Batch processing of CMOS compatible feedthroughs

This paper presents a technique for batch fabrication of electrical feedthroughs in CMOS wafers. The presented process is designed with specific attention on industrial applicability. The electrical feedthroughs are processed entirely by low temperature, CMOS compatible processes. Hence, the process scheme allows for post processing of feedthroughs in any kind of fully processed CMOS wafer. The fabrication of the electrical feedthroughs is based on wet etching of through-holes, low temperature deposition of dielectric material, and electrodeposition of photoresist and feedthrough metal. The feedthrough technology employs a simple solution to the well-known CMOS compatibility issue of KOH by protecting the CMOS side of the wafer using sputter deposited TiW/Au. The fabricated feedthroughs exhibit excellent electrical performance having a serial resistance of 40 mΩ and a parasitic capacitance of 2.5 pF.