Microelectromechanical scanning probe instruments for array architectures

Abstract

A compact (150 μm×150 μm), electrostatic actuator for out-of-plane (z) actuation of a probe tip has been designed, fabricated, and tested. Static deflections of ±0.7 μm out of the plane of the substrate have been achieved. The device consists of a single crystal silicon tip on a torsional cantilever with out-of-plane interdigitated electrode capacitors. This cantilever and electrode design allows a wide range of stiffnesses, actuator force, and frequency response. Significant improvements in performance (larger tip displacement and increased sense capacitance) and a higher density of devices per unit area can be obtained as the minimum feature size decreases. Applications such as information storage, molecular manipulation, and nanolithography require high density, parallel arrays for reasonable throughput. To demonstrate the suitability of this device for use in such arrays, a 12×12 array of microelectromechanical probe tips with integrated actuators and capacitive sensors for scanning probe microscopy has been fabricated. The size of each array element is about 150 μm by 150 μm with a tip-to-tip spacing in the array of 200 μm. Given these dimensions, the packing density of the devices is about 2500 units/cm2.