Dipole Illumination Orthogonal Polarization Alignment Detection
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Solution Overview
Problem
Existing imprint techniques using photo-curing methods face challenges in achieving accurate alignment between the substrate and the mold due to interference fringes generated by two-beam interference, which degrade the accuracy of alignment measurement.
Innovation Solution
A detection apparatus is developed that utilizes a dipole illumination system with orthogonal polarization directions for the two poles in the pupil plane, and a detection optical system to detect interference light formed by diffracted light from alignment marks on the mold and substrate, thereby reducing two-beam interference and improving alignment measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dipole illumination is used to generate moire fringes for alignment measurement, then alignment detection is enabled, but two-beam interference generates interference fringes that degrade measurement accuracy
Solution Approach 1:
The patent changes the polarization state parameter of the illumination light by introducing a polarization plate that converts linearly polarized light from the laser source into circularly polarized light. This parameter change eliminates two-beam interference because circularly polarized light does not produce interference fringes when reflected from the wafer surface, thereby removing the harmful interference fringes while maintaining the moire fringe pattern needed for alignment measurement
Solution Approach 2:
The patent converts the potentially harmful linear polarization state into a beneficial circular polarization state. By using a quarter-wave plate or similar optical element to transform the polarization, the system eliminates the interference problem while preserving the alignment measurement capability, effectively turning a harmful factor into a beneficial solution
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
The proposed solution enhances the stability of detection accuracy by minimizing the impact of interference fringes, leading to improved precision in aligning the mold and substrate during the imprint process.
Implementation Method 1
the illumination optical system performs dipole illumination by light including two poles in a pupil plane of the illumination optical system
Implementation Method 2
polarization directions of light beams emitted from the two poles, respectively, and incident on the substrate are orthogonal to each other
Implementation Method 3
a detection optical system configured to detect interference light formed by diffracted light diffracted by the first diffraction grating and diffracted light diffracted by the second diffraction grating
Implementation Method 4
detection optical system configured to detect interference light formed by diffracted light diffracted by the first diffraction grating and diffracted light diffracted by the second diffraction grating
Data Source
AI summary
A detection apparatus that detects a position deviation between an original and a substrate is provided. The apparatus includes an illumination optical system configured to illuminate a first diffraction grating arranged on the original and a second diffraction grating arranged on the substrate, and a detection optical system configured to detect interference light formed by diffracted light diffracted by the first diffraction grating and diffracted light diffracted by the second diffraction grating. The illumination optical system performs dipole illumination by light including two poles in a pupil plane of the illumination optical system, and polarization directions of light beams emitted from the two poles, respectively, and incident on the substrate are orthogonal to each other.