DMD Optical Alignment System for Imprint Lithography
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Solution Overview
Problem
Current imprint lithography systems face challenges in precise alignment of substrates relative to templates due to the complexity and expense of interferometric devices, and difficulties in obtaining adequate imagery, leading to production defects.
Innovation Solution
An optical system incorporating a digital micromirror device (DMD) and moiré patterns is used for real-time imaging and alignment, allowing for precise positioning of the stage without the need for expensive encoders, by generating and processing moiré patterns to provide alignment feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If interferometric devices are used for alignment, then manufacturing precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces complex mechanical interferometric alignment devices with an optical imaging system using a digital micromirror device (DMD) and camera. The system captures images of alignment marks on the substrate and template, processes these images to generate moiré patterns, and uses these patterns to determine relative positioning. This substitution of mechanical interferometry with optical imaging and digital processing resolves the contradiction by achieving high alignment precision through software-based image analysis rather than complex hardware interferometers.
Solution Approach 2:
The patent creates optical copies (images) of the alignment marks on both the substrate and template using the illuminator and imaging system. These captured images are then processed to generate moiré patterns that encode alignment information. By working with optical copies and digital representations rather than direct mechanical measurement, the system achieves precise alignment measurement without requiring complex physical interferometric devices.
2Manufacturing precision
If interferometric devices are used for alignment, then manufacturing precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent replaces mechanical interferometric devices with an optical imaging system using a digital micromirror device (DMD) and camera. The system captures images of alignment marks on the substrate and template, processes these images to generate moiré patterns, and uses these patterns to determine relative positioning. This substitution of mechanical interferometry with optical imaging and digital processing resolves the contradiction by achieving high alignment precision through software-based image analysis rather than complex hardware interferometers.
3Device complexity
If traditional imaging methods are used, then device complexity is reduced, but manufacturing precision deteriorates
Solution Approach 1:
The patent introduces moiré patterns as an intermediary between the simple optical imaging system and the precise alignment measurement. The imaging system captures images of alignment marks, which are then processed to generate moiré patterns. These moiré patterns serve as an intermediary representation that encodes high-precision alignment information, allowing the simple optical system to achieve measurement precision that would otherwise require complex interferometric hardware.
Solution Approach 2:
The patent transforms the alignment measurement problem by changing the parameter representation from direct coordinate measurement to moiré pattern frequency analysis. By capturing images and processing them to generate moiré patterns, the system converts spatial alignment information into frequency domain characteristics that can be precisely measured and analyzed, enabling high alignment precision through software processing rather than complex hardware.
4Productivity
If alignment convergence time is reduced, then productivity is improved, but measurement precision may deteriorate
Solution Approach 1:
The patent implements continuous real-time imaging and processing of alignment marks during stage movement. The digital micromirror device continuously captures images of the alignment marks, and the system continuously processes these images to generate moiré patterns and update position feedback. This continuous measurement and feedback process allows the alignment convergence to proceed rapidly while maintaining high precision, as the system continuously refines the alignment information rather than relying on discrete slow measurements.
Solution Approach 2:
The patent implements a closed-loop feedback system where the imaging system continuously monitors the relative position of the substrate and template through captured images and generated moiré patterns. This feedback information is used to adjust the stage position in real-time, enabling rapid convergence to the correct alignment while maintaining high precision. The feedback loop allows the system to quickly detect and correct alignment errors, achieving both fast convergence and 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 approach significantly reduces alignment convergence times to sub-5 nanometer levels, stabilizes closed-loop control, and improves feedback loop performance, minimizing production defects by enabling precise and cost-effective alignment of templates and substrates.
Implementation Method 1
An optical system incorporating a digital micromirror device (DMD) and moiré patterns is used for real-time imaging and alignment
Implementation Method 2
by generating and processing moiré patterns to provide alignment feedback
Data Source
AI summary
Imprint lithography benefits from precise alignment between a template and a substrate during imprinting. A moiré signal resulting from indicia on the template and the substrate are acquired by a system comprising a line-scan camera and a digital micromirror device (DMD) which provides a high bandwidth, low-latency signal. Once acquired, the moiré signal may be used directly to align the template and the substrate without need for discrete position/angle encoders.