TiNi (shape memory) films on silicon for MEMS applications

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 degrees C. Films were amorphous when deposited and mere subsequently annealed at 515 degrees 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 x 10(6) J/m(3). This work density is higher than that of any other type of microactuation. [131]