Approaches for a Solely Electroless Metallization of Through-Glass Vias

With the ever increasing demand for miniaturization in microfabrication, three dimensional integration is considered the key for progress and reliable vertical interconnect accesses (vias) are crucial. Glass substrates are potent alternatives for silicon in 3-D technologies with their comparable characteristics, their advantage of inherent isolation, and low insertion losses. Through-Glass Vias (TGVs) are commonly metallized using PVD, CVD, or electroless deposition for a seed layer followed by the electrodeposition of copper. Inspired by molded interconnect devices (MID) technologies, the goal of this paper is a solely electroless TGV filling on the basis of three priming approaches: self-assembling monolayers of (3-mercap-topropyl) trimethoxysilane (MPTMS), a photocatalytic layer of titanium tetraisopropoxide (TTiP) and a sol-gel process. Priming with a TBuT solution proved to be particularly suitable. This coating has high-temperature resistance, good adhesion in the TGVs, and allows a solely electroless filling with a layer stack of NiCuNiAu and CuNiAu.