1999RFC

周柔甫 (Rou Fu Chou)

Design and Fabrication of Planar Scanning Probes

平面型微細探針的研究

In this research, two types of planar scanning probes are designed and analyzed.

The structure of the scanning probe includes a cantilever beam with a sensing tip. The tip is formed by the intersection of three crystal planes during wet anisotropic etching. Two types of scanning probes with different sensing principles are proposed here. One is integrated with a piezoresistor at the root of the cantilever beam. When the cantilever beam is bending, the variation of the resistance of the piezoresistor transfers to voltage signal by Wheatstone bridge circuit. Then the magnitude of the stress on the cantilever beam can be calculated and the displacement of the beam can be determined. The shape of the cantilever is designed as a triangle to have a uniform stress distribution on the surface. The dimensions of the cantilever beam are 200μm × 40μm × 4μm.

Another probe use an external optical sensing component to detect the angle difference of the reflective laser light which can determine the displacement of the cantilever beam. The dimensions of the cantilever beam are 250μm × 45μm × 4 μm.

An additional capacitive actuator can be integrated to the scanning probe by electroplating and sacrificial layer techniques. In fabrication, the traditional bonding technology is not needed here to form the electrostatic capacitor. Thick photoresist is coated on the cantilever beam to form a sacrificial layer and nickel is followed to be an electrode for the electrostatic actuator by electroplating. The function of the capacitive actuator is to control the tiny displacement of the cantilever beam or to excite the cantilever beam for resonance.