Positioning Apparatus Spring Force Cancellation
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Solution Overview
Problem
The positioning accuracy of coarse moving stages in exposure apparatuses is significantly affected by external disturbances from wirings and pipes, leading to errors that are about 10 times those of fine moving stages, causing variations in the relative position between the repulsion stator and mover, which in turn affect the control of the fine moving stage.
Innovation Solution
A positioning apparatus with a supporting mechanism having a spring characteristic, an actuator, and a controller that reduces position errors and cancels forces due to the spring characteristic, using a feedback control system and feedforward control to stabilize the fine moving stage's position by measuring and compensating for variations in the relative position between the stage and the base.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a coarse moving stage mechanism is used to achieve large stroke and high acceleration, then productivity is improved, but positioning accuracy deteriorates due to external disturbances from wirings and pipes
Solution Approach 1:
A supporting unit with repulsion movers and repulsion stators is introduced as an intermediary between the coarse moving stage and the fine moving stage. This intermediary actively compensates for positioning errors of the coarse stage through feedback control, thereby maintaining high positioning accuracy while allowing the coarse stage to provide large stroke and high acceleration for improved productivity.
Solution Approach 2:
The patent implements a feedback control system that continuously monitors the positioning error of the coarse moving stage and uses this information to adjust the repulsion movers, thereby correcting positioning deviations in real-time and maintaining high accuracy despite the coarse stage's susceptibility to external disturbances.
2Length of moving object
If the coarse moving stage is made larger to increase stroke, then productivity is improved, but the bandwidth of the feedback control system decreases
Solution Approach 1:
The positioning system is segmented into two independent but coordinated parts: a coarse moving stage for large-stroke movements and a fine moving stage for high-precision positioning. The supporting unit with repulsion movers bridges these segments, allowing each to operate optimally within its own bandwidth range while contributing to overall system performance.
3Adaptability or versatility
If wirings and pipes are mounted on the fine moving stage, then functionality is improved, but positioning accuracy deteriorates due to disturbances on the coarse moving stage
Solution Approach 1:
The supporting unit acts as an intermediary that isolates the fine moving stage from disturbances caused by wirings and pipes on the coarse stage. Through active feedback control, it compensates for positioning errors introduced by these disturbances, maintaining high accuracy while allowing full functionality with wirings and pipes mounted on the fine stage.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution significantly reduces position errors and improves the positioning accuracy of the fine moving stage, allowing for high-speed and precise movement, thereby enhancing the overall productivity in semiconductor device manufacturing.
Implementation Method 1
a supporting mechanism which is arranged between the stage and the base and supports the stage with a supporting portion having a spring characteristic
Implementation Method 2
an actuator which is arranged between the stage and the base so as to drive the stage
Implementation Method 3
a controller which controls the actuator, wherein the controller controls the actuator so as to reduce a position error of the stage relative to a target position
Implementation Method 4
cancel at least part of a force acting on the stage due to the spring characteristic of the supporting portion, based on the position error of the stage and a variation of a relative position between the stage and the base
Data Source
AI summary
A positioning apparatus includes a stage, a base, a supporting mechanism which is arranged between the stage and the base and supports the stage with a supporting portion having a spring characteristic, an actuator which is arranged between the stage and the base so as to drive the stage, and a controller which controls the actuator so as to reduce a position error of the stage relative to a target position and cancel at least part of a force acting on the stage due to the spring characteristic of the supporting portion, based on the position error of the stage and a variation of a relative position between the stage and the base.