Yang Fuzhong, Zhang Ming, Zhu Yu, Ye Weinan, Wang Leijie, Xia Yizhou
State Key Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China.
Beijing Lab of Precision/Ultra-Precision Manufacture Equipment and Control, Tsinghua University, Beijing 100084, China.
Sensors (Basel). 2019 Jul 22;19(14):3219. doi: 10.3390/s19143219.
In the displacement measurement of the wafer stage in lithography machines, signal quality is affected by the relative angular position between the encoder head and the grating. In this study, a two-degree-of-freedom fiber-coupled heterodyne grating interferometer with large operating range of rotation is presented. Fibers without fiber couplers are utilized to receive the interference beams for high-contrast signals under the circumstances of large angular displacement and ZEMAX ray tracing software simulation and experimental validation have been carried out. Meanwhile, a reference beam generated inside the encoder head is adopted to suppress the thermal drift of the interferometer. Experimental results prove that the proposed grating interferometer could realize sub-nanometer displacement measurement stability in both in-plane and out-of-plane directions, which is 0.246 nm and 0.465 nm of 3σ value respectively within 30 s.
在光刻机晶圆台的位移测量中，信号质量受编码器头部与光栅之间的相对角位置影响。本研究提出了一种具有大旋转工作范围的两自由度光纤耦合外差光栅干涉仪。在大角度位移情况下，利用无光纤耦合器的光纤接收干涉光束以获得高对比度信号，并进行了ZEMAX光线追迹软件模拟和实验验证。同时，采用在编码器头部内部产生的参考光束来抑制干涉仪的热漂移。实验结果表明，所提出的光栅干涉仪在平面内和平面外方向均可实现亚纳米级的位移测量稳定性，在30 s内3σ值分别为0.246 nm和0.465 nm。
