Bu-Gao Xie

Electrodeposition of Mirror-Bright Silver in Cyanide-Free Bath Containing Uracil as Complexing Agent Without a Separate Strike Plating Process

A cyanide-free silver plating bath containing uracil as a complexing, agent was investigated. The electrochemical properties of a silver complex were studied on a disk glassy carbon electrode by means of cyclic voltammetry and a rotating disk electrode. The brightness and adhesion of silver deposits obtained from this silver plating bath onto copper substrates in the absence and presence of polyethyleneimine (PEI) were evaluated. Mirror-bright and good adherent silver deposits could be obtained without a separate strike plating process when PEI as an additive was added. Differential capacitance studies indicated that competition adsorption between PEI and uracil molecules occurred on the silver surface. The electrochemical displacement rate of silver by base metal (e.g., copper.) was very slow compared with that in it typical cyanide strike bath from the results of electrochemical quartz crystal microbalance studies. The surface morphology of silver deposits characterized by scanning electron microscopy illustrated that, with the addition of PEI, the grain size of the deposits decreased from hundreds to tens of nanometers

In Situ Monitoring of Additives in Copper Plating Baths by Cyclic Voltammetric Stripping with a Microelectrode

A microelectrode (ME) has been developed to replace rotating disk electrode (RDE) for in situ monitoring of additives in copper plating baths by cyclic voltammetric stripping (CVS). Details on the relationship between the dimension of ME and the rotation speed of RDE producing same mass transfer rate were described. The results in theory showed that the stationary ME can reach a very high mass-transfer coefficient which is comparable to that at RDE with high rotation rate. Comparison of CVS studies between ME and RDE showed that a good agreement was obtained in analyzing additives in a copper plating bath, containing chloride ions, polyethylene glycol, 3-mercapto-1 -propanesulfonate, and Janus Green B or some combination of them. The similar tendencies of curves for different additive packages indicated that effects of additives on copper electrodeposition are the same at both electrodes. Furthermore, results of sample analysis also showed positive evaluation to ME. It was proved that ME might be a substitute for RDE which monitors additive concentrations in copper and other metal plating baths.

Superconformal Electrodeposition of Silver from a Cyanide-free Bath for on-chip Metallization

A cyanide-free plating bath was used for the superconformal deposition of silver into fine trenches. It shows that in thiosulfate silver plating bath, cysteine as an additives adsorbed on silver electrode surface could enhance the polarization of silver deposition and suppress silver deposition rate. Trenches with 300 nm in width were void- freely filled in this bath.