Fabrication of void-free copper filled through-glass-via for wafer-level RF MEMS packaging

A novel fabrication method of copper filled through-glass-via is presented for wafer-level RF MEMS packaging. By using glass reflow and seedless electroplating process, a void-free copper via with a smooth side wall can be obtained. This enables a vertical interconnection between the electrical pads through the glass substrate. Furthermore, the proposed through-glass-via was applied to the packaging of a CPW transmission line to investigate its effects on the RF performances. For the encapsulation of the packaged device, which is the CPW line in this case, the glass cap with the cavity is anodically bonded to the substrate. The measured insertion loss of the whole packaging including the copper vias and the CPW line covered with the glass cap was 0.197 dB and the return loss was 20.032 dB at 20 GHz.