Interferometer Switching Correction for Stage Acceleration Errors
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Solution Overview
Problem
Existing positioning apparatuses experience measurement errors due to stage acceleration/deceleration, particularly in semiconductor exposure systems, where interferometer switching during these phases leads to positional inaccuracies due to mirror deformation, affecting the dynamic characteristics and accuracy of stage control.
Innovation Solution
A positioning apparatus that includes a measurement system and a correction unit, which measures the stage position and corrects for acceleration-induced errors by switching between interferometers based on pre-calculated correction coefficients derived from the relationship between acceleration and mirror deformation, ensuring accurate positioning across the entire stroke.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If interferometers are switched during stage acceleration/deceleration to maintain measurement coverage, then measurement continuity is improved, but measurement precision deteriorates due to mirror deformation
Solution Approach 1:
The patent applies preliminary action by calculating correction values in advance based on the relationship between stage acceleration and mirror deformation. Correction tables are pre-computed for different acceleration conditions, allowing the system to compensate for deformation effects before they occur during interferometer switching, thus maintaining both measurement continuity and precision
Solution Approach 2:
The patent changes the measurement parameter by introducing correction values that account for mirror deformation under different acceleration conditions. The system dynamically adjusts the measurement readings based on the stage's acceleration state, transforming the raw measurement data into corrected position information that compensates for the physical deformation of measurement components
2Length of moving object
If multiple interferometers are used to cover the entire stage stroke, then measurement coverage is improved, but device complexity increases
Solution Approach 1:
The patent introduces correction values as an intermediary element that mediates between the multiple interferometers and the final position measurement. This correction mechanism acts as a bridge that harmonizes the measurements from different interferometers, compensating for their individual limitations and enabling extended stroke coverage without proportionally increasing system complexity
Solution Approach 2:
The patent segments the measurement system into multiple interferometers that cover different portions of the stage stroke. Each interferometer handles a specific segment of the total travel distance, and the system switches between segments as needed, allowing the overall measurement range to exceed what a single interferometer could provide
3Measurement precision
If interferometer switching is performed at constant velocity, then switching errors are reduced, but productivity decreases due to inability to accelerate
Solution Approach 1:
The patent changes the operational parameter from constant velocity to variable velocity operation by introducing acceleration-based correction values. This allows the stage to accelerate and decelerate during interferometer switching while maintaining measurement precision through real-time correction, thereby improving productivity without sacrificing switching accuracy
Solution Approach 2:
The patent implements feedback by continuously monitoring the stage acceleration and using this information to apply appropriate correction values during interferometer switching. The system feeds back the acceleration state to the correction mechanism, creating a closed-loop control that maintains precision despite dynamic operating conditions and enables higher throughput
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 effectively suppresses measurement errors caused by stage acceleration/deceleration, enhancing the accuracy and throughput of semiconductor exposure apparatuses by accurately determining the initial values for interferometer switching, thereby maintaining precise positioning during high-velocity and high-acceleration stages.
Implementation Method 1
incorporates an interferometer for measuring the position of the stage
Implementation Method 2
the shape of the mirror irradiated with a laser beam changes between the acceleration time, the constant velocity time, and the stop time
Data Source
AI summary
A positioning apparatus, which positions a stage, includes a measurement system that measures a position of the stage. The measurement system includes a plurality of measuring devices that are spaced apart from each other along a first direction and measure a position of the stage in a second direction. A switching unit switches between the measuring devices to measure the position of the stage when the stage moves in at least the first direction. A correction unit corrects, based on an acceleration of the stage, the value measured by the measurement system. When the switching unit switches between the plurality of measuring devices, the correction unit corrects, based on a value obtained by the correction, a value measured by a measuring device after the switching.