Fabrication and Characterization of Vanadium Doped PbZr_0.53Ti_0.47O₃ (PZTV) Force Sensors for Minimally Invasive Surgical Tools

Abstract

Minimally invasive surgery (MIS) is the most exciting and rapidly developing area where force sensing is actually of central importance. Micro-machined piezoelectric sensors can be integrated onto MIS tools for improved diagnosis and treatment monitoring. A micro-machined freestanding vanadium doped-lead zirconate titanate (PZTV) force sensor is fabricated using five masks process incorporating deep reactive ion, ion beam and wet-chemical etching techniques. The PZTV sensor is designed as a parallel plate capacitor structure in which the sol-gel prepared 1-μ m thick PZTV film is sandwiched between top (Au/Cr) and bottom (Pt/Ti) metal electrodes mounted on a thin Si membrane. This paper also describes a new wet chemical approach for patterning vanadium doped-PbZr_0.53Ti_0.47O₃ films. The etch recipe provided excellent etch control, minimized undercut, preserved the photoresist mask, and effectively removed the residues on the etched surfaces. A high etch rate (200 nm/min), high selectivity with respect to photoresist, and limited under-cutting (1.5:1, lateral : thickness) were obtained. The fabricated force sensor exhibited good ferroelectric properties. The current fabrication procedure and electrical analysis can be considered as a breakthrough for fabricating freestanding PZT force sensor in any desired shape and dimensions, as well as a good example of ferroelectric microdevices.

Acknowledgment

The author would like to thank Republic Polytechnic and TOTE board, Singapore for their kind support under the research grant M16.