TiNi (shape memory) films silicon for MEMS applications

Author

Wolf, Richard H. ; Heuer, Arthur H.

Author_Institution

Dept. of Mater. Sci. & Eng., Case Western Reserve Univ., Cleveland, OH, USA

Volume

4

Issue

4

fYear

1995

fDate

12/1/1995 12:00:00 AM

Firstpage

206

Lastpage

212

Abstract

TiNi shape memory alloy in thin film form is an excellent candidate for MEMS microactuation. Using RF sputter deposition, thin films of TiNi (51.7 at% Ti-48.3 at% Ni) have been formed on silicon substrates and produced shape memory behavior at approximately 60°C. Films were amorphous when deposited and were subsequently annealed at 515°C for 30 min. to crystallize the shape memory microstructure. Excellent adherence was achieved onto silicon, SiO₂ and poly-silicon surfaces. Microfabrication was used to create TiNi diaphragms, which exhibited useful shape memory microactuation and other desirable mechanical properties. The diaphragms recovered greater than 2% strain when heated through the phase transformation temperature, providing a maximum work density of at least 5×10⁶ J/m ³. This work density is higher than that of any other type of microactuation

Keywords

diaphragms; elemental semiconductors; microactuators; nickel alloys; shape memory effects; silicon; sputter deposition; titanium alloys; 30 min; 515 degC; 60 degC; MEMS microactuation; RF sputter deposition; Si; TiNi-Si; adherence; diaphragms; mechanical properties; microfabrication; phase transformation temperature; shape memory alloy; work density; Amorphous materials; Annealing; Micromechanical devices; Radio frequency; Semiconductor films; Semiconductor thin films; Shape memory alloys; Silicon; Sputtering; Substrates;

fLanguage

English

Journal_Title

Microelectromechanical Systems, Journal of

Publisher

ieee

ISSN

1057-7157

Type

jour

DOI

10.1109/84.475547

Filename

475547