Pre-Alignment Imaging Sensor With Coaxial Illumination for Tilt Detection
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Solution Overview
Problem
The transfer of a patterning device to an electrostatic chuck can result in damage due to improper relative tilt, leading to inaccuracies and increased costs in the patterning process, particularly in lithographic apparatuses used for manufacturing semiconductor devices.
Innovation Solution
A pre-alignment imaging sensor system with build-in coaxial illumination is employed, utilizing multiple illumination sources and light reflectors to detect the location, orientation, and tilt of the patterning device, ensuring accurate alignment and minimizing contact forces during transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple separate illumination sources are used to detect location, orientation, and tilt, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple separate illumination sources into a single integrated illumination source that provides both coaxial illumination for location detection and oblique illumination for tilt detection. This merging reduces the number of separate components while maintaining the capability to detect all alignment parameters (location, orientation, and tilt) through a unified optical path.
Solution Approach 2:
The single illumination source is designed to perform multiple functions: it provides coaxial illumination for detecting the lateral position of the patterning device and oblique illumination for detecting tilt and orientation. This multi-functional design eliminates the need for separate illumination systems for different measurement purposes.
2Device complexity
If coaxial illumination is used, then device complexity is reduced, but measurement precision may deteriorate due to insufficient separation of illumination and detection paths
Solution Approach 1:
The patent introduces angular separation as an additional dimension to distinguish between different measurement functions. While the illumination source is positioned coaxially with the detection path, it provides illumination at different angles (coaxial and oblique) to enable separate detection of location and tilt parameters through the same optical path.
Solution Approach 2:
The patent uses an intermediary optical element (such as a beam splitter or dichroic mirror) to separate the reflected light into different detection paths based on the illumination angle. This intermediary component enables the system to distinguish between coaxially reflected light (for location detection) and obliquely reflected light (for tilt detection) even though they originate from the same illumination source.
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 system enhances patterning accuracy by protecting the patterning device and electrostatic chuck, reducing damage and processing delays, while simplifying the setup of illumination sources and reducing the number of required light sources.
Implementation Method 1
an object lens group channel along the normal direction configured to receive a 0th order refracted beam from the patterning device
Implementation Method 2
a first light reflector configured to redirect the 0th order refracted beam to form a first retroreflected beam
Data Source
AI summary
A patterning device pre-alignment sensor system is disclosed. The system comprises at least one illumination source configured to provide an incident beam along a normal direction towards a patterning device. The system further comprises an object lens group channel along the normal direction configured to receive a 0th order refracted beam from the patterning device. The system further comprises a first light reflector configured to redirect the 0th order refracted beam to form a first retroreflected beam. The system further comprises a first image lens group channel configured to transmit the first retroreflected beam to a first light sensor. The first light sensor is configured to detect the first retroreflected beam to determine a location feature of the patterning device.