Movable Body Apparatus Encoder Air Fluctuation Compensation
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Solution Overview
Problem
In lithography processes for manufacturing electronic devices, the precision position control of substrates relative to projection optical systems is hindered by air fluctuations due to long optical paths in existing encoder systems, particularly optical interferometer systems.
Innovation Solution
A movable body apparatus with a grating member and measurement heads that measure position information in multiple directions, using a control system to compensate for measurement errors and maintain precise movement control, thereby reducing the impact of air fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optical interferometer system is used for position measurement, then measurement capability is provided, but air fluctuation causes measurement error
Solution Approach 1:
The patent introduces a grating member as an intermediary element between the measurement heads and the final position measurement. Multiple measurement heads simultaneously measure different grating areas, and the results are combined through coordinate transformation. This intermediary grating system reduces the impact of air fluctuations by distributing measurements across multiple locations and using relative position measurements rather than absolute optical path measurements.
Solution Approach 2:
The patent divides the measurement system into multiple segments: multiple measurement heads (first heads and second heads) that simultaneously measure different grating areas of the grating member. By segmenting the measurement into multiple simultaneous observations and combining them through coordinate transformation, the system reduces the influence of air fluctuations that would affect a single long optical path.
2Reliability
If multiple measurement heads are used to reduce air fluctuation impact, then measurement reliability improves, but device complexity increases
Solution Approach 1:
The grating member serves multiple functions: it is both the measurement target and the reference frame for coordinate transformation. The measurement heads perform dual functions of measuring both the grating member position and the movable body position simultaneously. This multi-functionality reduces the need for separate measurement systems, thereby managing complexity while improving reliability.
Solution Approach 2:
The control system receives position information from multiple measurement heads, performs coordinate transformation to calculate the position of the movable body, and uses this feedback to control the movable body's position. The system continuously monitors and adjusts based on the combined measurements from all heads, improving reliability through real-time feedback while managing complexity through integrated control.
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 enhances the precision of substrate position control, improving exposure accuracy by minimizing the influence of air fluctuations and maintaining high-precision movement within a predetermined plane.
Implementation Method 1
In the case of obtaining position information on the substrate using an optical interferometer system, since the optical path of the laser to the bar mirror becomes long, influence of air fluctuation cannot be ignored.
Data Source
AI summary
A movable body apparatus has: a substrate holder holding a substrate and can move in the X and Y-axes directions; a Y coarse movement stage movable in the Y-axis direction; a first measurement system acquiring position information on the substrate holder by heads on the substrate holder and a scale on the Y coarse movement stage; a second measurement system acquiring position information on the Y coarse movement stage by heads on the Y coarse movement stage and a scale; and a control system controlling the position of the substrate holder based on position information acquired by the first and second measurement systems. The first measurement system irradiates a measurement beam while moving the heads in the X-axis direction with respect to the scale, and the second measurement system irradiates a measurement beam while moving the heads in the Y-axis direction with respect to the scale.