Focused ion beam tuning of in-plane vibrating micromechanical resonators

Vibrating resonators are important components of micromechanical systems, with applications in sensors and actuators. However, defects and stresses can cause resonance shifts, and it is important to develop methods of tuning. Passive methods are based on dimensional trimming and active methods on electrically-induced stress. For example, reactive ion etching (RIE) has been used to apply global dimensional changes [1], while focused ion beam (FIB) machining has been used locally to alter a resonant mass [2]. Stresses have been applied electrostatically [3, 4] and electrothermally [5] to elastic suspensions. Passive trimming is more economical, since it avoids the need for control circuitry. However, care is needed to optimise the tuning process.