亚微米厚铜薄膜的微观结构及疲劳损伤行为

MICROSTRUCTURES AND FATIGUE DAMAGE OF SUBMICRON THICK COPPER FILMS

在具有高弹性和力学稳定性的柔性基底上,用磁控溅射系统制备了亚微米厚铜薄膜,利用透射电镜(TEM)、扫描电镜 (SEM)电子背散射成像及 X 射线衍射(XRD)对铜薄膜进行了微观结构表征．采用恒载荷幅控制研究了亚微米厚度铜薄膜的疲劳损伤行为．结果表明：退火后的铜薄膜呈现强烈的(111)织构,薄膜中存在大量的微米、纳米尺度孪晶．在恒载荷幅作用下,亚微米厚的薄膜不易产生疲劳挤出和微裂纹,疲劳裂纹容易在界面处萌生,孪晶附近的位错塞积及界面附近变形的不协调性导致了疲劳裂纹的产生．而亚微米厚铜薄膜疲劳强度的提高来源于薄膜厚度、晶粒尺寸和孪晶尺寸三个微尺度的约束．

Submicrons thick Cu films were deposited on polyimide substrates with high elasticity and mechanical stability by a magnetron sputtering system. Microstructures of the Cu films were characterized by TEM, electron backscatter imaging of SEM as well as XRD technique. Fatigue damage behaviors of the submicron thick Cu films were investigated under constant load amplitude control. It was found that there exists a large number of micro/nanoscale twins in the annealed films and （111） texture formed in the films. Fatigue extrusions and cracking in the Cu films were suppressed under constant load amplitude control. The fatigue cracks dominantly initiate at the interfaces, where exist strong dislocation interaction at twin boundaries and deformation incompatibility near the interfaces. The enhance of fatigue strength of the submicron thick Cu films results from the constraints of three scales of film thickness, grain size and twin size.