A high-yield drying process for surface-micromachined structures using magnetostatic forces

Etching of sacrificial material is widely used in surface micromachining technology to form integrated micromechanical structures. The process typically consists of three steps: the removal of sacrificial-layer material using liquid chemicals, rinsing, and removal of the rinse liquid (drying). The last step is known to cause surface sticking and drastic reduction of device yield. This paper presents the latest results on the development of a novel drying technique in which surface microstructures are lifted away from the substrate plane during the liquid-removal process to avoid contact and sticking with the substrate. Electroplated Permalloy material is employed to provide torque to the microstructure through interaction with an external magnetic field. This method is especially useful for microdevices with large surface areas. Test structures with contact-surface areas larger than 1 × 1 mm² are fabricated to demonstrate the high yield (100%) achievable using this technique.