Fabrication of multipurpose piezoresistive Wheatstone bridge cantilevers with conductive microtips for electrostatic and scanning capacitance microscopy

The fabrication and performance of a microprobe with multipurpose capabilit ies for scanning probe microscopy is presented in this article. Atomic forc e microscopy (AFM), scanning capacitance microscopy, and electrostatic forc e microscopy measurements can be simultaneously performed with the probe in which a silicon tip is integrated with a piezoresistive cantilever. Fabric ation of the microprobe is based on double side bulk/surface micromachining of silicon on insulator (SOI) substrates. The novelty of this device is a highly doped silicon tip with a curvature radius of about 20 nm which is el ectrically isolated from the silicon cantilever by the buried oxide layer o f the SOI substrate. At the beam supporting point a piezoresistive Wheatsto ne bridge is fabricated to allow the deflection of the microtip to be monit ored. This cantilever displacement detection system enables measurements in vacuum and simplifies the design of the AFM head. Experimental measurement s agree well with theoretical estimates of the sensitivity of the microprob e. (C) 1998 American Vacuum Society. [S0734-211X(98)18506-2].