Grating Measurement System for Exposure Apparatus
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Solution Overview
Problem
Conventional exposure apparatuses face challenges in accurately positioning large substrates due to the influence of air fluctuations, which traditional interferometer systems struggle to mitigate effectively, especially as substrate sizes increase, leading to difficulties in maintaining precise positioning and requiring extensive setup and maintenance.
Innovation Solution
An exposure apparatus with a measurement system using a grating member and heads that irradiate measurement beams to measure position information in three degrees of freedom, allowing for precise control of the movable body's movement and reducing the need for large-scale encoders, thereby minimizing air fluctuation effects and simplifying the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optical interferometer system with a bar mirror is used to obtain position information of the substrate, then position measurement capability is provided, but the system becomes complex and vulnerable to air fluctuation effects
Solution Approach 1:
The patent divides the measurement system into multiple independent components: multiple heads (first and second heads) that can be selectively used, and multiple grating areas (first and second grating areas) on the grating member. This segmentation allows the system to measure position information without requiring a single complex interferometer system with large bar mirrors, thereby reducing overall system complexity while maintaining measurement precision.
Solution Approach 2:
The patent replaces the optical interferometer system with a mechanical encoder system using a grating member and measurement heads. Instead of using optical interference patterns and large bar mirrors, the system uses a grating structure with ruled lines that can be read by measurement heads to obtain position information. This substitution eliminates the complexity and air fluctuation sensitivity of optical interferometers while providing robust position measurement capability.
2Reliability
If an encoder system is used to reduce air fluctuation influence, then measurement stability improves, but a large scale is required to cover the entire moving range of the substrate
Solution Approach 1:
The grating member is divided into multiple grating areas (first grating area and second grating area) that can be selectively used. The measurement system includes multiple heads that can measure position information from different grating areas. This segmentation allows the system to cover the entire moving range of the substrate without requiring a single excessively long grating scale, as different grating areas can be activated depending on the substrate position.
Solution Approach 2:
The patent extends the measurement capability in the Y-axis direction by providing multiple grating areas arranged along the Y-axis and multiple heads that can selectively measure from these areas. This dimensional arrangement allows the system to cover large substrate moving ranges without requiring a single long grating scale in the scanning direction, thereby reducing the required scale length while maintaining measurement stability.
3Measurement precision
If multiple grating areas and multiple heads are used to measure position information, then positioning accuracy for large substrates is improved, but the grating member complexity increases
Solution Approach 1:
The grating member is segmented into multiple grating areas (first and second grating areas) with ruled lines arranged in different directions. Each grating area can be independently used for measurement in specific directions. This segmentation provides positioning accuracy in multiple directions without requiring a single complex grating structure, as the system can selectively use appropriate grating areas based on measurement requirements.
Solution Approach 2:
The grating member with multiple grating areas serves multiple measurement functions: it can provide position information in the scanning direction (X-axis) and in the Y-axis direction using different grating areas and corresponding heads. This multi-functionality allows a single grating member structure to replace what would otherwise require separate measurement systems for different directions, thereby improving positioning accuracy without proportionally increasing complexity.
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 positioning accuracy, reduces the complexity and cost of the system, and allows for smaller, lighter, and more maintainable equipment, while eliminating the need for partial air-conditioning and large bar mirrors, improving overall controllability and reducing costs.
Implementation Method 1
a measurement system in which one of a grating member with a plurality of first grating areas arranged mutually apart in the first direction and a plurality of second grating areas arranged apart from the plurality of first grating areas in the second direction and apart from one another in the first direction and a plurality of heads each irradiating the grating member with a measurement beam
Data Source
AI summary
A control system, of a plurality of heads, acquires grating correction information related to at least two of scales in a first grating group and scales in a second grating group, based on position information of a movable body measured using at least four heads irradiating measurement beams on at least two of the scales and scales. The grating correction information is used to control movement of the movable body using at least three heads irradiating at least two of the scales and scales.