Wafer Bond Alignment Imaging Using Displacement-Based Focus
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Solution Overview
Problem
Conventional methods for measuring position deviation between bonded semiconductor wafers require multiple focus adjustments due to varying substrate thickness, leading to inefficient imaging and prolonged measurement times.
Innovation Solution
A measuring device with an imaging unit and displacement meter that allows for efficient focusing on measurement marks within the combined substrate by moving the focal position based on pre-set displacement measurements, reducing the range of focus adjustments needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple focus adjustments are performed to account for varying substrate thickness, then imaging accuracy is improved, but measurement time increases
Solution Approach 1:
The patent measures the distance from the substrate surface to the measurement mark before imaging. This preliminary distance measurement allows the system to pre-calculate the optimal focal position, eliminating the need for multiple focus adjustments during imaging while maintaining accurate focus on the measurement mark
Solution Approach 2:
The patent replaces the mechanical focus adjustment process with a calculation-based approach. By using the measured distance and optical parameters to compute the focal position mathematically, the system substitutes iterative mechanical focusing with a direct calculated positioning method, significantly reducing measurement time
2Productivity
If the focal position is set based on average substrate thickness, then imaging speed is improved, but positioning accuracy deteriorates
Solution Approach 1:
The patent transitions from using a global average thickness value to measuring and using the local distance from the substrate surface to the measurement mark at the specific imaging location. This localized measurement ensures accurate focal positioning for each specific substrate, maintaining precision while enabling direct calculation-based focusing that improves speed
3Measurement precision
If manual focus adjustment is performed for each substrate, then imaging accuracy is maintained, but operational complexity increases
Solution Approach 1:
The patent implements an automated system where the imaging unit automatically obtains the distance measurement, calculates the optimal focal position using stored optical parameters, and adjusts focus without manual intervention. The system serves itself by integrating measurement and calculation functions that automatically determine and execute the correct focal setting
Solution Approach 2:
The patent uses the measured distance from the substrate surface as feedback to calculate and adjust the focal position. This feedback mechanism creates a closed-loop system where the actual substrate characteristics directly determine the focusing parameters, eliminating the need for manual adjustment while maintaining accuracy
Data Source
AI summary
A measuring method includes measuring a displacement A1, placing an imaging unit 20 at a position where the imaging unit is allowed to image a measurement mark MI and imaging the measurement mark M1. In the measuring of the displacement A1, the displacement A1 of a surface of a combined substrate, which is composed of two sheets of substrates bonded to each other, on a side of the imaging unit 20 at a position where the measurement mark M1 for position deviation measurement, which is provided within the combined substrate, is placed is measured. In the imaging of the measurement mark M1, the measurement mark M1 is imaged by the imaging unit 20 while putting the measurement mark M1 in focus by moving a focal position back and forth with respect to a focal position which is previously set based on the displacement A1.