After sputter-deposited amorphous TiNi films were subjected to heat treatment higher than 600 K, the shape memory alloys (SMAs) showed strong dependence of the transformation temperatures on heat treatment conditions and composition. Unlike Ni-rich films, the transformation temperatures of Ti-rich films are above the ambient temperature and largely depend on annealing temperatures from 600 to 1200 K. But they remain relatively constant on the various annealing temperature domains, 600–740 K, 740–1000 K, 1000 K +, delimited by exothermic peaks originating from the formation of precipitates. The measurements by differential scanning calorimetry, performed on TiNi thin films annealed below 740 K, showed transformation temperatures appropriate for medical applications and very small transformation temperature hysteresis of 3 K, resulting in a beneficial effect of SMA cyclic microactuators. Furthermore, using these lower annealing temperatures reduces both thermal and mechanical stresses and makes possible the development of SMA micro-actuators on substrates, that are unstable at elevated temperatures, and on electronic devices.

More and more technologies and new materials have been combined with silicon process technologies to enhance the performances of microsystems and extend the application fields. Among these technologies, the Shape Memory Alloys (SMA's) as thin films have been developed recently. They have been shown to induce high displacement and large force/mass ratio under low voltage. They can produce work output higher than can be provided with other kinds of actuators. However, such SMA actuators are not easy to make because specific annealing treatments or mechanical bias springs are needed to realize cyclic device operation. Moreover, adhesion problems of SMA thin films may occur during the annealing treatment. We have developed a simple fabrication process allowing a reliable operation principle of a micromembrane. The cyclic actuation is ensured by membrane thickness residual stresses that avoids the assembling steps. These membranes whose surface varies from 200x200 mu m(2) up to 2x2 mm(2) have been successfully tested. As developed, they are very adapted to integration process of microelectronics and can be applied to many applications such as optical, fluidic devices, and especially for biomedical. applications as SMA's are biocompatible.

The sputtering of TiNi polycrystalline alloys without and with a titanium mesh has been investigated for the development of shape memory alloy (SMA) micro-actuators. The thickness and composition distributions of TiNi thin films have been determined by Rutherford backscattering spectroscopy (RBS). The composition of sputtered films was demonstrated to depend on the density of the titanium mesh and the distance from the target center, thus enabling easy fabrication of high and low temperature SMA actuators. The transition temperatures and resistivity have been measured with respect to the composition.