Presence Of By-products Research Articles

Effect of Polish By-Products on Copper Chemical Mechanical Polishing Behavior

The stains on the pad caused by polishing by-products can be observed in a copper chemical and mechanical polishing (CMP) process. In this study, the effects of stains on CMP performance such as erosion, dishing, and nonuniformity were evaluated as a function of the degree of stains accumulated on the pad. The stains on the pad deteriorate the nonuniformity of removal rate and result in the increase in erosion and dishing. CMP by-products adhere on both pores and grooves of the pad and block the flow of slurry through the grooves, resulting in the deterioration of nonuniformity. The selectivity (ratio of removal rate, Cu to TaN or dielectric film) is important in order to minimize erosion. When wafers were polished on a stained pad, the removal rate of Cu decreased due to the poor slurry distribution and the selectivity decreased more than 40% because the mechanical abrasion was enhanced by the presence of by-products on pad surfaces. The lower the selectivity, the higher the level of erosion on the polished patterned wafers. The higher frictional force on a stained pad results in higher temperature and etch rate of Cu which might be the reason for recess and dishing of Cu lines.

A Kinetic Model of the Hydrogen Peroxide/UV Process for the Treatment of Hazardous Waste Chemicals

The effectiveness of the H2O2/UV process has been investigated using trichloroethylene (TCE), tetrachloroethylene (PCE), benzene, and toluene as model compounds. The UV source used in this study was the low pressure mercury vapor lamp using mainly 254 nm of radiation. For irradiation of aromatic compounds such as benzene and toluene at high concentration, by-products formed by the irradiation process were found to reduce the oxidation rate; these by-products also acted as UV absorbers in competition with the parent compounds. A kinetic model for the rate of direct photolysis of organics has been developed illustrating a method of measuring quantum yields of photolysis in the presence of by-products. It was also found that the addition of peroxide enhanced the oxidation rate. The enhancement rate of TCE was greater than that of benzene even though kbenzene,OH is greater than kTCE,OH. The overall rate of the H2O2/UV system was found to depend on the relative importance of the OH radical pathway, the direct photolysis reaction rate, and the absorptivity of by-products at 254 nm.

Stability of the chain structure of a styrene–isoprene diblock copolymer during the hydrogenation by diimide

AbstractOlefinic double bounds of a model styrene–isoprene diblock copolymer were hydrogenated using diimide (generated by a thermal decomposition of p‐toluenesulfonyl hydrazide). The presence of byproducts and/or main‐chain structural alterations (e.g., degradation or cross‐linking), as a possible side effect of this polymer analogous reaction, was checked by NMR spectroscopy, elemental analysis, static and dynamic light scattering, and GPC. A twofold concentration of Irganox 1010 antioxidant in the reaction mixture (as compared to the original reported procedure) seems to inhibit the formation of byproducts as well as to prevent any alterations on the macromolecular level. No reactions of isoprene monomer units (other than the addition of hydrogen atoms) and no changes in molar‐mass distribution of the substrate were detected by the methods used.

Titanium-catalyzed cyclotrimerization of butadiene Part III. Formation of catalytic bis(di-μ-chloroaluminate)-Ti(II) complexes in TiCl 4Et xAlCl 3- x ( x=1–2) systems

The TiCl 4+ nEt x AlCl 3- x and TiCl 3+ nEt x AlCl 3- x ( x=1–2) systems catalyze the cyclotrimerization of butadiene to ( Z,E,E)-1,5,9-cyclododecatriene (( Z,E,E)-CDT) with a selectivity very similar to that exerted by the analogous (C 6H 6)Ti II(AlCl 4) 2 ( Ia)-based systems. The presence of (benzene)Ti II complexes in the final reaction mixtures of the kinetic runs was observed by electronic absorption spectroscopy in the systems with x=1 for n⩾40, with x=1.5 for n=6–50 and with x=2 for n=6, using the high-intensity CT band at 400 nm. The content of (benzene)Ti II complexes was also estimated from the intensity of the ESR signals of Cp*TiAl 2Cl 8− y Et y ( y=0–4) complexes rapidly formed in all the reaction mixtures after addition of pentamethylcyclopentadiene (Cp*H). It follows from spectroscopic observation of (benzene)Ti II complexes after kinetic runs and comparison of the reaction rates in the TiCl 4− and Ia-based systems that the concentrations of the catalytic (L)Ti II (L = benzene, butadiene, intermediate dimer of butadiene, ( Z,E,E)-CDT or 1,5-COD) complexes are generally lower in the former systems and decrease with increasing x. In the TiCl 4 (TiCl 3) + nEt x AlCl 3- x ( x = 1, 1.5) systems, an excess of the ethylaluminium components results in increased formation of the catalytic (L)Ti II species; however, the reaction rate appropriate to the (L)Ti II concentration is decreased by the retarding effect of EtAlCl 2. The optimum catalysts, exerting the best selectivity for ( Z,E,E)-CDT formation (90.5%), were found in the ethylaluminium sesquichloride systems with new maxima of activity discovered for the ratios Al/TiCl 4 = 6 and Al/TiCl 3 = 4. The TiCl 4 (TiCl 3) + nEt 2AlCl systems have low activity, probably due to the low equilibrium concentration of the (L)Ti II species. The presence of another catalytic species in these systems is manifested by the presence of byproducts ( E,E,E)-CDT and 1,5-COD.

The Chemistry of Pyrrolic Compounds. LVIII. meso-substituted Porphyrins. Further Observations on the Oxidative Cyclization of Bilenes-b

The oxidative cyclization of a series of bilenes -b carrying substituted methyl groups at a terminal site (1d-i) has been investigated as an approach to the synthesis of meso-substituted porphyrins . Although in most cases the required porphyrin was formed the yield was generally low and the sequence complicated by the presence of by-products. The usefulness of this procedure as a route to meso -substituted porphyrins is therefore limited although the identification of the by-products has increased our general understanding of the mechanism of the oxidative cyclization.

Intrinsic unequal reactivity and average molecular weights in non-linear stepwise polymerization

The general expressions of average molecular weights in the pre-gel region, for stepwise polymerization of polyfunctional monomers endowed with both A and B coreactive functional groups, are extended to systems where some or all of the B groups react at different rates. The method of calculation is always based on the propagation expectation and the presence of by-product in the reactions is taken into account.