High-stroke silicon-on-insulator MEMS nanopositioner: Control design for non-raster scan atomic force microscopy

Abstract

A 2-degree of freedom microelectromechanical systems nanopositioner designed for on-chip atomic force microscopy (AFM) is presented. The device is fabricated using a silicon-on-insulator-based process and is designed as a parallel kinematic mechanism. It contains a central scan table and two sets of electrostatic comb actuators along each orthogonal axis, which provides displacement ranges greater than ±10 μm. The first in-plane resonance modes are located at 1274 Hz and 1286 Hz for the X and Y axes, respectively. To measure lateral displacements of the stage, electrothermal position sensors are incorporated in the design. To facilitate high-speed scans, the highly resonant dynamics of the system are controlled using damping loops in conjunction with internal model controllers that enable accurate tracking of fast sinusoidal set-points. To cancel the effect of sensor drift on controlled displacements, washout controllers are used in the damping loops. The feedback controlled nanopositioner is successfully used to perform several AFM scans in contact mode via a Lissajous scan method with a large scan area of 20 μm × 20 μm. The maximum scan rate demonstrated is 1 kHz.

A switched actuation and sensing method for a MEMS electrostatic drive

“…The nanopositioner utilized in this work was published by Maroufi et al [19]. An image of the nanopositioner is shown in Figure 1.…”

“…This article outlines the design of a switched self-sensing technique for an electrostatic drive. It is applied to the MEMS nanopositioner published by Maroufi et al [19]. Section II introduces the MEMS nanopositioner used in this work, provides modeling for the device and identifies the model parameters.…”

Fast Specimen Boundary Tracking and Local Imaging with Scanning Probe Microscopy

“…Therefore, significant research efforts have been invested to minimize the scanning time by either improving SPM hardware or scanning algorithms, for example, specially designed optical beam deflection setup [ 4 , 5 ], innovative mechanical body design [ 6 , 7 ], high resonance frequency [ 8 – 11 ] or wide-area [ 12 ] nanopositioners, advanced modern control techniques, such as feedforward/feedback controller [ 13 – 15 ], active damping algorithm [ 16 ], and dynamic proportional-integral-differential controller [ 17 ], for the piezo actuators to eliminate the mechanical resonant vibrations in high-speed imaging. On the other hand, several interesting methods are developed for high-speed scanning with smooth scanning trajectories without modification in hardware such as sinusoidal waveform [ 18 , 19 ], spiral scanning [ 20 , 21 ], cycloid-like scanning [ 22 ], and Lissajous scanning paths [ 23 , 24 ].…”

Note: A silicon-on-insulator microelectromechanical systems probe scanner for on-chip atomic force microscopy

“…5 and closed loop with both raster 6,7 and non-raster trajectories. 8 However, whereas these previous results used the cantilever of a conventional AFM to obtain the deflection data used to generate the obtained images, this paper presents a new 2-degree-of-freedom (DoF) MEMSbased probe scanner that features an integrated piezoelectrically actuated cantilever suitable for directly measuring the topography of a sample. This is a significant step towards the complete replacement of a conventional macroscale AFM with a fully microfabricated system.…”

“…The mass of the comb structures is reduced while maintaining their mechanical stiffness through the use of a trapezoidal geometry. 8 Two sets of comb drives are implemented on each side of the stage in the x direction. For each set, the actuation force is transferred to the stage using a shuttle beam via two tethering beams.…”