Electroless Copper Deposition Using Saccharose Containing Copper Methane Sulphonate Bath with Thiourea as Stabilizer

Abstract

Electroless copper deposition is used in the fabrication of integrated circuit (IC) interconnections, micro-electro-mechanical systems (MEMS) devices and printed circuit board (PCBs). In order to meet the long term usage of chemical bath for electroless deposition, an ecofriendly copper methane sulphonate (CuMS) was used to prepare the chemical bath for Cu deposit. The deposition parameters such as temperature, pH, Cu ion concentration and para-formaldehyde concentration were optimized at 28 °C with 3 g/L of CuMS, 10 g/L of para-formaldehyde for the pH of 12.75.The deposition rate was increased for high concentration of Cu and para-formaldehyde in the chemical bath. Highly stable bath was achieved at 28 °C with 1 ppm thiourea content and produced uniform Cu film surface with larger grains. Good quality and (200) oriented Cu thin film with larger crystallite size was observed with 1 ppm thiourea added bath.