A new compensation method for the footing effect in MEMS fabrication

Abstract

A new compensation pattern method to eliminate the footing effect on MEMS devices was proposed using the buffer structure in silicon deep RIE (reactive ion etching). The buffer structure gets the entire footing effect instead of the desired structure and then it is removed after the deep RIE process. The compensation pattern was devised from the characteristics of the RIE lag and the footing effect. The silicon inside the buffer structure is etched to the sacrificial layer and the footing effect first occurs at that moment. The desired structure is not etched to the bottom layer at that moment because of the RIE lag. The etch process is terminated when the desired structure is patterned. The proposed method makes it possible to remove the footing effect in the deep RIE process by modifying the mask layout without changing the fabrication processes. The sense capacitances were approximately 1.7 times higher than that of conventional devices, which verified the effectiveness of the proposed method.