Investigation of All Wet Chemical Process for the Barrier Formation in High Aspect Ratio Silicon Vias

The fabrication of through silicon vias with high aspect ratio is one of the key technologies for the miniaturization of 3-D integration systems. Cu as filling metal in vias can diffuse into the Si substrate of interposers and, therefore, reduce the reliability of the electronic components during their operation. Co alloys are considered to be the promising barrier materials preventing Cu diffusion. The deposition process of the Co alloys should be cost effective and capable of forming a thin uniform barrier layer over via walls. In this paper, a wet chemical method to deposit Co-Re-P as a barrier layer and a novel analytical technique for investigating the self-assembling molecules on the surfaces of blind-hole vias are reported. A three-step process consisting of silanization, nucleation, and electroless deposition of a Co-Re-P barrier layer is proposed. The composition of the Cu/Co-Re-P/SiO
₂
/Si layers after annealing is studied by glow discharge optical emission spectrometry. The prepared barrier layer can effectively prevent the diffusion of Cu into Si at temperatures up to 350°C. Moreover, the layer can be deposited in vias with an aspect ratio ≥10 by means of an acceleration-enhanced buoyancy method.