Quasi-monolithic integration of silicon-MEMS with piezoelectric actuators for high-speed non-contact atomic force microscopy

Abstract

High-speed atomic force microscopy (AFM) is actually a functional tool for the studies of dynamical phenomena of biological and chemical objects on a sub-second timescale. In order to increase the imaging speed, all dynamic components of AFM have to be optimized. This paper presents advancement in the development of a novel x–y scanner for high-speed non-contact AFM. We have developed a quasi-monolithic integration of a silicon parallel kinematic mechanism with piezoelectric actuators. Decoupling of motion in x–y directions is realized due to novel Ω-shaped flexures. For the control of the stage motion, we employed piezoresistive sensors integrated into silicon L-shaped guidance features. Due to the use of a push–pull actuation principle, we obtained a large scanning frequency and a 6 × 6 µm2 scanning area. The resonance frequency of the stage is about 26 kHz. The silicon stage facilitates fast quantitative imaging with high lateral resolution.

A High-Bandwidth MEMS Nanopositioner for On-Chip AFM: Design, Characterization, and Control

“…In [15], a high bandwidth (26 kHz), low cross coupling quasi-monolithic XY nanopositioner is proposed. Piezoeresistive sensors are incorporated in the device to allow for real-time measurement of the stage displacement in both directions.…”

“…Piezoelectric and electromagnetic actuation are two other possibilities. However, their incorporation into a MEMS device would require postprocessing that adds to the complexity and cost of the device [15].…”

Displacement Sensing With Silicon Flexures in MEMS Nanopositioners

“…The proposed differential approach utilizes orientations of the suspension beams to exert opposite stresses on the piezoresistor pair rather than the differential method in [8], where piezoresistors have similar stresses and an interface circuit cancels the feedthrough signal from actuator to sensor. In contrast to the traditional sensors that use stresses generated on the surface of implanted piezoresistors [10]- [12], we employ the inherent axial forces generated in the existing suspension beams. This removes the need for doping certain zones to generate the piezoresistive effect.…”

MEMS Nanopositioner for On-Chip Atomic Force Microscopy: A Serial Kinematic Design

“…However, recent efforts to build a single-chip AFM have led to the emergence of a number of micro-sized nanopositioners realized through microelectromechanical systems (MEMS) fabrication processes [4], [7]- [9]. In addition to a small form factor, MEMS nanopositioners are potentially able to offer a variety of advantages over their macro-sized counterparts such as batch fabrication capability and a higher achievable bandwidth, mainly due to the adoption of silicon as the structural material [10].…”

“…An SKM can be realized by stacking one kinematic chain within another, while in a PKM, both kinematic chains are connected directly to the scanner table. Almost all MEMS nanopositioners reported in the literature for AFM applications follow a parallel kinematic design [4], [7], [8], [10]. This design approach, however, is known to lead to certain drawbacks.…”