Formic acid treatment with Pt catalyst for Cu direct bonding at low temperature

The paper describes a new process of Cu-Cu direct bonding at a temperature lower than 200°C in atmospheric pressure. The method consists of reduction process of Cu oxide using formic acid treatment and subsequent generation of Cu nano-particles by means of Pt catalyst. The main idea of the proposed method is that due to Pt catalytic effect, combined to the conventional formic acid treatment, a part of the formic acid is decomposed to generate hydrogen radicals to reduce the oxide of the Cu surface, CuO and produce Cu formats very effectively. As the result, nano-particles of Cu are precipitated from the formats on the Cu surface and a tight bonded interface can be formed at a temperature below a 200°C. Cu surface was heated in water vapor to enhance the oxidation process and compared regarding to the precipitation of the Cu nano-particles.