Study for Bonding Technology by Electroplated Nano porous Cu Structure

Abstract

The various kinds of the packaging technologies such as 2.nD, 2.5D, 3D are highly studied with the rapid development of miniaturization and high density of semiconductor packaging. This trend increases the importance of fine pitch interconnect. To achieve fine pitch interconnect, Cu-Cu direct bonding or hybrid bonding which has no solder in bonding layer is the promising technologies. There are some difficulties in the solderless bonding such as the control of bump uniformity, high accuracy CMP (Chemical Mechanical Polishing) process and so on. In particular, the exact surface shape control is the essential issue. To solve these problems, we are proposing Nano porous (NP) Cu materials for interconnect material. One of the technical challenges is the process for formation of NP Cu µ-bump structure. We are focusing on electroplating process for µ-bump formation. Firstly, we developed the plating chemicals for formation of NP Cu structure. We consider two types of plating chemicals for NP Cu formation, de-alloying and direct porous plating process. For de-alloying process, Cu-Zn alloy bumps were plated, and NP Cu bumps were obtained by de-alloying the Cu-Zn alloy. For direct porous plating process, NP Cu bumps were plated by using unique additives which can form NP structure directly. By using electroplated NP Cu, we studied its various properties, and carried out bonding tests. As the results, NP Cu structure shows unique properties such as electrical conductivity and the hardness, and we consider that these unique properties should widen the bonding process margin. We would like to present our recent research of NP Cu which is promising materials for advanced bonding technology.