| abstract |
Provided are methods and structures for good adhesion of intermetallic compounds (IMC) on Cu filler bumps. The method includes depositing Cu to form a Cu filler layer, depositing a diffusion barrier layer on top of the Cu filler layer, and depositing a Cu cap layer on top of the diffusion barrier layer, wherein the intermetallic compound (IMC ) Is formed between the diffusion barrier layer, the Cu cap layer and the solder layer on top of the Cu cap layer. The IMC has excellent adhesion on the Cu filler structure, the thickness of the IMC is controllable by the thickness of the Cu cap layer, and the diffusion barrier layer limits the diffusion of Cu from the Cu filler layer to the solder layer. The method may also include depositing a thin layer for improved wettability on top of the diffusion barrier layer prior to depositing the Cu cap layer. |