A New Low-cost Approach to Fabricate Silicon Dioxide for Insulator of Through-Silicon-Via

Through-silicon via (TSV) is a critical technology for electrical connection in 3D integration and the formation of insulating layer is one of the most critical steps which directly influence the reliability of TSV package. In this article, silicon dioxide is obtained by a new method based on the formation of the porous silicon (PS). In this experiment, the HF solutions with the concentrations of 2.5wt%, 10wt%, 20wt%, and 25wt% are applied to form porous silicon on P-type Si wafer respectively. The microstructure of PS is characterized by scanning electron microscope (SEM). Because of the thin pore wall and large specific surface area, PS is much easier to be completely oxidized. As a consequence, the oxidizing temperature can be reduced to 600 degrees C in dry oxygen. Moreover, in order to further reduce the oxidizing temperature and the cost, the electrochemical oxidization of PS is also investigated. Then PS is anodized on the voltage of 5.5V at room temperature for thirty minutes, the EDS results indicate that the atomic ratio of Si/O is approximately 0.5 in the whole porous silicon region. That means the porous silicon layer is totally oxidized into silicon dioxide.