Design of ultra precision fixtures for nano-manufacturing

Abstract

This thesis presents the design, modeling, fabrication and experimental validation of an active precision fixturing system called the Hybrid Positioning Fixture (HPF). The HPF uses the principles of exact constraint, combined with principles and means of Nanomanipulation to fixture components with tens of nanometer accuracy and repeatability. Achieving this level of performance requires addressing three fundamental limitations of precision fixtures; (1) Elimination of stiction via integrated compliance, (2) Integration of sensors and actuators to enable correction of systematic and time variable alignment errors, and (3) Improvement of fixture contacts' stability and longevity via hard coatings. Conceptual and analytic models are developed for the integration of compliant elements, sensors and actuators within the fixture. The validity of these concepts/models is tested via a prototype HPF. Analytic models and design rules are provided to guide designers in the use of thin coatings for precision fixture contacts. These are based upon non-linear finite element analysis. The effects of hard and soft interlayer, which reduce coating stresses and improve coating adherence, are also analyzed. The performance of the HPF is measured in two modes, passive (constant voltage supplied to piezoelectric actuators) and active (actuators supplied with different input voltages). The HPF is shown to be capable of 3 [sigma], passive repeatability of 100nm in x, y, and repeatability of 2 [mu] radian in [theta]x, [theta]y and [theta]z. Active tests indicate that the HPF is capable of accuracy of better than 5nm.

(cont.) The fixture is shown to have a load capacity of 450 N and stiffness of 7N/[mu]m. The combination of nanometer-level accuracy, repeatability and high load capacity make the HPF suitable for a range of current and emerging applications such as photonics packaging, mask to wafer alignment, nanomanufacturing, nano-scale research experiments and automated transfer lines.