基于磁驱动正交悬臂探针的三维原子力显微镜技术开发

The Development of 3D Atomic Force Microscopy with Magnetically Driven-Orthogonal Cantilever Probes

本文介绍了一种基于磁驱动正交悬臂探针(magnetically driven-orthogonal cantilever probes,MDOCP)的三维原子力显微镜(three-dimensional atomic force microscopy,3D-AFM)表征方法,该方法采用两个独立的三自由度纳米扫描器,能够实现探针沿可控矢量角度跟踪扫描样品表面。该3D-AFM系统还配备了高精度旋转台,可实现360°全向成像。定制的MD-OCP包含水平悬臂、垂直悬臂和磁球三部分,其中磁球可在磁场中机械驱动OCP实现激振。垂直悬臂具有一个突出的尖端,可检测深槽和具有悬垂/凹边特征的结构。首先,对MD-OCP的设计、模拟、制造和性能分析进行了描述;其次,详细介绍了探针振幅补偿和360°旋转原点定位的方法。通过使用标准AFM阶梯光栅进行对比实验,验证了所提出方法对于陡峭侧壁和拐角处细节的表征能力,其中采用了三维地形重建方法将图像整合。通过对具有微梳结构的微机电系统(MEMS)器件进行3D表征,进一步证实了所提出基于MD-OCP的3D-AFM技术的有效性。最后,该技术被用于确定微阵列芯片的关键尺寸(critical dimensions,CD)。实验结果表明,所提出的方法可以高精度地获取三维结构的CD信息,相比于难以获得侧壁信息的二维技术,在三维微纳制造检测领域具有更好的潜力。

This paper presents a three-dimensional(3D)-atomic force microscopy(AFM)method based on magnetically driven(MD)-orthogonal cantilever probes(OCPs),in which two independent scanners with three degrees of freedom are used to achieve the vector tracking of a sample surface with a controllable angle.A rotating stage is integrated into the compact AFM system,which helps to achieve 360omnidirectional imaging.The specially designed MD-OCP includes a horizontal cantilever,a vertical cantilever,and a magnetic bead that can be used for the mechanical drive in a magnetic field.The vertical cantilever,which has a protruding tip,can detect deep grooves and undercut structures.The design,simulation,fabrication,and performance analysis of the MD-OCP are described first.Then,the amplitude compensation and home positioning for 360rotation are introduced.A comparative experiment using an AFM step grating verifies the ability of the proposed method to characterize steep sidewalls and corner details,with a 3D topography reconstruction method being used to integrate the images.The effectiveness of the proposed 3D-AFM based on the MD-OCP is further confirmed by the 3D characterization of a microelectromechanical system(MEMS)device with microcomb structures.Finally,this technique is applied to determine the critical dimensions(CDs)of a microarray chip.The experimental results regarding the CD parameters show that,in comparison with 2D technology,from which it is difficult to obtain sidewall information,the proposed method can obtain CD information for 3D structures with high precision and thus has excellent potential for 3D micro–nano manufacturing inspection.