Toranosuke Ashizawa

Effect of Pad Surface Micro-Texture on Coefficient of Friction and Removal Rate during Copper CMP Process

In this study, 200-mm blanket copper wafers were polished on an IC1010 M-groove pad, which was conditioned by a 3M A2810 disc and Mitsubishi Materials Corporation (MMC) TRD disc. Pad surface contact area and topography were analyzed using laser confocal microscopy and scanning electron microscopy. The MMC TRD disc generated a lot of large near contact areas corresponding to fractured and collapsed pore walls. The fractured and collapsed pore walls partly covered the adjacent pores, making the pad surface more lubricated during wafer polishing and rendering significantly lower coefficient of friction and removal rate than the 3M A2810 disc.

A New Cerium-Based Ternary Oxide Slurry, CeTi2O6, for Chemical-Mechanical Polishing

A new ternary oxide slurry, CeTi2O6 containing Ce4+ ions, was found to be effective as an abrasive in chemical-mechanical polishing (CMP). The ternary oxide was synthesized by the Pechini polymerizable complex (PC) method. X-ray diffraction (XRD) Rietveld analysis indicated that the oxide possesses a single CeTi2O6 phase of a brannerite structure (C2/m, No. 12). When CeTi2O6 was used as an abrasive slurry for polishing thin oxide film, the removal rate was as high as that of ceria (CeO2) slurry.

Effect of Pad Surface Roughness on SiO2 Removal Rate in Chemical Mechanical Polishing with Ceria Slurry

The effect of pad surface roughness on SiO2 removal rate was investigated using four different slurries containing ceria (CeO2) powders of different crystallite sizes and mean particle sizes. A clear maximum was observed in the dependence of removal rate on pad surface roughness. The four ceria slurries showed a peak in blanket wafer removal rate against pad surface roughness Ra. The peak moved toward larger Ra values with decreasing ceria crystallite size. The removal rate was strongly influenced not only by pad surface roughness but also by the crystallite size of ceria in the slurry.

Effect of Pad Surface Micro-Texture on Removal Rate during Interlayer Dielectric Chemical Mechanical Planarization Process

The effect of pad surface micro-texture on removal rate in interlayer dielectric chemical mechanical planarization was investigated. Blanket 200-mm oxide wafers were polished on a Dow® IC1000TM K-groove pad conditioned at two different conditioning forces. The coefficient of friction increased slightly (by 7%) while removal rate increased dramatically (by 65%) when conditioning force was increased from 26.7 to 44.5 N. Pad surface micro-texture analysis results showed that pad surface contact area decreased dramatically (by 71%) at the conditioning force of 44.5 N, leading to a sharp increase in the local contact pressure and resulting in a significantly higher removal rate.

Effect of cerium oxide particle sizes in oxide chemical mechanical planarization

This study explored the effect of different cerium oxide abrasive particle sizes in chemical mechanical planarization of 200 mm blanket plasma-enhanced tetraethylorthosilicate wafers. All polishing experiments were done with a polisher and tribometer capable of measuring shear force and down force in real-time. Coefficient of friction and removal rate were found to correlate well with the slurry median particle size distribution. Removal rate modeling based on particle size was explored to support the interpretation of the experimental results.

Variation of Composition in a Bi(Pb)-Sr-Ca-Cu-O Grain and the Influence of Mg and Ba Doping on Its Superconductivity

The 110 K phase (2223) and (Sr, Ca)-Cu-O phase exist in the Bi(Pb)-Sr-Ca-Cu-O ceramics. The Cu content varies in the perpendicular direction of platelike 2223 grains, but little variation is observed on the planer surface of the grains along their length. Only the 110 K phase was found in the X-ray diffraction pattern of Bi(Pb)-Sr(Ba, Mg)-Ca-Cu-O. Its electrical resistivity became zero at 110 K. By the partial substitution of Mg and Ba for Sr, the range of sintering temperatures in which we obtained a higher Tczero was much larger than that for Bi(Pb)-Sr-Ca-Cu-O.

Effect of Pad Micro-Texture on Frictional Force, Removal Rate, and Wafer Topography during Copper CMP Process

In this study, the effect of pad micro-texture on frictional force, removal rate, and wafer topography during ILD/STI CMP processes was investigated. Blanket 200-mm TEOS wafers and SKW3-2 patterned STI wafers were polished on an Araca APD-500 polisher and frictional force was measured in real-time during polishing. Two diamond discs (3M A2810 diamond disc and Mitsubishi Materials Corporation (MMC) diamond disc with triple ring dot (TRD) design) were used to condition an IC1000 K-groove pad with Suba IV sub-pad during wafer polishing. For each diamond disc, two conditioning forces (6 and 10 lb) were used. Under each conditioning force, five blanket TEOS wafers and three SKW3-2 STI wafers were polished at 4 PSI and 1.2 m/s. Pad samples were taken after blanket TEOS wafer polishing, as well as after patterned STI wafer polishing. Pad contact area and surface topography were analyzed using laser confocal microscopy. Pad contact area, pad surface abruptness, and pad summit curvature were obtained. When the conditioning force increased from 6 to 10 lb, the COF and removal rate increased for both diamond discs while the pad contact area decreased from 0.053% to 0.036% and from 0.040% to 0.011% for the 3M A2810 disc and MMC TRD disc, respectively. The contact area during patterned wafer polishing was larger than that during blanket wafer polishing for both diamond discs at 6 and 10 lb conditioning forces. In addition, the pad surface was less abrupt and the mean summit curvature was smaller during patterned wafer polishing than that during blanket wafer polishing for both diamond discs at 6 and 10 lb conditioning forces. Dishing and erosion analyses were performed on 100-micron pitches on the wafer center with different pattern densities. The MMC TRD disc generated higher dishing and erosion than the 3M A2810 disc under both 6 and 10 lb conditioning forces. The mean summit curvature of the MMC TRD disc was larger than that of the 3M A2810 disc at both 6 and 10 lb conditioning forces during patterned wafer polishing, indicating sharper pad summits contributed to higher dishing and erosion for the MMC TRD disc.

Chemical Mechanical Polishing with Nanocolloidal Ceria Slurry for Low-Damage Planarization of Dielectric Films

New chemical mechanical polishing processes using nanocolloidal ceria slurry are proposed for high-precision and low-damage planarization of silicon-dioxide-based dielectric films. In the polishing process of a shallow trench isolation structure, a hard pad and a cationic polymer additive are used in combination with the slurry. The new process is effective in improving the planarity and reducing the microscratch count in comparison with a conventional polishing process with calcined ceria slurry and a standard pad. In the polishing process of an interconnect structure with ultralow-k interlayer dielectrics (ULK-ILDs), the standard pad should be used since the ULK-ILDs are easily damaged. By employing a spin-on-type ULK-ILD having a self-planarizing effect, a high planarity is obtained when using the nanocolloidal ceria slurry with the standard pad. The electrical measurement of the interconnect structure indicates that dielectric damage due to the process is successfully suppressed.

Formation of 2223 Phase and Variation in Composition of Bi(Pb)-Sr-Ca-Cu-O Superconductors

Sintering of Bi1.6Pb0.4Sr2Ca2Cu3.6Ox for long time resulted in an increase of the volume fraction of the 2223 phase to 53%. The 2223 phase appears to take the form of flaky grains. The chemical composition of the constituents of the flaky grains are not exact stoichiometric proportions. Substances in the calcined powder start to react around 832°C, then change to (Sr,Ca)-Cu-O and an unknown phase at 862°C. Growth of the 2223 phase is enhanced between these two temperatures.

Superconducting Properties of Y-Ba-Cu-O Sheet by a Tape Casting Method

YBa2CuO3O7-δ (YBCO) superconducting sheets were successfully fabricated by a tape casting method. Critical temperature (Tczero) was 92.IK with a tape sintered at 940°C for 10 hours in oxygen. The (001) planes of YBCO particles were oriented parallel to the casting plane of the 9 green sheet. The highest Jc was 1,510A/cm2 at 77K in zero magnetic field. It is supposed that the grain orientation contributed principally to the enhancement of Jc of the YBCO sheet.