Dual-Camera Positioning Calibration for Thermal Drift in Wafer Cutting
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Solution Overview
Problem
The existing processing methods for positioning image capturing units in a processing apparatus face challenges in maintaining accurate reference positions due to deviations caused by heat generation, which affects the precision of detecting kerfs in wafers during cutting operations.
Innovation Solution
A method involving a series of coordinate detection and storage steps, followed by deviation calculation and correction, is implemented to align the reference positions of image capturing units on a holding table with a transparent material, ensuring they are coincident on the XY plane, thereby reducing positional deviations and maintaining precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the processing apparatus operates for an extended period, then productivity is improved, but thermal expansion causes deviation between reference positions of image capturing units
Solution Approach 1:
The system performs preliminary positioning of image capturing units before processing operations begin. Reference positions are detected and stored in advance, and correction values are calculated beforehand to compensate for thermal expansion that will occur during operation. This preliminary action ensures that even as the apparatus heats up and components expand, the pre-calculated correction values maintain alignment accuracy throughout the processing sequence.
Solution Approach 2:
The system implements periodic detection and updating of reference positions during operation. Rather than assuming static alignment, the apparatus periodically re-detects the positions of image capturing units relative to the chuck table and updates correction values accordingly. This periodic action compensates for cumulative thermal expansion effects that occur during extended productivity-driven operation sequences.
2Device complexity
If the reference position is fixed initially, then device complexity is reduced, but positional deviation increases due to thermal expansion
Solution Approach 1:
The system transitions from a static reference position model to a dynamic one. Instead of fixing reference positions permanently, the apparatus continuously detects current positions of image capturing units and updates reference position data in real-time. This dynamic approach allows the system to adapt to thermal expansion and other environmental changes without requiring complex mechanical adjustment mechanisms, maintaining precision through software-based adaptability rather than mechanical complexity.
Solution Approach 2:
The system implements feedback loops where the detected positions of image capturing units are continuously monitored and compared against stored reference positions. Correction values are calculated based on detected deviations and fed back to adjust the reference position data. This feedback mechanism automatically compensates for thermal expansion effects, maintaining alignment accuracy without requiring complex manual intervention or mechanical adjustment systems.
3Measurement precision
If multiple image capturing units are used to detect kerfs, then measurement precision is improved, but positional deviation between units reduces reliability
Solution Approach 1:
The system introduces a common reference framework based on the chuck table as an intermediary for all image capturing units. Each unit's position is detected and corrected relative to this common reference, ensuring that all units operate from the same coordinate system. This intermediary reference framework enables multiple image capturing units to work together reliably, maintaining both measurement precision and inter-unit consistency even as thermal expansion occurs during operation.
Data Source
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AI summary
A positioning method includes detecting coordinates (X11, Y11) of a rotation center on a surface of a holding table with a first image capturing unit and stores the detected coordinates as a new first reference position, detecting coordinates (X21, Y21) of a rotation center on another surface of the holding table with a second image capturing unit and stores the detected coordinates as a new second reference position, calculating a first deviation between a previous rotation center on the surface of the holding table and the coordinates (X11, Y11), calculating a second deviation between a previous rotation center on the other surface of the holding table and the coordinates (X22, Y21), correcting a coordinate system of images captured by the first image capturing unit to eliminate the first deviation, and correcting a coordinate system of images captured by the second image capturing unit to eliminate the second deviation.