Integrated electrostatically resonant scan tip for an atomic force microscope

Abstract

The atomic force microscope (AFM) has become a practical tool for mapping surface features with a resolution better than 10 nm. As such, in recent years the demand from industry for the AFM has increased significantly. For the AFM to be a practical instrument, however, its operation must be user friendly and its performance must be consistent. The essential element of an AFM is a microprobe which uses a cantilever mounted with a sharp stylus as a force sensor. For reproducible measurements, it is crucial that the physical dimensions of the cantilever and its stylus be consistent. Typical dimensions of the cantilever are 100–200 μm in length, 20–50 μm in width, and 0.5–1.2 μm in thickness. Typical stylus dimensions include a height of at least 3 μm and a radius of tip curvature of less than 100 nm. Silicon micromachining techniques were applied to fabricate microprobes with built-in alternating-current excitation of the polysilicon cantilevers in our previous work. This article presents a compatible process for the formation of a fine grained polysilicon stylus on the cantilever and an optical port for fiber-optic interferometry readout. The process demonstrates the feasibility of integrating both electronic drive and sensing circuitry onto the microprobe for future use in multichannel AFM systems.

Microelectromechanical scanning probe instruments for array architectures

“…The microfabrication of the cantilever, tip, and electrodes on the same chip eliminates many of the asymmetries which result from hand assembly of torsional cantilevers. Instead of the typical parallel plate capacitor configuration to sense outof-plane deflections of the cantilever, [10][11][12] we have chosen to use an out-of-the-plane, interdigitated electrode design. There are several advantages of this design.…”

“…8 Silicon micromachining technology without piezoelectric films has been used to produce force sensing cantilevers with actuation. [10][11][12] These cantilevers rely on parallel plate electrodes to provide an electrostatic force for actuation as well as a capacitance for deflection sensing. As the device size is scaled downward, however, the area of the electrodes decreases.…”

Electrostatically actuated double cantilever AFM probe for high speed imaging

“…One of the speed limiting factors in the conventional AFM systems is a piezoelectric element that tracks the tipsample interaction. Higher scanning rates can be obtained by substituting the external piezoelectric actuation with an active scanning probe with an integrated electrostatic microactuator [3][4][5][6][7][8].…”

A New Method to Fabricate Metal Tips for Scanning Probe Microscopy

“…A method of forming currently commercially available cantilevers is the process of a pyramidal Si3N4 tip formation by dissolving a silicon mold [2,3]. Previously reported processes involve wet, dry, or a combination of both dry and wet etching techniques, besides oxidation, to provide silicon tips [4][5][6][7][8], silicon dioxide tips [2], and polysilicon tips [9]. In order to use the tips in the AFM/STM, a conductive film is deposited on them.…”