Cu electrochemical mechanical planarization ͑ECMP͒ is currently being investigated to replace or supplement Cu chemical mechanical planarization ͑CMP͒ due to the introduction of porous low-k dielectric materials, which may not withstand the mechanical force applied during conventional CMP. Electrolytes for Cu ECMP at pH 3 containing 5-phenyl-1-H-tetrazole ͑PTA͒, hydroxyethylidenediphosphoric acid, and oxalic acid are investigated using electrochemical methods and polishing of Cu-coated blanket and patterned wafers. The Cu removal rate and the planarization efficiency during Cu ECMP can be approximated using electrochemical measurements of the Cu removal rate, with and without surface abrasion. These results predict a 500 mV potential window within which the Cu removal rate is greater than 600 nm/min and the planarization efficiency is greater than 0.90. However, high planarization efficiencies are only obtained when silica abrasives are included within the ECMP electrolyte. In situ electrochemical impedance spectroscopy results indicate that the interfacial impedance is increased by the presence of silica, suggesting that silica is incorporated into the PTA-based passive film and is thus needed for effective planarization. Electrochemical quartz crystal microbalance experiments indicate that PTA may provide better Cu surface passivation at a high anodic potential than benzotriazole, which is widely used during Cu CMP.

A new type of nanopore sensor design is reported for a reagent-less electrochemical biosensor with no analyte "tagging" by fluorescent molecules, nanoparticles, or other species. This sensor design involves immobilization within Au-coated nanopores of bacterial periplasmic binding proteins (bPBP), which undergo a wide-amplitude, hinge-twist motion upon ligand binding. Ligand binding thus triggers a reduction in the effective thickness of the immobilized protein film, which is detected as an increase in electrolyte conductivity (decrease in impedance) through the nanopores. This new sensor design is demonstrated for glucose detection using a cysteine-tagged mutant (GGR Q26C) of the galactose/glucose receptor (GGR) protein from the bPBP family. The GGR Q26C protein is immobilized onto Au nanoislands that are deposited within the pores of commercially available nanoporous polycarbonate membranes.

P3-Na0.9Fe0.5Mn0.5O2 is reported as a new P-type cathode material for Na-ion batteries. P3 structure can accommodate 0.9 mole of Na-ions leading to high discharge capacity of 155 mAh/g and does...

The introduction of porous low-k dielectric materials into semiconductor devices requires the development of low downforce Cu chemical mechanical planarization ͑CMP͒. An alternative passivation agent, 5-phenyl-1H-tetrazole ͑PTA͒, is proposed here that is effective at lower pH than the traditional CMP passivation agent, benzotriazole ͑BTA͒. PTA has previously been reported as a low-pH Cu corrosion inhibitor, but has not been explored for Cu CMP. Cu CMP removal rates and Cu static etch rates are measured for slurries containing 3 wt % H 2 O 2 , 1 wt % glycine, 3 wt % colloidal silica, and PTA concentrations ranging from 0.5 to 3 mM. At pH 3 and PTA concentrations of 0.5-2 mM, PTA provides both effective passivation and Cu removal rates of Ͼ1400 nm/min. Fourier transform-infrared and electrochemical studies are consistent with the formation of an effective passivation layer on Cu in CMP slurries containing PTA concentrations ranging from 0.5 to 2 mM, with the effectiveness of passivation increasing with PTA concentration. The improved low-pH passive film formation for PTA in Cu CMP slurries relative to BTA is most likely due to its much lower pKa ͑4.3͒, with a much larger fraction of PTA in the anionic form at low pH.