Low Temperature Heat Process of Reversible Shape Memory Alloy Thin Film on Si Water

可逆形状记忆合金（RSMA）（TiNi合金）薄膜驱动器在微机械中具有许多优点，例如，薄膜具有三种功能：1）臂的框架，2）臂的关节和3）臂的致动器，并且薄膜可以在低驱动电压下无摩擦地致动臂。为研制硅基微米级RSMA驱动器系统，建立了溅射沉积TiNi合金薄膜和湿法腐蚀工艺。然而，据报道，与用于块状TiNi合金的方法相同的热处理不能成功地使溅射的非晶薄膜结晶，因为薄膜从硅衬底剥离。本研究针对此问题，提出一种利用电流焦耳热直接通过矽晶圆上之TiNi合金薄膜进行热处理的方法。研究了直接焦耳热处理和常规热处理对TiNi薄膜可逆形状记忆效应的影响.结果表明，直接焦耳热热处理系统对溅射沉积的TiNi薄膜的晶化是有效的.该系统不仅有可能实现TiNi薄膜的不剥离晶化，而且有可能实现形状记忆热处理.用焦耳热直接晶化的TiNi薄膜比用常规炉晶化的TiNi薄膜具有更好的RSME。

Reversible shape Memory alloy (RSMA) (TiNi alloy) Thin Film actuators have many advantages for micromachines, for example, the films have three functions ; 1) a frame of the arm, 2) a joint of the arm and 3) an actuator of the arm and the films could actuate the arm without frictions with low driving electrical voltage. To develop the micron sized actuator system with RSMA on silicon substrates, the spattering deposition technique for the thin films of TiNi alloy and the wet etching process were established. However, the same heat treatment as the method for bulk TiNi alloy was reported to be unsuccessful to crystallize the spattered amorphous thin films because the thin films were stripped off from the silicon substrates. In this study, to solve the problem, a heat treatment method by Joule's heat of electrical current direct through the TiNi alloy thin films on the silicon wafers was proposed. Reversible shape memory effect of TiNi thin films treated by direct Joule's heat and the conventional furnace was evaluated.The results indicate that the heat treatment system using direct Joule's heat is effective for the crystallization of the sputtering deposited TiNi thin films.This system has potential to realize not only the crystallization of TiNi thin films without stripping from silicon wafer but also shape memorizing heat treatment. TiNi film heat crystallyzed by the direct Joule's heat show better RSME than that by the conventional furnace.