Nanomechanical Properties Group, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
Nanotechnology. 2012 Jun 1;23(21):215703. doi: 10.1088/0957-4484/23/21/215703. Epub 2012 May 3.
In this work, a new procedure is demonstrated to retrieve the conservative and dissipative contributions to contact resonance atomic force microscopy (CR-AFM) measurements from the contact resonance frequency and resonance amplitude. By simultaneously tracking the CR-AFM frequency and amplitude during contact AFM scanning, the contact stiffness and damping were mapped with nanoscale resolution on copper (Cu) interconnects and low-k dielectric materials. A detailed surface mechanical characterization of the two materials and their interfaces was performed in terms of elastic moduli and contact damping coefficients by considering the system dynamics and included contact mechanics. Using Cu as a reference material, the CR-AFM measurements on the patterned structures showed a significant increase in the elastic modulus of the low-k dielectric material compared with that of a blanket pristine film. Such an increase in the elastic modulus suggests an enhancement in the densification of low-k dielectric films during patterning. In addition, the subsurface response of the materials was investigated in load-dependent CR-AFM point measurements and in this way a depth dimension was added to the common CR-AFM surface characterization. With the new proposed measurement procedure and analysis, the present investigation provides new insights into characterization of surface and subsurface mechanical responses of nanoscale structures and the integrity of their interfaces.
在这项工作中，演示了一种新的方法，可从接触共振频率和共振幅度中提取接触共振原子力显微镜（CR-AFM）测量的保守和耗散贡献。通过在接触 AFM 扫描过程中同时跟踪 CR-AFM 的频率和幅度，可以在铜（Cu）互连和低 k 介电材料上以纳米级分辨率绘制接触刚度和阻尼。通过考虑系统动力学和包含的接触力学，对这两种材料及其界面进行了详细的表面力学特性研究，包括弹性模量和接触阻尼系数。使用 Cu 作为参考材料，对图案化结构的 CR-AFM 测量显示，与原始未图案化薄膜相比，低 k 介电材料的弹性模量显着增加。这种弹性模量的增加表明，在图案化过程中，低 k 介电膜的致密化得到了增强。此外，还通过负载相关的 CR-AFM 点测量研究了材料的亚表面响应，从而在常见的 CR-AFM 表面特性中添加了深度维度。通过新提出的测量程序和分析，本研究为纳米结构的表面和亚表面机械响应及其界面完整性的特性提供了新的见解。
