Micromachined force-balance feedback accelerometer with optical displacement detection

An apparatus comprising:

• a proof mass and a frame in a handle layer of a silicon-on-an-insulator (SOI), the proof mass separated from the frame by a back-side trench that defines a boundary of the proof mass;
• a reflector at a device side of the SOI and coupled to a top surface of the proof mass;
• an optical detector located above the reflector at the device side;
• and
• at least one suspension spring having a handle anchor that extends downwards from the device side to the handle layer to mechanically support upward and downward movement of the proof mass relative to a top surface of the proof mass.

A system comprising:

• a handle layer, which comprises:
• a proof mass and a frame, the proof mass separated from the frame by a back-side trench that defines a boundary of the proof mass;
• and
• a device layer coupled to the handle layer via a buried oxide layer, the device layer comprising:
• a reflector;
• an optical detector;
• a plurality of suspension springs, each of the suspension springs having a handle anchor that extends downwards to the handle layer to mechanically support upward and downward movement of the proof mass relative to a top surface of the proof mass;
• a plurality of up actuation electrodes to receive a first voltage that controls the upward movement of the proof mass;
• and
• a plurality of down actuation electrodes to receive a second voltage that controls the downward movement of the proof mass.