Bonding on Cu: a new stress evaluation approach by Raman spectroscopy

The first purpose of this paper is to show that bonding of Cu wires on top of Cu pads is possible. This technique greatly reduces the back-end costs because less processing steps are required. However, since Cu is harder than Al or Au, it is expected to generate higher mechanical stresses and more bonding problems to the Si substrate during and/or after wire bonding. So, the second purpose of this paper is to present a new approach to analyze the stress induced by the bonding in the Si near and under the Cu pads by use of Raman spectroscopy and a new analytical model.