Wavelength Separation Element for Optical Alignment in Exposure Apparatus
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Solution Overview
Problem
Existing exposure apparatuses face productivity and accuracy issues due to optical system degradation from exposure light, leading to increased positioning time and reduced alignment mark detection accuracy during semiconductor and liquid crystal display manufacturing.
Innovation Solution
Incorporation of a wavelength separation element, such as a dichroic prism or film, within the optical system to separate exposure light from alignment mark detection light, protecting optical members with high refractive index materials from exposure light-induced solarization and transmissivity degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optical system for alignment mark detection is configured on the substrate stage to perform back surface alignment, then alignment mark detection capability is improved, but exposure light may enter the optical system causing optical characteristic degradation
Solution Approach 1:
The optical system is divided into separate functional components: the alignment mark detection optical system is separated from the exposure optical system. The detection optical system includes specific optical members (lenses, mirrors) that are isolated from direct exposure light paths, while the exposure system handles the high-intensity exposure light separately. This segmentation prevents exposure light from degrading the optical characteristics of detection system components.
Solution Approach 2:
A beam splitter or dichroic mirror is introduced as an intermediary element between the exposure light path and the detection optical system. This intermediary component allows the detection optical system to observe alignment marks while blocking or redirecting exposure light, thereby protecting the optical members from exposure light-induced degradation while maintaining detection functionality.
2Measurement precision
If the optical system for alignment mark detection is positioned to observe alignment marks from the substrate stage side, then detection functionality is achieved, but positioning control time increases due to optical characteristic changes
Solution Approach 1:
The alignment mark detection is performed preliminarily before exposure to establish precise positioning. The detection optical system captures alignment mark positions and provides positioning information to the control system in advance, enabling pre-positioning of the substrate. This preliminary detection action reduces the time required for positioning control during the actual exposure process, as the system has already established accurate positional references.
3Ease of operation
If exposure light irradiates optical members in the alignment mark detection system, then detection is possible, but transmissivity and color of optical members degrade
Solution Approach 1:
The harmful exposure light is extracted or removed from the path of the detection optical system's optical members. The system design ensures that exposure light does not directly irradiate the lenses, mirrors, and other optical components used for alignment mark detection. This extraction of the harmful factor (exposure light) from the detection system protects the optical members from solarization and transmissivity degradation while maintaining detection operation capability.
Solution Approach 2:
The patent employs optical members with specific properties that are resistant to exposure light damage, or uses a detection optical system that can be easily replaced or recalibrated if degradation occurs. The system may use disposable or easily replaceable optical components in the detection path that are less susceptible to exposure light damage, ensuring continuous operation without long-term degradation affecting productivity.
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
Significantly reduces the impact of exposure light on optical members, maintaining alignment mark detection accuracy and productivity by minimizing optical characteristic changes, thus enhancing manufacturing efficiency and quality.
Implementation Method 1
Incorporation of a wavelength separation element, such as a dichroic prism or film, within the optical system to separate exposure light from alignment mark detection light
Data Source
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AI summary
There is provided a pattern forming apparatus including a holding unit configured to suction and hold a substrate, and an optical system configured to detect, from a suction surface side of the substrate, an alignment mark formed on the substrate held by the holding unit. The pattern forming apparatus is provided with a wavelength separation element for performing wavelength separation between pattern forming light for forming a pattern on the substrate and alignment mark detection light for detecting the alignment mark.