Application Oriented Micro-Nano Electro Mechanical Systems

Micromachining is an extended IC fabrication based on photo-fabrication, deep etching, anodic bonding and other advanced process technologies. This is used to produce MEMS (Micro Electro Mechanical Systems) featuring multi-functions, small size and low cost. Nanostructures such as CNT (Carbon Nano Tube) can be also included in the MEMS by nanomachining. MEMS are used as value added key components in systems. Examples of application oriented MEMS developed with attention to packaging and circuit integration will be described below. Silicon rotational gyroscope has been developed for the purpose of motion control and navigation. The principle and the photograph are shown. A 1.5 mm diameter silicon ring which is electrostatically levitated by digital control using capacitive position sensing and electrostatic actuation is rotated at 75,000 rpm. The rotation is based on the principle of a variable capacitance motor. A 5mum radial gap between the ring rotor and stator electrodes is formed using deep RIE (Reactive Ion Etching) of a silicon wafer. The silicon is anodically bonded on both sides to glasses which have electrodes. The chip is packaged in a vacuum cavity to prevent a viscous dumping. This inertia measurement system can measure two axes rotation and three axes acceleration simultaneously with high precision (sensitivity 0.01 deg/s and 0.2mG respectively).