<title>Fabrication of piezoresistive-sensed AFM cantilever probe with integrated tip</title>

Abstract

First piezoresistive AFM sensor developed by Quate was based on SOI technology. Alternative technology for fabrication of microtips integrated with silicon cantilever beam, used as a microprobe in atomic force microscopy, is described in this paper. It is based on a bulk micromachining to define the cantilever thickness, surface micromachining to develop sharp tip and standard IC planar processing. Specific sequence of plasma treated photoresist and hard masking steps followed by wet isotropic, wet anisotropic and dry etching is utilized to obtain very sharp silicon tips. First, HF/HNO<SUB>3</SUB> based polishing etchant is used to create mesa islands at the end of the formed cantilever. Next, a planar IC processing sequence is realized to fabricate piezoresistive Wheatstone bridge which will serve as a force sensing element. Thickness of the beam is precisely controlled by electrochemical etch-stop technique in. Then, sharp tip is formed by both RIE and/or wet etching, using under-cutting method. Finally, deep anisotropic silicon etching combined with SF<SUB>6</SUB>/Ar plasma etching is used to create cantilever silicon beam.