确定微纳米尺度金属薄膜拉伸分叉点的实验研究

Experimental Investigation on Determining the Bifurcation of Micro-Nano Scale Metallic Thin Film Subjected to Tensile Loading

为了确定微纳米尺度金属薄膜的拉伸分叉点,本文使用磁控溅射镀膜技术,在PI(聚酰亚胺)基底上沉积500nm厚的铜薄膜,制作薄膜/基底结构拉伸试件。在单轴拉伸作用下,通过测量拉伸加载过程中铜薄膜的电阻变化情况,得到薄膜电阻随应变变化的关系,并与理论推导的结果进行对比分析,从而确定了塑性阶段理论曲线与实验曲线分离的点,即铜薄膜的分叉点。以此为基础,研究了铜薄膜在单轴拉伸作用下的分叉行为。研究结果表明,沉积于PI基底上的微纳米尺度铜薄膜在单轴拉伸下,经过弹性变形阶段后,很快就发生分叉,然后产生破坏,而塑性变形阶段和局部化阶段较短;弹性阶段薄膜的电阻变化速率很小,塑性阶段薄膜的电阻变化速率稍有增大,而当薄膜表面开始出现微裂纹后,电阻变化速率急剧增大。

In order to determine the bifurcation of micro-nano scale metallic thin film subjected to uniaxial tensile loading, using magnetron sputtering technology, copper film with 500nm thickness was deposited on a PI（polyimide） substrate to manufacture stretching specimens with film/substrate structure. Under uniaxial tensile loading, the relation between film resistance and film strain can be obtained through measuring the resistance variation of copper film during tensile loading. Experimental data were compared with theoretical result. Thus, it is determined that the separation point between theoretical curve and experimental curve on plastic stage is exactly the bifurcation point of copper film. Based on above argument, the bifurcation behavior of copper thin film subjected to uniaxial tensile loading was studied. Results show that the bifurcation of micro-nano scale copper film deposited on PI substrate and subjected to uniaxial tensile loading occures soon after elastic deformation stage, which causes film damage and shorter plastic deformation stage and localized stage. There is very small increasing rate of resistance on elastic stage and slightly larger increasing rate of resistance on plastic stage; when micro crack occures on film surface, resistance increasing rate rapidly increases.