Semiconductor Wafer Mark Center Detection by Peak Reversal
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Solution Overview
Problem
Existing methods for detecting crystal orientation marks on semiconductor wafers suffer from inaccurate alignment due to the predetermined width of the marks, leading to rough positioning and potential errors from temporal changes in photoelectric sensors.
Innovation Solution
A method involving rotating the semiconductor wafer relative to measurement light, detecting the maximum light intensity, and reversing the rotation direction when intensity decreases, allowing precise determination of the mark's center without setting a threshold, enhancing positioning accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a threshold method is used to detect the mark center, then the detection process is simple, but the positioning accuracy is poor due to the predetermined width of the mark
Solution Approach 1:
Instead of stopping when the light intensity exceeds a threshold (conventional method), the invention continues rotation past the peak and stops when the light intensity starts decreasing after reaching maximum value. This inversion of the stopping condition allows precise identification of the mark center by detecting the peak position rather than a threshold crossing point.
Solution Approach 2:
The invention changes the detection parameter from threshold-based detection to peak-based detection. By monitoring the maximum light intensity value and its change trend (increasing vs. decreasing), the system achieves higher precision in mark center detection without being constrained by the mark's predetermined width.
2Measurement precision
If the threshold is set closer to the peak value to minimize errors, then the positioning accuracy improves, but erroneous detections occur due to temporal changes in the photoelectric sensor
Solution Approach 1:
The system continuously monitors the light intensity变化趋势 (change trend) during rotation and uses this feedback to determine when to stop. By detecting whether the intensity is increasing or decreasing relative to the maximum value, the system can reliably identify the peak position without being affected by temporal sensor drift or noise that would plague threshold-based methods.
3Productivity
If the wafer is stopped when light intensity exceeds threshold, then the alignment is completed, but the positioning accuracy is rough due to mark width
Solution Approach 1:
The invention inverts the stopping logic: instead of stopping at threshold entry, it stops at peak detection. This allows the system to quickly rotate through the mark position and accurately identify the center by detecting when maximum intensity is reached and begins to decrease, achieving both speed and precision.
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 minimizes errors in detecting the center of crystal orientation marks, improving positioning accuracy and enabling more precise alignment for subsequent processing stages.
Implementation Method 1
receiving the measurement light transmitted or reflected by the mark
Data Source
AI summary
There is provided a detection method for detecting a mark that is formed at an outer peripheral edge of a semiconductor wafer. The detection method includes rotating the semiconductor wafer relative to measurement light in one direction, receiving the measurement light transmitted or reflected by the mark, and detecting that received light intensity of the measurement light has started decreasing after reaching a maximum value, then rotating the semiconductor wafer relative to the measurement light in an opposite direction and receiving the measurement light transmitted or reflected by the mark, determining an area where the received light intensity of the measurement light takes the maximum value as a center of the mark, and, after the rotating the semiconductor wafer relative to the measurement light in the opposite direction and receiving the measurement light transmitted or reflected by the mark, stopping the rotation at the center of the mark.