Optical Alignment System for Substrate Bonding Precision
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Solution Overview
Problem
Conventional substrate bonding machines have limited accuracy, requiring large contact pads and mechanical alignment without considering device locations, which can lead to inaccuracies and inefficiencies in substrate alignment for bonding.
Innovation Solution
An optical alignment system using first and second optical arms to direct radiation from alignment marks on substrates onto a detector, allowing for precise alignment of substrates based on known locations relative to functional patterns, enabling accurate bonding without the need for large contact pads or expensive location monitoring equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional mechanical alignment is used, then the alignment process is simple, but the alignment precision is insufficient (about 100 micrometers)
Solution Approach 1:
The patent replaces the conventional mechanical alignment system with an optical alignment system that uses lasers, optical arms, and detectors to achieve precise alignment. The optical system directs radiation from alignment marks on substrates onto detectors, enabling alignment precision significantly better than the 100 micrometer mechanical limit.
Solution Approach 2:
The patent uses alignment marks that are fabricated copies or references positioned at known locations on substrates. These marks serve as optical copies of the intended contact pad positions, allowing the optical system to detect and correct alignment deviations by comparing the actual mark positions with their designed locations.
2Reliability
If large contact pads are used to compensate for alignment inaccuracy, then alignment tolerance is improved, but the substrate area available for devices is reduced
Solution Approach 1:
By replacing mechanical alignment with optical alignment, the system achieves sub-micrometer to micrometer level alignment precision, eliminating the need for large contact pads as a compensation mechanism. This allows contact pads to be minimized to their functional minimum size.
Solution Approach 2:
The optical alignment system provides real-time feedback on alignment status by detecting the positions of alignment marks. This feedback enables dynamic adjustment of substrate positions to achieve precise alignment, ensuring reliable contact pad connections without requiring oversized pads.
3Measurement precision
If infrared light alignment is used, then alignment precision is improved, but the substrate must be transparent to infrared light
Solution Approach 1:
The patent changes the wavelength parameter of the alignment radiation from infrared to visible or other wavelengths that are transparent to a broader range of substrate materials. This allows the alignment system to work with various substrate types including silicon, glass, and other materials that may not be infrared transparent.
Solution Approach 2:
The optical alignment system is designed to be universally applicable to different substrate materials by using radiation wavelengths that can penetrate or reflect from various materials. The system can accommodate different substrate types without requiring material-specific modifications.
4Measurement precision
If the alternative alignment approach with substrate movement is used, then alignment precision is improved, but the process time increases and expensive equipment is required
Solution Approach 1:
The alignment marks are pre-fabricated on the substrates at known locations relative to functional patterns during the manufacturing process. This preliminary action eliminates the need for complex real-time substrate manipulation and monitoring, as the marks are already in place to guide the alignment process.
Solution Approach 2:
The system uses optical copies (alignment marks) that remain on the substrates throughout the process, eliminating the need to physically move and reposition substrates for alignment verification. The marks serve as permanent references that can be detected without substrate manipulation.
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 optical alignment system achieves accurate substrate alignment, allowing for precise bonding with smaller contact areas and reducing the need for extensive substrate realignment, thereby improving the efficiency and accuracy of substrate bonding processes.
Implementation Method 1
an optical arm arranged to direct radiation from an alignment mark on the substrate onto a detector
Data Source
AI summary
An alignment apparatus for a substrate bonding system is provided with a first optical arm arranged to direct onto a detector radiation from a first alignment mark on a first substrate, and a second optical arm arranged to direct onto the detector radiation from a second alignment mark on a second substrate. The first alignment mark has a known location relative to a functional pattern provided on an opposite side of the first substrate, and the second alignment mark has a known location relative to a functional pattern provided on an opposite side of the second substrate. The substrate bonding system can be further provided with first and second substrate tables arranged to hold the first and second substrates such that they face one another, at least one of the substrate tables being movable in response to a signal output from the detector, thereby allowing the first and second substrates to be aligned with respect to each other for bonding.