Abstract
This paper presents the design and realization of a three degrees of freedom (DOFs) displacement measurement system composed of Hall sensors, which is built for the XYθz displacement measurement of the short stroke stage of the reticle stage of lithography. The measurement system consists of three pairs of permanent magnets mounted on the same plane on the short stroke stage along the Y, Y, X directions, and three single axis Hall sensors correspondingly mounted on the frame of the reticle stage. The emphasis is placed on the decoupling and magnetic field fitting of the three DOFs measurement system. The model of the measurement system is illustrated, and the XY positions and θZ rotation of the short stroke stage can be obtained by decoupling the sensor outputs. A magnetic field fitting by an elliptic function-based compensation method is proposed. The practical field intensity of a permanent magnet at a certain plane height can be substituted for the output voltage of a Hall sensors, which can be expressed by the elliptic function through experimental data as the crucial issue to calculate the three DOFs displacement. Experimental results of the Hall sensor displacement measurement system are presented to validate the proposed three DOFs measurement system.
Highlights
Precision metrology plays an important role in on-machine measurement, positioning and manufacturing, such as machine tools, coordinate measuring machines and semiconductor manufacturing [1].the accuracy of these machines is significantly determined by the translational and rotational stages, so multi-DOF precision measurement of the stages is crucial
Three pairs of permanent magnets used for XYθZ displacements measurement are fixed on the SS stage along the X and Y directions, and the three corresponding Hall sensors are mounted on the SS frame above the permanent magnets along the direction of the equipotential line, so the movement of the SS stage relative to the SS frame perpendicular to the equipotential line in the XOY plane can be measured on the premise that the SS stage is held to the expected height by the three gravity compensators (GCs), which is crucial for the relative motion control between the LS motion and SS motion
A three degrees of freedom displacement measurement system composed of three Hall sensors is presented
Summary
Precision metrology plays an important role in on-machine measurement, positioning and manufacturing, such as machine tools, coordinate measuring machines and semiconductor manufacturing [1]. The Stewart parallel structure was applied in multi-DOF measurement as a MEMS sensor by Mura [4], and a sensitivity analysis of the configuration was carried on concerning geometrical characteristic and displacement amplitude [5]. Allred developed another Gough-Stewart platform-based measurement solution which integrates linear displacement sensors into a high capacity laminate bearing [6]. A magnetic field fitting method by an elliptic function is proposed to analytically express the magnet field line at a certain height, by which the practical field intensity of a permanent magnet can be substituted for the output voltage of the Hall sensors to solve the position of the stage. The decoupling and magnetic field fitting method is validated by experiments
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