Non-contact optical probe with nanometer resolution and large measurement range based on the astigmatism method

作者：Xu, Jian; Huang, Qiangxian^*; Zhao, Zhihao; Chen, Xinlei; Zhang, Liansheng; Cheng, Rongjun; Pan, Qiaosheng; Li, Ruijun

来源：MEASUREMENT, 2023, 222: 113717.

DOI：10.1016/j.measurement.2023.113717

• Non -contact probe
• Longitudinal measurement
• Range expansion
• Nanometer resolution

In the measurement field of micro/nano devices, many instruments have a contradiction between high resolution and large measurement range. This paper developed a non-contact optical nanometer probe based on the astigmatism method. This probe employs a high numerical aperture (NA) focusing lens to achieve nanometer resolution of the longitudinal measurement. Meanwhile, a longitudinal scanning measurement method based on two focus error signal (FES) curves is proposed to break the limit of low measurement range caused by high NA value. Therefore, it enables the probe to achieve the nanometer resolution of longitudinal measurement and large measurement ranges. The experiment results show that the longitudinal measurement resolution of the proposed probe is better than 1 nm, and the repeatability error is 17 nm. Combined with the high-precision microstage, the longitudinal range is greater than 15 mu m. The proposed probe can be used for large-range longitudinal noncontact measurements with nano-scale measurement requirements.