Wafer Defect Coordinate Calibration for Accurate LPD Microscopy
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Solution Overview
Problem
The low accuracy of laser surface inspection apparatuses in detecting the position of light point defects (LPDs) on semiconductor wafers, particularly due to significant deviations in the wafer rotation direction, makes it difficult to morphologically observe these defects with a microscope, as they may be outside the observation field or misidentified.
Innovation Solution
A calibration method using a two-dimensional Cartesian coordinate system to determine and correct the coordinate positions of LPDs detected by a laser surface inspection apparatus, by comparing with a reference wafer using a surface defect inspection apparatus equipped with a confocal laser scanning microscope, ensuring positional accuracy within a threshold range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a laser surface inspection apparatus is used to detect LPDs on semiconductor wafer surface by scanning with incident laser light while rotating the wafer, then the detection speed is high, but the position identification accuracy is low due to significant deviations in the wafer rotation direction
Solution Approach 1:
The patent applies preliminary action by performing coordinate calibration before actual LPD detection. A calibration pattern is first detected to establish accurate coordinate transformation relationships, which are then used during subsequent defect detection to ensure high position identification accuracy while maintaining fast detection speeds.
Solution Approach 2:
The patent introduces an intermediary coordinate calibration process that mediates between the laser surface inspection apparatus and the final defect position identification. By using a calibration pattern and establishing coordinate transformation relationships, the system bridges the gap between rapid scanning and precise positioning.
2Productivity
If the LPD detection accuracy is low, then the detection process is fast, but the LPD may be outside the microscope observation field or misidentified, making morphological observation difficult
Solution Approach 1:
The patent implements feedback by using the coordinate calibration information to guide microscope observation. The calibrated coordinate positions provide accurate feedback on where to position the microscope, ensuring that the observed LPDs are exactly those detected by the laser inspection apparatus, thereby avoiding missed observations or misidentifications.
Solution Approach 2:
The patent replaces manual or trial-and-error mechanical positioning with automated coordinate-based positioning. By substituting the mechanical alignment process with computer-controlled coordinate transformation and positioning based on calibration data, the system achieves both high detection efficiency and accurate morphological observation.
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 method improves the accuracy of LPD detection and facilitates morphological observation by ensuring that the detected positions are within the observable range of a microscope, enhancing the precision of defect and foreign matter identification on semiconductor wafers.
Implementation Method 1
light is incident on the surface of the semiconductor wafer to be evaluated, and the radiation light (scattered light and reflected light) from this surface is detected
Implementation Method 2
light is incident on the surface of the semiconductor wafer to be evaluated, and the radiation light (scattered light and reflected light) from this surface is detected
Implementation Method 3
an apparatus for calibration that obtains an X coordinate position and a Y coordinate position of the COP with a two-dimensional Cartesian coordinate system
Data Source
AI summary
The method includes detecting a COP in a surface of a reference wafer with a laser surface inspection apparatus to be calibrated and an apparatus for calibration that obtains an X coordinate position and a Y coordinate position of the COP; determining a COP that is detected as the same COP with a determination criterion that a positional difference between a detected position obtained by the laser surface inspection apparatus to be calibrated and a detected position obtained by the apparatus for calibration on the reference wafer surface is within a threshold range; and calibrating the coordinate position identification accuracy of the laser surface inspection apparatus to be calibrated by adopting the X and Y coordinate positions obtained by the apparatus for calibration as true values of the X and Y coordinate positions.