Imprint Detection Device Pupil Light Blocking for Noise Reduction
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Solution Overview
Problem
The detection accuracy of relative positions between marks on a substrate and a mold in imprint apparatuses is compromised due to noise light from the edges of diffraction gratings, especially when the mark area is reduced, leading to decreased precision in alignment and pattern transfer.
Innovation Solution
A detection device utilizing an illumination system with unpolarized light and a detection system with an image sensor, combined with a light blocking body on the pupil surface to block noise light, allowing for accurate detection of relative positions between diffraction gratings on the substrate and mold by forming optical information representing the relative position in specific directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the mark area is reduced, then the detection accuracy of relative position is improved, but the influence of noise light increases and detection accuracy decreases
Solution Approach 1:
The invention segments the detection process by separating the useful diffracted light from the harmful noise light through the light blocking body. The light blocking body divides the detection field into regions that capture only the desired diffraction signals while excluding noise from mark edges, enabling accurate detection even with reduced mark area.
Solution Approach 2:
The light blocking body acts as an intermediary element between the marks and the image sensor. It selectively blocks noise light paths while allowing useful diffracted light to reach the sensor, thereby mediating the detection process to achieve high accuracy with small mark areas.
2Measurement precision
If a light blocking body is added to block noise light, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The invention extracts and removes the harmful noise light component from the optical path using the light blocking body, while preserving the useful signal. This selective extraction approach improves detection accuracy without requiring complete system redesign.
Solution Approach 2:
The light blocking body is strategically positioned at the pupil surface where it locally affects only the noise light paths. This localized intervention blocks harmful light while leaving the useful diffracted light unaffected, achieving high detection accuracy with a simple added component rather than complex system-wide changes.
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 the detection accuracy of relative positions between diffraction gratings, improving the alignment and pattern transfer precision in imprint apparatuses by minimizing the impact of noise light from the edges of the diffraction gratings.
Implementation Method 1
form an image on an imaging surface of the image sensor from diffracted lights from the first mark and the second mark illuminated by the illumination system
Implementation Method 2
a light blocking body including a first light blocking portion crossing an optical axis of the detection system in a direction parallel to a third direction and a second light blocking portion crossing the optical axis of the detection system in a direction parallel to a fourth direction is provided on a pupil surface of the detection system
Data Source
AI summary
Detection device detects relative position between overlapping first and second marks. The device includes illumination system configured to illuminate the first and second marks with unpolarized illumination light, detection system having image sensor and configured to form image on imaging surface of the image sensor from diffracted lights from the first and second marks. The first and second marks are configured to form, on the imaging surface, optical information representing the relative position in first or second direction. Light blocking body arranged on pupil surface of the detection system includes first light blocking portion crossing the optical axis of the detection system in direction conjugate to the first direction and second light blocking portion crossing the optical axis of the detection system in fourth direction conjugate to the second direction.