Demonstration of cone shaped Cu micro-bumps by nanoparticle deposition process

Cone shaped micro-bumps with Cu are successfully demonstrated with nanoparticle deposition process, which is previously used to deposit Au cone shaped bumps. The process employs helium gas to carry nanoparticles and sprays the nanoparticles onto patterned resist on target wafer. Then cone shaped bumps can be formed with self-forming by flow of the carrier gas. The paper presents formation process and basic characteristics of the bumps. The first integration result including electrical and mechanical characteristics are also presented.