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

Volume

11

Issue

1

fYear

2002

fDate

2/1/2002 12:00:00 AM

Firstpage

68

Lastpage

77

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;

fLanguage

English

Journal_Title

Microelectromechanical Systems, Journal of

Publisher

ieee

ISSN

1057-7157

Type

jour

DOI

10.1109/84.982865

Filename

982865