| Lithography machine is the most important equipment to realize the mass manufacture of digital chip.As the core component of lithography machine,the precision of lithography workbench track tracking control and the precision of leveling and focusing control have a direct impact on the final setting precision,which is also an important index to measure the performance of lithography machine.At present,the control methods and techniques of lithography workpiece table scanning trajectory tracking have been widely studied,but the leveling and focusing control of workpiece table in motion is relatively less studied.In this paper,the leveling and focusing platform of the multi-degree-of-freedom workbench of the lithography machine is taken as the control object for research work.Advanced system modeling,control theory and methods are used to solve the coupling and interference suppression problems which cannot be solved under the traditional control methods,so as to improve the leveling and focusing precision of the system.The main research contents are as follows:1)The working principle of the system is studied.On this basis,the tracking control experiment and interference measurement experiment of the leveling and focusing platform are carried out by using the classical control scheme.The sinusoidal excitation was carried out on multiple axes of the system,the dynamic response characteristics were analyzed,and the coupling of multi-input multi-output system and the influence of interference characteristics on the system were determined.2)To solve the coupling problem of MIMO system,firstly,in order to quantitatively analyze the final leveling and focusing effect,the motion control logic transformation and precision index decomposition of the system were carried out.Then,based on the coupling mechanism of each degree of freedom,the force and displacement transformation relationship between the driving motor and the center of mass of the leveling focusing platform and the center of exposure point was deduced.The dynamic coupling model among the three motors was established,and the decoupling control algorithm of the leveling focusing platform was designed based on the inverse dynamic model.Finally,the parameters of the decoupled subsystem were identified,and the corresponding trajectory tracking experiment was designed to verify the decoupling effect and the independence of the control channel.3)In order to improve the tracking and positioning accuracy of the system,an adaptive sliding mode control algorithm based on nonlinear disturbance observer is proposed.This algorithm combines the nonlinear disturbance observer with the adaptive inversion sliding mode controller to compensate the disturbance of the system to the maximum extent,and improve the robustness of the system and the performance of trajectory tracking and location.And the corresponding tracking control experiment is carried out.The experimental results show that compared with the average tracking error of the traditional adaptive sliding mode control algorithm 3.8 ?m,the average tracking error of the control algorithm designed in this paper drops to 0.08 ?m.The maximum tracking error is also reduced from 21.4 ?m to 4.2 ?m,which obviously improves the tracking and positioning accuracy of the system.Finally,the control method studied in this paper is applied to the control experiment of the leveling and focusing stage of the six-degree-of-freedom precision workpiece table of the domestic lithography machine.The results show that,compared with the traditional leveling and focusing control scheme of the workpiece table,the control scheme designed in this paper can meet the requirement of repeated positioning accuracy of 110 nm.In other words,it can achieve higher tracking accuracy and stronger interference suppression ability,and achieve higher leveling and focusing accuracy. |
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