基体对应力诱导的纳米晶W膜开裂行为的影响

Effect of substrate constraint on stress-induced cracking of sputtered tungsten thin film

采用磁控溅射方法同时在Si(100)和聚酰亚胺(PI)基体上沉积W膜,对比研究不同基体约束对纳米晶W膜微观结构及应力诱导的开裂行为的影响.结果发现,在两种基体上W膜的裂纹形态明显不同.在Si基体上W膜的裂纹呈楔形,而在PI基体上W膜的裂纹呈半圆柱形凸起于薄膜表面.这种裂纹形态的差异源于两种基体上W膜的变形机理不同.在刚性Si基体上,W膜的裂纹扩展是通过晶粒平面内的转动实现的,而在柔性PI基体上W膜裂纹扩展是通过排列晶粒在平面内、外的转动协调完成的.分析表明,两种截然不同的开裂行为与不同基体上薄膜内应力的变化规律、基体对薄膜的异质约束能力密切相关.

A comparative investigation was performed on the stress-induced surface cracking of tungsten films sputter deposited on polyimide（PI） and Si substrates.Microscopic observations suggest that with the same film thickness,two different types of cracking behaviors were observed.Wedge-shaped cracks are formed on the surface of film deposited on the Si substrate.However,the cracks of film deposited on the polyimide consist of aligned grains.The localized plastic deformation in the nanocrystalline W film on polyimide is mediated by the alignment of grains,which results from the grain rotation along the in-plane and out-of-plane directions.However,on the Si substrates the wedge-shaped cracks originate from the in-plane rotation of grains.The analysis implies that the different deformation behaviors are associated with the evolution of stress in the film and the substrate constraint.