Wafer Coordinate Error Correction Using Pseudo Defects
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Optical type inspection apparatuses face challenges in accurately displaying and correcting defect coordinates, especially when dealing with fine defects, due to errors in coordinate measurement, leading to incomplete or inaccurate display of defects on the inspection screen.
Innovation Solution
The apparatus includes a line sensor with channels arrayed along the Y-axis, a stage position detecting unit, a coordinate transforming unit, and a difference computing unit, which form images of a wafer with pseudo defects to detect and correct position errors, allowing for precise coordinate transformation and error reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the review device displays with magnification only the periphery of the defect coordinate, then the display area is concentrated on a narrow region, but the defect may not be displayed if there is an error in the defect coordinate
Solution Approach 1:
The patent applies preliminary action by forming pseudo defects at known precise positions before actual inspection. These pseudo defects serve as reference markers that allow the system to pre-calculate and correct coordinate errors. By having known reference points in advance, the system can compensate for stage position deviations and ensure accurate defect localization even when coordinate errors occur during inspection.
Solution Approach 2:
The patent implements feedback by using the detected positions of pseudo defects to calculate coordinate error patterns, which are then applied to correct the coordinates of actual defects. The system continuously refines defect coordinate accuracy by comparing expected pseudo defect positions with actually detected positions, and using this feedback to adjust subsequent defect coordinate measurements.
2Measurement precision
If fine defects become the inspection target, then the inspection accuracy requirement increases, but the coordinate error becomes more significant relative to the defect size
Solution Approach 1:
The patent uses pseudo defects as intermediary reference objects between the stage positioning system and the actual fine defects. These intermediary markers, which are deliberately formed at precise known positions, serve as a bridge to calibrate and correct coordinate measurements. By measuring the positions of these intermediary pseudo defects and comparing them to their designed positions, the system can calculate and apply correction patterns to improve the precision of fine defect coordinate measurements.
3Measurement precision
If the stage position deviation is corrected using conventional methods, then the overall position accuracy improves, but the coordinate error pattern remains unknown and cannot be fully compensated
Solution Approach 1:
The patent applies self-service by using the pseudo defects themselves to generate the correction information needed. The system automatically detects pseudo defect positions, compares them to their designed positions, calculates the coordinate error patterns, and applies these corrections to defect coordinates. This self-calibrating mechanism eliminates the need for external calibration procedures and continuously maintains accurate coordinate information.
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 solution enables the optical type inspection apparatus to accurately reduce errors in defect coordinates, ensuring that even fine defects are properly displayed and analyzed, improving inspection accuracy and reliability.
Implementation Method 1
an optical type inspection apparatus including a line sensor with plural channels capable of forming an image of a surface of a wafer
Data Source
AI summary
This optical inspection device has: a line sensor on which channels are arranged; a moving means for moving a wafer mounted on a stage relative to the line sensor; a stage position detection means for detecting the on-stage positions of pseudo-defects in images formed on the channels as pseudo-defect stage coordinates, said coordinate management wafer being a wafer on which one pseudo-defect die is formed per row and column of a matrix of dies and each pseudo-defect die has a plurality of pseudo-defects formed in a line in the columnar direction; a coordinate transformation means for transforming the pseudo-defect stage coordinates into pseudo-defect die coordinates; a difference computation means for computing the differences of the pseudo-defect die coordinates from design coordinates; and a characteristic pattern acquisition means for obtaining a coordinate error characteristic pattern in which the differences from the pseudo-defect stage coordinates increase or decrease along a straight line.