Six Degrees Of Freedom Micro Displacement Measurement System Based On Hall Sensors For Short Stroke Stage

Short stroke stage is the core component of the wafer stage of lithography system.Before performing lithography,the chuck of the short stroke stage should be adjusted within the measuring range of the laser interferometer to find the system zero position of the lithography system.The relative movement positions of chuck and short stroke stage are measured by 6-DOF Hall sensor system in the adjustment processing.During the macro and micro joint debugging of the wafer stage,the Hall sensor system should be maintain in the measurement and communication status.Once the movement of the short stroke stage exceeds the measurement range of the laser interferometer,the system immediately switches to the closed-loop control of the Hall sensor to ensure the controllability of the macro-micro system.This paper takes the short stroke stage of wafer stage as the research object.Based on the existing structure of the short stroke stage,a Hall measurement model with 6-DOF is designed to measure the position of center-of-mass of the short stroke stage.The completed work is as follows:Firstly,a 6-DOF Hall measurement model was established to obtain the displacement matrix of the Hall sensor's measurement direction displacement and the center-of-mass position of the chuck.Based on the laser sensor measurement signal,combined with the Hall sensor voltage signal,the least squares fitting method was used.The method solves the relationship matrix of the Hall sensor measurement direction displacement and the Hall voltage,and realizing the decoupling of the Hall output voltage and the 6-DOF position of the center-of-mass position of the chuck.Secondly,the signal acquisition board of six-channel Hall sensor is designed,and the 6-channel 16-bit A/D conversion chip is used to achieve 6-channel Hall voltage synchronization acquisition.After receiving 5k clock signal of the control system,6.25 Mbps baud rate communication with control system is achieved.Finally,a single-DOF experiment platform and a 6-DOF measurement system were established,the individual Hall sensors and signal acquisition board functions and the decoupling method of the 6-DOF measurement system were verified respectively.The experiment data of single-channel Hall sensor shows that the single Hall sensor has a resolution of 1?m in a 4mm range,with the nonlinearity of 1.23%,and the system can be stabilized within 3 minutes.The experiment results of 6-DOF measurement system show that the six-channel Hall measurement system can be used to decouple the center-of-mass position of the chuck,and the decoupling results of the Hall measurement system are evaluated based on the laser sensor measurement system.The results show that the linear displacement error is 120 ?m and the angular displacement error is 0.034°.