Porous Anodic Aluminum Oxide Interposer: Fabrication, Characterization, and Evaluation

Porous anodic aluminum oxide (AAO) has been proposed to be interposer substrate material in recent years. This work is to deliver fabrication and characterizations results of AAO film itself and test structures then, finally, evaluate its possibility to be an interposer material. First, chemical durability test was done in 4 solutions which indicated fabricated AAO was relatively weak against base and acidic solutions which could be improved by adding additional annealing process. Electrical measurements were conducted to probe daisy chain up to 400 nodes, coplanar waveguides (CPW), and embedded solenoid inductors. Data showed linear relationship between numbers of vias and resistance in daisy chain DC measurements; insertion loss from CPW measurement suggested less than 0.2 dB (0.167 dB/mm) insertion loss from 45 MHz all the way to 20 GHz. Embedded solenoid inductors in the current design had quality factor (Q) reaching 41 in 2-turn inductor design. AAO can be a potential interposer material based on our fabrication process and characterization results. (C) 2019 The Electrochemical Society.