SOI on buried cavity patterns using ion-cut layer transfer

Summary form only given. Silicon-on-insulator (SOI) on top of buried cavity structures offer many new applications in the fields of micro-sensors and actuators, micro-fluid delivery systems, and micro plasma display arrays. In active device circuits integrated with the sensors, the presence of patterned air-gaps can also lower the overall substrate and interconnect capacitance, allowing higher speed circuit operation. Existing methods of fabrication of such structures are usually based on a bonding-and-etchback technique with different etch stop methods. In many micro-electromechanical system (MEMS) applications, precision of over-layer thickness, thickness uniformity between devices, and surface microroughness are critical. The etch stop approach based on epitaxy or deep implants addresses some of the control concerns, but adds process complexity and manufacturing cost. In this paper, we report the demonstration of an effective method of forming SOI membranes over patterned cavities using the ion-cut silicon layer transfer process. The basics of this process consist of ion implantation of hydrogen into a donor wafer, followed by low temperature direct wafer bonding to the receptor wafer that has patterned trenches of various shapes and sizes. The bonded wafer pair is then heated until spontaneous silicon layer cleavage occurs along the depth corresponding to the implanted hydrogen peak concentration.