This thesis is about a “Micromachined capacitive long-range displacement sensor for nano-positioning of microactuator systems��?. Possible applications of such microsystems are found in future probe-based datastorage, scanning probe microscopy, microbiology, optical lens manipulation, microgrippers and microrobots, etc. These applications require positioning with nanometer precision over a long range (ten’s of micrometers) and benefit from further miniaturization and the application of sub-mm sized Micro Electro Mechanical Systems (MEMS). In many cases open-loop operation is not sufficient and a form of system control is required to combine nanometer accuracy with a large dynamic range and to obtain better system performance. In order to make such systems both economically viable as well as compact, on-chip position sensing appears to be a requirement. The aim is therefore, to obtain optimal performance through an integration of sensor and actuator with micromachining fabrication technology without additional micro assembly. The target specifications for the microsensor were to obtain 1-10 nm accuracy in a range of 100 μm or more i.e. dynamic measurement range of 10^5 or more. For experimental assessment various devices with various periodic geometries were designed for a surface micromachining process. The design integrates electrostatic actuators with a capacitive position sensor in a 5 μm-high poly-silicon structural layer, using one mask. The capacitance between the two geometries on sense-structures and slider is converted to a voltage and measured using a charge amplifier and a synchronous detection technique. For Constant Capacitance Measurement Mode an estimated position uncertainty below 10 nm is demonstrated, although far from real-time operation. However, a position uncertainty of 1 nm or less appears feasible.
- Capacitive sensors
- nano positioning