| The efficient green luminescence of LaPO4:Ce3+,Tb 3+ (monoclinic monazite-type structure) has been known, but only recently has the material gained importance as a fluorescent lamp phosphor. The challenge lies in the coating of LaPO4 onto core material. In the current work, uniform needle-like lanthanum phosphate particles doped with praseodymium have been prepared by hydrolysis of an aqueous mixture of sodium dihydrogen phosphate and lanthanum sulfate in the presence of urea. The LaPO4 particles are of a width of ∼10 nm and a length of ∼80 nm. The attachment of these particles to cores (supplied by GE) is achieved either by the electrostatic attraction of the preformed particles with the cores or by preparing them in the presence of cores. Tests have shown high quantum efficiency of such composite powders.; The role of the length of carbon chain, the presence of single, double and triple bonds in the chain and cis and trans isomers of different dicarboxylic acids on polishing copper in the presence and in the absence of fumed silica particles was investigated. The dissolution and polish results were analyzed in terms of copper-complexing with these additives. Succinic acid and fumaric acid which formed surface films at pH 4 showed high polish rates while exhibiting low dissolution rates. These results indicate that slurries containing these complexing agents can give better planarization of copper. In the pH range of 3-4 (often used for copper CMP), oxalic and malonic acids are found to be most efficient in Cu removal, but also show high dissolution rates. For practical applications the latter can be controlled with inhibitors like ADS and/or BTA.; Zhenyu Lu [11,12] showed that the total surface area of the solids in the slurry controlled the rate of material removal by silica for both Cu and Ta. This work was however incomplete because, all the experiments were conducted with a glycine-peroxide based slurry. Also, only limited study was done by Zhenyu Lu [11] on the effect of pH. With these drawbacks in mind, the current work was done to investigate the effect of surface area of the abrasive particles (colloidal silica particles---Nissan Chemicals Inc.) in the presence of complexing agents other than glycine. Five other complexing agents (maleic acid, succinic acid, citric acid, acetic acid and alpha-alanine) were investigated. Hydrogen peroxide was used as the oxidizer in all the experiments. It was found that the contact area model is also applicable to maleic acid and succinic acid based systems besides glycine, but not for several other complexing agents investigated. And, pH seems to play a major role in the applicability of the model. |
