Detector With Multi-Direction Illumination For Imprint Alignment
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Solution Overview
Problem
Existing imprint apparatuses struggle to accurately detect the relative positions of a mold and a substrate in multiple directions using a single detector, as they rely on oblique illumination and detection of diffracted light, which limits the acquisition of positional information in various directions.
Innovation Solution
A detector system with an illumination optical system that forms a light intensity distribution with poles in both x and y directions, allowing diffracted light components from marks on the mold and substrate to be detected by a single detection optical system, enabling accurate alignment in both x and y directions by utilizing grating patterns with different pitches and oblique illumination to generate moire fringes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single detector uses oblique illumination to detect diffracted light from alignment marks, then the detection system can be simplified, but the ability to acquire positional information in multiple directions is limited
Solution Approach 1:
The illumination optical system is divided into multiple independent illumination sources (first illumination source and second illumination source) that can be controlled separately. Each illumination source is configured to illuminate alignment marks in different directions, allowing the single detector to receive diffracted light components from multiple directions simultaneously. This segmentation of the illumination system enables multi-directional positional information acquisition without increasing detector complexity.
Solution Approach 2:
The patent introduces a new dimension of control by making the illumination sources controllable in terms of on/off states and illumination directions. The first illumination source can illuminate in a first direction while the second illumination source illuminates in a second direction, creating a multi-dimensional illumination space. This allows the detector to capture positional information in multiple directions through a single detection system, effectively adding dimensional capability to the detection process.
2Measurement precision
If grating patterns with different grating pitches are used on mold and substrate, then moire fringe can be generated for high-accuracy alignment, but the detection requires complex optical systems
Solution Approach 1:
The optical system is segmented into distinct functional components: the first illumination source with first illumination optical system, the second illumination source with second illumination optical system, and the detector with detection optical system. Each component is optimized for specific functions - the illumination sources generate moire fringes while the detector captures them. This segmentation allows the system to achieve high measurement precision through moire fringe analysis without requiring a single complex optical system, as each component can be designed and optimized independently.
Solution Approach 2:
The moire fringe pattern acts as an intermediary that converts the complex task of direct high-precision position measurement into a simpler fringe pattern analysis problem. By using grating patterns with different pitches on the mold and substrate, the system generates moire fringes that amplify positional differences. The detector then measures the fringe patterns rather than directly measuring positions, which simplifies the optical system requirements while maintaining high measurement precision.
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 allows for precise alignment of the mold and substrate in both x and y directions, even with a detection optical system of low resolving power, enhancing the accuracy and efficiency of the imprint process.
Implementation Method 1
Light obliquely incident on the marks is diffracted in the non-measurement direction by a checkerboard grating pattern formed on the substrate
Implementation Method 2
the interference between diffracted light components from the two grating patterns forms an interference fringe (a so-called moire fringe)
Data Source
AI summary
A detector includes an illumination optical system that illuminates a first diffraction grating having a period in each of a first direction and a second direction different from the first direction, and a second diffraction grating having a period in the second direction different from the period of the first diffraction grating in the second direction. A detection optical system detects diffracted light diffracted by the first diffraction grating and the second diffraction grating. The detection optical system includes a photoelectric conversion element and a guide portion arranged on a pupil plane of the detection optical system. The guide portion guides, to the photoelectric conversion element, the light diffracted by the first diffracting grating and the second diffraction grating. The diffracted light diffracted by the second diffraction grating enters a position different from the guide portion on the pupil plane of the detection optical system.