Design Of 3-DOF Magnetic Levitation Attitude Adjustment Mechanism

Immersion lithography machines have significantly improved the lithography resolution,and at the same time have minimal changes to traditional lithography machines,so they have become mainstream equipment in the manufacture of integrated circuits at 65 nm and below.The immersion unit is a key component in the immersion lithography machine.In the scenarios of immersion unit installation,commissioning,and work,there is a need to adjust its three degrees of freedom poses of z,Rx and Ry.The three-degree-offreedom pose adjustment of the immersion unit z,Rx and Ry is performed by a pose adjustment mechanism.The purpose of this paper is to design a pose adjustment mechanism that satisfies the travel and positioning accuracy requirements of the three degrees of freedom z,Rx and Ry in the motion control index of the immersion unit.Through the design and analysis of the overall structure of the system,the work is mainly divided into three parts: one is the structural design of the posture adjustment mechanism,the other is the motion analysis of the posture adjustment mechanism,and the third is to make a prototype of pose adjustment mechanism and design control algorithm for performance verification.Firstly,the structure of the mechanism is designed.The structure design includes magnetic suspension gravity compensator design,cantilever design and voice coil motor selection.The function of maglev gravity compensator is to compensate the gravity of mechanism.Its design is based on the layout of Halbach permanent magnet array.The cantilever beam is designed to increase its horizontal bending stiffness,so that it can effectively limit the horizontal freedom of immersion element.Voice coil motor is the actuator of position and attitude adjustment mechanism.The thrust index of voice coil motor is calculated and the appropriate voice coil motor is selected.Secondly,kinematic derivation,simulation verification and kinematic characteristics analysis of the mechanism are carried out.According to the zyx Euler transform,the forward and inverse kinematics solutions of the mechanism are deduced,and the joint simulation of Adams and Simulink is carried out to verify the kinematics derivation.The analysis of motion characteristics includes theoretical error analysis,singularity analysis,adjoint motion analysis and three degrees of freedom theoretical value range analysis,which describes the motion characteristics of the pose adjustment mechanism in a comprehensive way in theory.Finally,the experimental prototype of the pose adjustment mechanism is made,the control algorithm is designed and the performance is verified.First,the electrical system of the mechanism and the three circles debugging of voice coil motor are built.Then,the feedforward control algorithm based on error is demonstrated and designed to measure the error of three degrees of freedom and summarize the error equation.Finally,using the feedforward control algorithm based on the error to verify the travel and accuracy performance of the mechanism.The experimental results show that the immersion unit can meet the travel and accuracy requirements under the error feedforward control.To sum up,the designed mechanism can meet the requirements of stroke with z of 1.8mm,stroke with Rx and Ry of ± 1.3mrad,and accuracy with z of ± 5?m,and stroke with Rx and Ry of ± 0.1mrad.