No abstract

Abstract-This paper presents the design, modeling, and fabrication of a planar three-degrees-of-freedom parallel kinematic manipulator, fabricated with a simple two-mask process in conventional highly doped single-crystalline silicon (SCS) wafers 100 . The manipulator's purpose is to provide accurate and stable positioning of a small sample (10 × 20 × 0.2 μm 3 ), e.g., within a transmission electron microscope. The manipulator design is based on the principles of exact constraint design, resulting in a high actuation-compliance combined with a relatively high suspension stiffness. A modal analysis shows that the fourth vibration mode frequency is at least a factor 11 higher than the first three actuation-related mode frequencies. The comb-drive actuators are modeled in combination with the shuttle suspensions gaining insight into the side and rotational pull-in stability conditions. The two-mask fabrication process enables high-aspect-ratio structures, combined with electrical trench insulation. Trench insulation allows structures in conventional wafers to be mechanically connected while being electrically insulated from each other. Device characterization shows high linearity of displacement wrt voltage squared over ±10 μm stroke in the x-and y-directions and ±2• rotation at a maximum of 50 V driving voltage. Out-of-plane displacement crosstalk due to in-plane actuation in resonance is measured to be less than 20 pm. The hysteresis in SCS, measured using white light interferometry, is shown to be extremely small.[ 2009-0254]Index Terms-Compliant mechanism, electrostatic actuators, exact constraint design, multidegrees of freedom, nanometer positioning, precision engineering, trench isolation.

In this paper the design, modeling and fabrication of a precision MEMS-based clamp with a relatively large clamping force are presented. The purpose of the clamp is to mechanically fix a six-degree-of-freedom (DOF) MEMS-based sample manipulator (Brouwer et al J. Int. Soc. Precis. Eng. Nanotechnol. submitted) once the sample has been positioned in all DOFs. The clamping force is generated by a rotational electrostatic comb-drive actuator and can be latched passively by a parallel plate type electrostatically driven locking device. The clamp design is based on the principles of exact constraint design, resulting in a high actuation compliance (flexibility) combined with a high suspension stiffness. Therefore, a relatively large blocking force of 1.4 mN in relation to the used area of 1.8 mm 2 is obtained. The fabrication is based on silicon bulk micromachining technology and combines a high-aspect-ratio deep reactive ion etching (DRIE), conformal deposition of low-pressure chemical vapor deposition (LPCVD) silicon nitride and an anisotropic potassium hydroxide (KOH) backside etching technology. Special attention is given to void reduction of Si x N y trench isolation and reduction of heating phenomena during front-side release etching. Guidelines are given for the applied process. Measurements showed that the clamp was able to fix, hold and release a test actuator. The dynamic behavior was in good agreement with the modal analysis.

A design is presented for a large force (0.5 mN) high precision MEMS clamping mechanism. The clamp is part of a MEMS TEM sample manipulator, which needs to be fixed un-powered once positioned. The elastic deformation of the clamp suspension has been optimized to not influence the TEM sample manipulator position during clamping. The dimensions of the elastic elements have been further optimized for minimal elastic energy storage, minimizing force for deformation and thus the device area. Fabrication involves a back-etch release process, offering great design freedom, resulting in a compact and optimal design.

We present the first monolithic manipulator for in-plane positioning in three degrees of freedom (DOF), based on a parallel flexure-mechanism. The manipulator stage is capable of translation in the x-and y-direction (maximum of ±9 µm) as well as rotation about the z-axis (maximum of ±2 degrees). A power-port based model has been developed to give insight in the systems behavior. The effect of anisotropy in the Young's modulus of single crystalline silicon (SCS) on the flexure stiffness is modeled and matches the real system.