改进型微悬臂梁弹性常数标定系统

摘要

Microcantilever is the key component of force sensor in AFM. The prerequisite for the accurate quantification of the micro-force is the traceable and accurate measurement of the normal and lateral spring constant of the microcanti-lever. Due to the limitation of microelectronics processing technology,the dimension parameters and the normal spring constant of the microcantilever cannot be accurately calibrated. Meanwhile the lateral spring constant is lack of widely ac-cepted calibration methods. The calibration system was improved based on the balance method. The combination of the ultra-precision electromagnetic balance and the optical lever structure fulfills the accurate measurement of the bending displacement and the force of the microcantilever and improves the accuracy of the normal spring constant. Microplate samples and inclined loading methods were designed to realize the indirect measurement of the lateral spring constant. Three commercial microcantilevers were calibrated respectively,and the dimension parameter method based on SEM was used as a comparison. The experimental results have good repeatability and small relative deviations. It indicates that the calibration system and method could be used as a reference for the calibration of the spring constants of microcantilevers.%微悬臂梁作为原子力显微镜中感受微观力的关键元件,其法向和横向弹性常数的可溯源测量是微观力准确定量的前提.受微电子加工工艺的限制,微悬臂梁形状参数与其法向弹性常数无法准确标定,其横向弹性常数更是缺少广泛认可的标定方法.在天平法的基础上对标定系统进行了改进设计,超精密电磁天平与光杠杆结构的结合,能够准确测量微悬臂梁弯曲量及所受作用力,提高了法向弹性常数的准确度.设计了微孔样片和倾斜加载方式,实现了横向弹性常数的间接测量.基于本系统分别对3种商用微悬臂梁的法向或横向弹性常数进行了标定,并采用基于扫描电镜的尺寸参数法比对测量,实验结果重复性好、相对偏差小.研究结果表明该校准系统和方法可作为微悬臂梁弹性常数标定的参考方法.