Dual-Stage Lithography Apparatus Position Control
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Solution Overview
Problem
In lithography processes for semiconductor and liquid crystal display device manufacturing, the focus margin is insufficient due to the narrow depth of focus caused by shorter exposure light wavelengths and larger numerical apertures, leading to potential exposure defects and position control errors in stage positioning.
Innovation Solution
A scanning exposure apparatus with a dual-stage system, where one stage is dedicated to wafer exposure and another for measurement, utilizing a combination of interferometers and encoders with gratings to stabilize position control and improve focus accuracy, allowing for simultaneous measurement and exposure operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the wafer stage is downsized to improve position controllability, then position controllability is improved, but the throughput decreases due to sequential operations
Solution Approach 1:
The patent combines the wafer stage and measurement stage into a single integrated system where both stages can operate simultaneously. The aerial image measuring unit spans both stages, allowing position measurements to be performed on the wafer stage while exposure operations proceed, thereby maintaining high position controllability while improving throughput through parallel operations.
Solution Approach 2:
The measurement and exposure operations are made continuous rather than sequential. While the wafer stage performs exposure operations, the measurement stage simultaneously performs position measurements and aerial image measurements. This continuity eliminates idle time and maintains high productivity while ensuring accurate position control.
2Measurement precision
If separate stages are used for measurement and exposure, then measurement capability is improved, but focus leveling control error occurs due to stage differences
Solution Approach 1:
The aerial image measuring unit provides real-time feedback about the aerial image characteristics at multiple positions. This feedback is used to determine focus characteristics and make corrections to the focus leveling control. By continuously monitoring and adjusting based on actual measurements, the system compensates for differences between measurement and exposure stages, maintaining high measurement capability while ensuring accurate focus control.
3Measurement precision
If laser interferometer is used for position measurement, then measurement resolution is improved, but short-term fluctuation increases due to temperature fluctuations
Solution Approach 1:
The position measurement system is segmented into multiple measurement points distributed across both the wafer stage and measurement stage. By measuring at multiple locations simultaneously, the system can identify and compensate for temperature-induced fluctuations in the laser interferometer readings, maintaining high resolution while improving stability through spatial diversification of measurements.
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 configuration enhances position control stability and focus accuracy, reducing exposure defects by enabling precise measurement and adjustment during the exposure process, even with shorter wavelengths and larger numerical apertures.
Implementation Method 1
position measurement of the wafer stage is generally performed using a laser interferometer
Implementation Method 2
encoders with gratings to stabilize position control
Data Source
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AI summary
An exposure apparatus for exposing a substrate with an illumination light via a projection optical system and a liquid comprises a nozzle member (32), an alignment system (AL1), a mask stage system having a first stage (RST), a base member (12) disposed below the projection optical system, a substrate stage system having a second stage (WST) and a third stage (MST) that are disposed on the base member, a measurement system having a plurality of heads arranged for respectively irradiating a plurality of scale members, and a controller configured to control the first and the second drive systems so that, in an exposure operation of the substrate, scanning exposure in which the mask and the substrate are each moved relative to the illumination light is performed.