Design of a high-speed, meso-scale nanopositioners driven by electromagnetic actuators

Abstract

The purpose of this thesis is to generate the design and fabrication knowledge that is required to engineer high-speed, six-axis, meso-scale nanopositioners that are driven by electromagnetic actuators. When compared to macro-scale nanopositioners, meso-scale nanopositioners enable a combination of greater bandwidth, improved thermal stability, portability, and capacity for massively parallel operation. Meso-scale nanopositioners are envisioned to impact emerging applications in data storage and nanomanufacturing, which will benefit from low-cost, portable, multi-axis nanopositioners that may position samples with nanometer-level precision at bandwidth of 100s of Hz and over a working envelope greater than 10x10x10 micrometers3 This thesis forms the foundation of design and fabrication knowledge required to engineer mesoscale systems to meet these needs.The design combines a planar silicon flexure bearing and unique moving-coil microactuators that employ millimeter-scale permanent magnets and stacked, planar-spiral micro-coils. The new moving-coil actuator outperforms previous coil designs as it enables orthogonal and linear force capability in two axes while minimizing parasitic forces. The system performance was modeled in the structural, thermal, electrical, and magnetic domains with analytical and finite-element techniques. A new method was created to model the three-dimensional permanent magnet fields of finite magnet arrays. The models were used to optimize the actuator coil and flexure geometry in order to achieve the desired motions, stiffness, and operating temperature, and to reduce thermal error motions.A new microfabrication process and design-for-manufacturing rules were generated to integrate multilayer actuator coils and silicon flexure bearings. The process combines electroplating for the copper coils, a silicon dioxide interlayer dielectric, and deep reactive-ion etching for the silicon flexures and alignment features.

(cont.) Microfabrication experiments were used to formulate coil geometry design rules that minimized the delamination and cracking of the materials that comprise the coil structure. Experiments were also used to measure the previously-unreported breakdown strength of the unannealed, PECVD silicon dioxide interlayer dielectric. The results of this research were used to design and fabricate a meso-scale nanopositioner system. The nanopositioner was measured to have a range of motion of 10 micrometers in the lateral directions, a range of 2 micrometers in the out-of-plane direction, an angular range of 0.5 degrees, and a first mode resonant frequency at 900 Hz. Open-loop calibration has been shown to minimize parasitic in-plane motion to less than 100 nm over the range of motion.