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）薄膜作动器对于微型机械具有许多优点，例如，薄膜具有三种功能；1)臂的框架，2)臂的关节，3)臂的致动器，所述薄膜以低驱动电压无摩擦致动臂。为了在硅衬底上研制微米尺寸的RSMA致动器系统，建立了TiNi合金薄膜的溅射沉积技术和湿法蚀刻工艺。然而，据报道，与大块钛合金相同的热处理方法无法使溅落的非晶薄膜结晶，因为薄膜从硅衬底上剥离。为了解决这一问题，本研究提出了一种利用焦耳热的电流直接穿过硅片上的TiNi合金薄膜的热处理方法。研究了直接焦耳加热和常规炉处理的TiNi薄膜的可逆形状记忆效应。结果表明，采用直接焦耳热的热处理系统对溅射沉积的TiNi薄膜的结晶是有效的。该系统不仅具有实现TiNi薄膜不剥离结晶的潜力，而且具有实现形状记忆热处理的潜力。用直接焦耳热结晶的钛膜热比用常规炉结晶的钛膜热表现出更好的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.