Studies on the action of mercapto azole additives on the coating and bath characteristics of autocatalytic copper nano film deposition

This article aims at analyzing the influence of structurally related two azole additives such as 2-
Mercaptobenzothiazole (2-MBT) and 2-Mercaptobenzimidazole (2-MBI) in the rate of autocatalytic
copper nano film depositions. The effect of these stabilizers on the characteristics of both the
electroless plating bath and electroless copper deposition is also studied. Dimethylamine borane
(DMAB) is employed as the reducing agent and sorbitol as complexing agent in the copper
methanesulphonate bath. Potassium hydroxide acts as the suitable pH regulator to modify the properties
of copper nano deposits. 1 ppm of the azole additives are added in this eco-friendly bath and optimized
at a pH of 12.75 ± 0.25 at a temperature of 28±2 °C. The results obtained from various studies imply
that 2-MBT had an inhibiting effect on copper deposition, whereas 2-MBI accelerated the deposition
rate. The physical properties like deposition rate, thickness and activation energy are calculated to
support the stabilizing effects of 2-MBT and 2-MBI. Surface morphology of the copper deposits is
characterized by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM)
techniques. Structural properties such as crystallite size and specific surface area of plain bath and
additives laden baths are investigated using X-ray diffraction studies.