Substrate Alignment Using Superimposed Marks at Fixed Focus
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Solution Overview
Problem
Existing alignment methods for substrates in the semiconductor industry face challenges such as contamination, increased alignment errors due to refocusing, and inability to meet high accuracy requirements, especially when aligning opaque substrates face-to-face.
Innovation Solution
A method and device that utilize alignment marks arranged one above the other on a substrate holder, allowing detection of multiple marks without refocusing by maintaining a fixed focus position, using a detection unit to align substrates with precision by detecting superimposed alignment marks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a camera is positioned between substrates to detect alignment marks, then alignment marks can be detected from outer surfaces, but particles are deposited from the camera onto substrate surfaces and alignment errors increase due to larger travel distances
Solution Approach 1:
The patent introduces a transparent substrate holder as an intermediary component that allows optical detection of alignment marks without requiring the camera to be positioned between the substrates. The transparent holder transmits electromagnetic radiation while supporting the substrate, enabling detection through the holder rather than through the substrate gap, thus avoiding particle deposition from the camera onto substrate surfaces.
Solution Approach 2:
The patent transitions from detecting alignment marks through the substrate gap (z-dimension) to detecting them through the substrate holder surface (x-y plane). By positioning the camera to detect alignment marks on the holder surface rather than through the substrate stack, the system eliminates the need for large z-distance travel while avoiding particle contamination.
2Measurement precision
If the detection unit refocuses during alignment movements, then the focal point can be adjusted, but the focal point shifts in the xy plane causing deviations from ideal movement and reducing alignment accuracy
Solution Approach 1:
The patent performs preliminary focusing on the substrate holder surface before alignment movements begin. By establishing the correct focal plane on the transparent holder surface in advance, the detection unit maintains this fixed focus position throughout the alignment process, eliminating the need for refocusing during movements and preventing focal point shifts in the xy plane.
Solution Approach 2:
The transparent substrate holder serves as a stable intermediary reference surface for focusing. The detection unit focuses on the holder surface which remains stationary during alignment movements, providing a stable focal reference that eliminates the need for refocusing and prevents the focal point shift problems that occur when focusing on moving substrates.
3Productivity
If substrates are measured relative to reference points and blindly aligned after initial approach, then alignment can be completed, but the method fails to meet increasing alignment accuracy requirements
Solution Approach 1:
The patent uses the transparent substrate holder as an intermediary reference surface that enables direct visual and optical detection of alignment marks during the alignment process. This eliminates the need for blind alignment after initial approach, as the holder surface provides a stable reference plane for continuous detection and adjustment, meeting high accuracy requirements while maintaining productivity.
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
Enables precise alignment of opaque substrates with reduced contamination risk and improved accuracy by eliminating the need for refocusing, facilitating reliable and accurate bonding processes.
Implementation Method 1
the alignment marks are detected through the back of the substrate, which is transparent to the electromagnetic radiation used for this purpose
Implementation Method 2
the substrate to be aligned is opaque to the electromagnetic radiation used for detecting the alignment marks of a first and second substrate
Data Source
Figure 1
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AI summary
The invention relates to a method and a device for aligning a substrate.