基于SEM-SPM原位纳米压痕超薄铜薄膜弹性模量研究

本文利用自主研发的扫描电子显微镜-扫描探针显微镜联合测试系统(SEM-SPM),研究了直流磁控溅射(DCMS)和原子层沉积(ALD)两种成膜方式对40、60和80 nm超薄铜薄膜弹性模量的影响.基于赫兹理论和King模型的计算结果表明,利用DCMS得到不同厚度铜薄膜的弹性模量值在(95±2)Gpa~(125±4)GPa之间,而通过ALD得到的铜薄膜弹性模量值在(99±2)Gpa~(154±6)GPa之间.对比分析可知,不同厚度的铜薄膜弹性模量比块体铜材料的弹性模量(90 GPa)大6%~71%,且通过两种不同方式沉积得到的铜薄膜弹性模量值都随着薄膜厚度的增加而减小,表现出明显的尺寸效应.而且对于同一厚度的铜薄膜,利用ALD沉积的弹性模量比DCMS的大4.2%~23.2%,由透射电子显微图像对比分析可知,前者的平均晶粒尺寸是后者的60%,纳米晶粒小尺寸效应可能是薄膜弹性模量增大的原因.

Study on elastic modulus of ultra-thin copper films by in-situ SEM-SPM nanoindentation

In this paper, based on the Hertzian contact theory and King model, the elastic modulus of ultra-thin copper film with thickness of 40, 60, 80 nm deposited by direct current magnetron sputtering ( DCMS) and atomic deposition ( ALD) in the Si of (100) direction were investigated by scanning electron microscopy-scanning probe microscopy ( SEM-SPM) combined system. It has been found that the elastic modulus of Cu films with various thicknesses deposited by DCMS and ALD were obtained as from (95 ± 2) GPa to (125 ± 4)GPa and from (99 ± 2)GPa to (154 ± 6)GPa, and they are 6% ~71% larger than that of their bulk counterpart (90 GPa) . Furthermore, the elastic modulus of Cu films, either deposited by DCMS or by ALD, are closely related to the film thickness and decreases linearly with the increase of film thickness. In the case of same thickness, elastic modulus of the films obtained by ALD show 4. 2% ~23. 2% higher than those obtained by DCMS because of smaller grain size.