Wafer Bonding Alignment via Moiré Pattern Distance Detection
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Solution Overview
Problem
Current wafer bonding methods lack precise alignment due to limitations in detecting distance and inclination between wafers, particularly when using infrared light for inspection, which results in suboptimal bonding precision.
Innovation Solution
A method and apparatus that utilize overlapping grid patterns on wafers to form Moiré patterns with infrared light, allowing for the calculation of distances and adjustment of inclination between wafers, enhancing alignment precision through the detection of maximum contrast wavelengths and relative movement of wafer holders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If infrared light is used for alignment inspection, then the inspection method is inexpensive and simple, but the optical spatial resolution deteriorates
Solution Approach 1:
The patent introduces Moiré patterns as an intermediary mechanism to bridge the gap between infrared light's long wavelength (poor resolution) and the need for precise alignment measurement. By using overlapping grid patterns that generate Moiré fringes, the system can detect sub-pixel displacements and achieve high measurement precision despite the limitations of infrared illumination
Solution Approach 2:
The patent changes the measurement parameter from direct optical resolution to Moiré fringe analysis. Instead of relying on the inherent resolution of infrared light, the system uses wavelength calculation based on Moiré pattern characteristics, transforming the measurement approach to overcome the wavelength limitation
2Measurement precision
If Moiré pattern technique is used for fine alignment, then the alignment precision is improved, but the distance and inclination between wafers cannot be detected
Solution Approach 1:
The patent segments the alignment measurement into multiple independent measurements at different wavelengths. By performing alignment inspections at multiple infrared wavelengths and analyzing the Moiré patterns at each wavelength, the system can extract both lateral alignment information and depth/distance information through wavelength-dependent phase analysis
Solution Approach 2:
The patent adds the wavelength dimension to the measurement space. By measuring Moiré patterns at multiple wavelengths, the system transforms a 2D alignment problem into a 3D measurement problem, enabling detection of distance and inclination in addition to lateral alignment through the wavelength-dependent optical path difference
3Measurement precision
If multiple wavelengths are used for Moiré pattern detection, then the distance and inclination measurement accuracy is improved, but the alignment process complexity increases
Solution Approach 1:
The patent implements a feedback-based iterative alignment process. The system performs alignment inspections at multiple wavelengths, uses the Moiré pattern data to calculate wavelength and determine misalignment, then adjusts the wafer position and repeats the measurement until optimal alignment is achieved. This feedback loop automates the complex multi-wavelength measurement process
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 improves wafer bonding precision by accurately determining distances and adjusting inclinations, leading to more precise alignment and bonding of wafers, thereby enhancing the quality of semiconductor devices.
Implementation Method 1
irradiating a first infrared light onto a first grid pattern in a first region of the held first wafer and a second grid pattern in the held second wafer, wherein the first grid pattern and the second grid pattern overlap, detecting a first Moiré pattern formed by the overlapping first and second grid patterns
Data Source
AI summary
A method for adjusting inclination between wafers may include providing a first infrared light onto a first grid pattern in a first region in a first wafer and a second grid pattern in a second wafer, the first and second grid patterns overlapping, calculating a first distance in the first region between the first and second wafers based on a first Moiré pattern from the overlapping first and second grid patterns, providing a second infrared light onto a third grid pattern in a second region in the first wafer and a fourth grid pattern in the second wafer, the third and fourth grid patterns overlapping, calculating a second distance in the second region between the first and second wafers based on a second Moiré pattern from the overlapping third and fourth grid patterns, and adjusting relative inclination between the first and second wafers based on the first and second distances.