Exposure Apparatus Encoder Segmentation for Positioning Accuracy
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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 conventional interferometer systems struggle to mitigate, especially as substrate sizes increase, leading to difficulties in maintaining precise position control and requiring extensive scale lengths that are costly and complex to manage.
Innovation Solution
The exposure apparatus employs a system with multiple measuring sections arranged at different positions to track the movement of both the mask and substrate in orthogonal directions, using encoder heads and scales to maintain position information without relying on long optical paths, thereby reducing air fluctuation effects and eliminating the need for heavy bar mirrors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If an optical interferometer system with a long bar mirror is used to measure the position of large substrates, then the measurement range can cover the entire moving range of the substrate, but the measurement precision deteriorates due to air fluctuation effects
Solution Approach 1:
The patent divides the measurement system into multiple encoder units, each with its own scale and readout heads. Instead of using a single long bar mirror, the system segments the measurement function across multiple smaller encoder units that can be distributed throughout the substrate area, eliminating the need for a single long optical path that is susceptible to air fluctuation
Solution Approach 2:
The patent replaces the optical interferometer system with mechanical encoder units that use physical scales and readout heads. This substitution eliminates the long optical paths and bar mirrors that are vulnerable to air fluctuation, using instead a mechanical measurement approach that is less sensitive to environmental conditions
2Area of stationary object
If a long bar mirror is used in the optical interferometer system to cover the entire substrate moving range, then the measurement range is sufficient, but the device complexity and cost increase
Solution Approach 1:
The measurement system is segmented into multiple independent encoder units, each with its own scale and readout heads. This segmentation eliminates the need for a single long bar mirror and complex optical interferometer, replacing it with simpler, modular encoder units that are easier to implement and maintain
Solution Approach 2:
Instead of extending the measurement system in one dimension with a long bar mirror, the patent distributes multiple encoder units throughout the measurement space. This spatial distribution approach covers the entire substrate area without requiring any single component to be excessively long or complex
3Loss of information
If conventional interferometer systems are used for positioning, then position information can be obtained, but air fluctuation causes harmful effects on measurement accuracy
Solution Approach 1:
The patent replaces the optical interferometer system with mechanical encoder units that use physical scales and readout heads. This substitution eliminates the long optical paths that are vulnerable to air fluctuation, using instead a mechanical measurement approach that is less sensitive to environmental conditions
Solution Approach 2:
The patent introduces encoder scales as intermediary elements between the measurement system and the substrate. These scales serve as physical references that can be read by nearby readout heads without requiring long optical paths, thereby mediating the measurement process in a way that reduces susceptibility to air fluctuation
Data Source
AI summary
A liquid crystal exposure apparatus that irradiates a substrate held by a substrate holder which moves along an XY plane with an illumination light via an optical system while the substrate holder moves in the X-axis direction, has; a scale measured based on movement of the substrate holder in the X-axis direction, heads that measure the scale while relatively moving in the X-axis direction with respect to the scale, a plurality of scales arranged at mutually different positions in the X-axis direction measured based on movement of the substrate holder in the Y-axis direction, and a plurality of heads provided for each scale that measures the scales while relatively moving in the Y-axis direction with respect to the scales based on movement of the substrate in the Y-axis direction.