抄録
In the past few decades, many micro-electromechanical systems (MEMS) devices have been developed. To encapsulate a tiny MEMS device into a microcavity, a sealing ring is often used. The sealing ring is fabricated on a cap wafer or on a MEMS substrate by Au electroplating. The electroplated Au surface is rough compared to polished wafer surface. Therefore, high temperature bonding process is often used in order to deform the Au and achieve intimate contact. However, it is expected that Au surface with much smaller roughness can form intimate contact at lower temperatures. In this work, we carried out the room temperature bonding using electroplated Au seal rings smoothed by two different methods. One is a surface smoothing by thermal imprint method using smooth substrate as a master mold. Other is a surface smoothing by lift-off method using a sacrificial layer. Moreover, hermeticity of bonding processes using these smoothed surfaces was evaluated by diaphragm structures, which were prepared by photolithography and dry etching of Silicon-On-Insulator (SOI) substrate. As a result, good hermetic sealing was confirmed using the replicated surface smoothed by lift-off process.
