计量型扫描电子显微镜成像的微纳米级振动

Micro-nanometer scale vibration in imaging of metrological scanning electron microscope

为提高计量型扫描电镜位移系统的稳定性及测量精度,对位移系统中的机械位移台进行仿真分析,获取相关振动参数。依据机械位移台工况建立模型,运用有限元方法对它进行静力及模态分析,获取机械位移台系统结构的振动参数;在模态分析的基础上对机械位移台进行谐响应分析,获取外界载荷频率与位移台上平面应力、应变、变形以及加速度之间的关系。机械位移台的静刚度为6.634×10~5 N/mm;水平X,Z两运动方向的耦合比分别为15.22%和17.63%;通过上层平面振动参数关于频率的响应曲线,得出危险频率为7 750Hz左右,即第8阶固有模态下的频率。X,Z两运动方向耦合较为明显,在对机械位移台进一步改进中,避开危险频率的同时,需对其进行位移补偿。

To improve the stability and measurement accuracy of the positioning system of a metrological scanning electron microscope, the mechanical displacement platform in the positioning system was simulated and analyzed, and vibration parameter values were obtained. A model of the mechanical displacement platform was established according to its working conditions, and the structural vibration parameter values of the platform were acquired by conducting static and modal analysis using the finite element method. Through the modal analysis, the harmonic response of the mechanical displacement platform was analyzed, and the relationships between the external load frequency and stress, strain, deformation, and the acceleration of the upper plane of the platform were obtained. The static stiffness of the mechanical displacement platform is 6.634×10^5 N/mm, and the coupling ratios of the horizontal X and Z movements are 15.22% and 17.63%, respectively. According to the response curve of the upper plane vibration parameter to the frequency, the dangerous frequency is approximately 7 750 Hz (i.e., the frequency under the eighth natural mode). In addition, a strong coupling is observed between the X and Z movements. For a modified design of the platform, displacement compensation should be conducted while ensuring the platform is prevented from reaching the dangerous frequency.