Title :
Three-dimensional thin-film shape memory alloy microactuator with two-way effect
Author :
Gill, John J. ; Ho, Ken ; Carman, Greg P.
Author_Institution :
Dept. of Mech. Aerosp. Eng., California Univ., Los Angeles, CA, USA
fDate :
2/1/2002 12:00:00 AM
Abstract :
A novel thin film (micrometer thickness) shape memory alloy (SMA) micro actuator is presented in this paper. The thin film SMA with composition of approximately 50:50 nickel titanium (NiTi) is sputter-deposited onto a silicon wafer in an ultra high vacuum system. Transformation temperatures of the NiTi film are determined by measuring the residual stress as a function of temperature. The transformation temperature is independent of the presence of chromium (Cr) used as an adhesion layer, or being exposed to air before annealing. A mixture of hydrofluoric acid (HF), nitric acid (HNO3) and deionized (DI) water is used to etch the film. Different etch masks are evaluated to protect the NiTi film during the etching. Among the masks tested, a thick photoresist (AZ-4620) produces the best result. The NiTi membrane is hot-shaped into a three-dimensional (3-D) dome shape using a stainless-steel jig. Results indicate the membrane exhibits two-way effect. The performance of the SMA micro actuator is characterized with a laser measurement system for deflection versus input power and frequency response
Keywords :
adhesion; frequency response; internal stresses; measurement by laser beam; microactuators; nickel alloys; photoresists; shape memory effects; titanium alloys; NiTi-Si; adhesion layer; etch masks; frequency response; input power; laser measurement system; photoresist; residual stress; shape memory alloy microactuator; stainless-steel jig; transformation temperatures; two-way effect; ultra high vacuum system; Biomembranes; Chromium; Etching; Microactuators; Nickel; Semiconductor thin films; Shape memory alloys; Sputtering; Temperature; Transistors;
Journal_Title :
Microelectromechanical Systems, Journal of
