Fabrication of z-axis accelerometer with galvanic etch stop and antifuse isolation

This paper reports a release-after-package process to fabricate a fully symmetrical sandwich z-axis accelerometer with galvanic etch stop, which employs antifuse isolation to suppress the leakage current during etching. The sandwich structure is composed of three silicon layers. The suspension beams and the electrodes are made on the top and bottom layer. The proofmass and supporting rim are made on the middle layer. The structure is formed and released by galvanic etch stop after partially packaging to increase the yield. As the leakage current may induce unwanted etch stop of sacrificial area, antifuses are used to connect the beams and mass. The antifuses are kept off-state during TMAH etching, so that the middle layer is selectively etched to form the mass while the top and bottom layers are protected by galvanic cell. After the structure is released, the antifuse is breakdown to on-state to connect the beams and mass electrically. Two structures have been fabricated with the technique.