Effect of HEDTA on the Adsorption of 2,2 Bipyridyl and 3-Mercaptobenzothiazole and Electroless Cu Deposition Rate

Abstract

Surface-enhanced Raman spectroscopy (SERS) and chronoamperometry were utilized to evaluate the electroless deposition of Cu in hydroxyethylethylelenediaminetriacetic acid (HEDTA)- and tartrate-based baths containing 2,2’-bipyridyl (BP) and 2-mercaptobenzothiazole (MBT). The Cu deposition rate was shown to be faster in tartrate baths, with rates at 0.08 µm/min without MBT or BP but decreased to near zero with concentrations approaching 6 µM of either MBT or BP. HEDTA baths displayed a slower rate of 0.04 µm/min without MBT or BP. However, the addition of MBT increased the rate up to 4-fold, while BP concentration did not affect the deposition rate. SERS data showed that HEDTA adsorbs to the surface while tartrate does not. Kinetic Langmuir isotherm model fits showed a decrease in MBT and BP adsorption rate in the presence of HEDTA and showed a decrease in HEDTA adsorption upon MBT injection while BP injection did not affect the HEDTA adsorption. Competition between the complexing and the stabilizing agent is a key factor for the rate of electroless Cu deposition.