheme employed in the fabrication process of unit cell.

The possibility of eliminating finger or vermicular growth of α-Al2O3 particles obtained by calcination of boehmite was examined. Heterogeneous precipitation of boehmite in a well-dispersed θ-Al2O3 suspension was first prepared, in which the mass ratio of boehmite to θ-crystallite was evaluated to form agglomerates of similar sizes that will form α-Al2O3 crystallites of

The inter-particle relationship effects on a temperature reduction and simultaneity of α -crystallite formation during θ - to α -phase transformation were examined using DTA, XRD, and TEM techniques. Three powder systems derived from the same θ -powder of average crystallite size 15.2 nm were prepared, with the intention of creating different microstructure for each powder systems as: (1) as-received, (2) pre-treated by homogenization with a mechanical stirring accompanied by pH adjustment for dispersion, and (3) homogenized and additionally uniaxial-pressed to compacts with higher bulk density. Activation energies of θ -crystallite growth occurring in the three powder systems were also obtained based on an isothermal model of grain growth rate equation. It is found that the temperature reduction characteristics can be related to the homogeneity as well as the inter θ -Al 2 O 3 crystallite distances behaved by the θ -crystallites. Higher homogeneity and shorter inter-crystallite distance for the θ -powder systems may favor the α -crystallite formation at lower temperatures over a shorter duration of phase transformation. Furthermore, activation energies of θ -crystallite growth can be reduced. And α -Al 2 O 3 powders fabricated can be mono-sized and free of vermicular growth.

This study examines inducing an additional phase transformation subsystem using α-Al2O3 seeding techniques in a θ-Al2O3 powder system that undergoes θ- to α-phase transformation. It is found that seeding induced subsystem occurs independently at temperatures lower than that of the parent (original) θ-powder system. The whole system is composed of two parallel and subsequently occurring phase transformation systems during the heat treatment: the seeding-induced subsystem and the residual parent system. The fraction of the seeding induced subsystem in the whole system increases and eventually can become predominant with greater amounts of α-Al2O3 added. The subsystem achieves faster growth of θ-crystallites up to the critical size (dcθ) of phase transformation and can begin the transformation at a lower temperature. Thus as the seeding-induced subsystem becomes predominant, the phase transformation behavior of the parent system is gradually obscured and is finally replaced by that of the subsystem, with an apparent reduction in transformation temperature of the overall system. The seeding affected subsystem exhibited lower activation energy in nucleation stage of the phase transformation. However, the activation energy of the growth stage for both seeded and unseeded systems may have similar values.

Cationic additives are generally used in coated inkjet printing paper to improve water fastness. This study develops a coating for photographic inkjet printing paper that achieves good water fastness without cationic additives. Porous χ- Al 2 O 3 flake powder, which has high porosity, high specific surface area, and positive surface charges, is used as a pigment in the coating. The water fastness of prints is evaluated using an immersion method combined with the measurement of light absorbance of the water used for immersion. The results indicate that water fastness can be improved by introducing χ- Al 2 O 3 powder into the coating pigments. The intrinsic crevices and pores of χ- Al 2 O 3 provide concave sites for dye colorants and enhance the sorbtion of liquid phase of inks, but stick the dye colorants on the pigment surface. Furthermore, the positive surface charge of χ- Al 2 O 3 provides cationic sites for the fixation of dye on the coating surface via electrostatic interactions.

The anode-supported solid oxide fuel cells (SOFCs) with an yttria-stabilized zirconia (YSZ) electrolyte have been successfully prepared by the sequential steps of fabricating technique including tape casting, spin coating, and screen-printing. Two types of the SOFCs are manufactured and their cell performances are characterized via the detail analysis of the electrochemical impedance spectroscopy (EIS). The maximum power densities are 411 and 289 mW/cm 2 for the high and low performance cells at 800°C, respectively. According to the EIS analysis, the electrochemical performance of the poor cell is dominated by the anodic non-charge-transfer resistance, which is mainly resulted by the gas diffusion polarization due to the low porosity of the anode. The high performance cell is controlled by the simultaneous contributions of the ohmic resistance (R O ), the anodic polarization (R AP ), and the cathodic polarization (R CP ) at the operation temperature of 800°C. However, the R CP will dominate the performance of the cell as the temperature is lowered down to 700°C.