Magnetic Sensor Calibration for Planar Motor Stage Control
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Solution Overview
Problem
Existing stage control systems in exposure apparatuses face controllability issues due to the loss of valid interferometer or encoder signals during initialization or operation, which affects the precision and stability of stage movement.
Innovation Solution
A stage assembly that incorporates a magnetic sensor system, including Hall sensors, for six-degree-of-freedom control, which is calibrated using methods such as sensor decoupling from coil flux, offset removal, gain equalization, and correction maps, allowing it to take over when interferometer or encoder signals are lost, ensuring continuous stage control and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If interferometer or encoder systems are used as primary measurement systems, then measurement precision is improved, but reliability deteriorates due to signal loss during initialization or operation
Solution Approach 1:
The patent changes the operational parameters of the magnetic sensors through calibration processes including offset removal, gain equalization, and correction map generation. These parameter adjustments enable the magnetic sensor system to achieve sufficient accuracy for servo control while providing reliable operation independent of interferometer or encoder signals.
Solution Approach 2:
The magnetic sensor system acts as an intermediary measurement system that bridges the gap between the primary interferometer/encoder system and the servo control system. During initialization or when primary signals are lost, the calibrated magnetic sensors provide continuous position feedback, ensuring uninterrupted stage control and maintaining system reliability.
2Difficulty of detecting and measuring
If magnetic sensors are positioned close to coils for monitoring, then measurement capability is improved, but measurement precision deteriorates due to coil flux interference
Solution Approach 1:
The patent extracts the harmful coil flux interference from the magnetic sensor measurements through calibration procedures. By measuring and characterizing the coil flux contribution during calibration, the system can subtract this interference from the raw sensor signals, leaving only the true position-dependent magnetic field components for accurate measurement.
Solution Approach 2:
The patent performs preliminary calibration actions before normal operation to prepare the magnetic sensor system for accurate measurement. The calibration process includes measuring coil flux interference, generating correction maps, and establishing offset and gain parameters in advance, so that during operation the sensors can provide precise measurements despite their proximity to the coils.
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
The calibrated magnetic sensor system enables precise and stable stage movement even when primary measurement systems are unavailable, maintaining high accuracy and reliability in positioning and trajectory control.
Implementation Method 1
the magnetic sensor is a hall sensor
Data Source
AI summary
A stage assembly for positioning a device includes: (i) a stage that retains the device; (ii) a base; (iii) a mover assembly that moves the stage along a first axis, along a second axis, and along a third axis relative to the base; (iv) a magnetic sensor system that monitors the movement of the stage along the first, second and third axes, the magnetic sensor system generating a magnetic sensor signal; (v) a second sensor system that monitors the movement of the stage along the first, second and third axes, the second sensor system generating a second sensor signal; and (vi) a control system that controls the mover assembly using at least one of the magnetic sensor signal and the second sensor signal.