Mechanism of Nodule Formation in Electroless Copper Deposition

Abstract

We have investigated the extraneous nodule deposition phenomenon in the formation of circuit pattern by electroless copper plating. The nodules are spherical and the sphere centers are on the resist wall. Small nuclei on the resist wall cause the electroless plating reaction. Small non-conductive particles like metal-oxides can act as the deposition nuclei. The growth of such nuclei is affected by diffusion of disolved oxygen. Measurement of diffusion parameters gives the critical size of a nucleus for nodule formation. We have made clear that particles result in nodule formation in the case of bigger than 4.2μm and located on the resist wall.