Defect Inspection Device Dot Pattern Chip Focal Adjustment
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Solution Overview
Problem
Existing defect inspection devices face challenges in precisely adjusting the focal position of illumination and detection optical systems due to the spread of images caused by defocus and changes in peak strength, especially when dealing with oblique patterns and linear illumination, leading to instability in defect detection.
Innovation Solution
The implementation of a defect inspection device with a pattern chip featuring a dot pattern area where the minimum interval between dots is smaller than the illumination light width and larger than the detection optical system's resolution, allowing for precise adjustment of the optical system by detecting scattered light patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a line and space pattern orthogonal to the illumination beam is used, then the pattern can be clearly detected, but the image spread due to defocus reduces measurement precision for focal position adjustment
Solution Approach 1:
The patent applies asymmetry by using a line and space pattern that is NOT orthogonal to the illumination beam direction. Specifically, the pattern is arranged at an angle such that the lines are inclined relative to the illumination beam, creating an asymmetric relationship between the illumination direction and the pattern orientation. This asymmetric arrangement causes the image of the line pattern to spread in a specific direction when defocused, making the defocus amount easily detectable through image spread measurement, thereby enabling precise focal position adjustment.
2Measurement precision
If linear illumination light with finite width is used, then the illumination area is well-defined, but the overlapping area with the pattern creates image spread that reduces focal position detection accuracy
Solution Approach 1:
The patent applies parameter changes by carefully selecting the pitch (spacing) of the line and space pattern relative to the width of the illumination beam. The pattern pitch is designed to be smaller than the illumination beam width, creating a specific geometric relationship. This parameter relationship ensures that when the pattern is illuminated, the resulting image has characteristics that are highly sensitive to defocus changes, allowing precise focal position detection through image spread measurement while maintaining sufficient image 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 configuration enables high-precision adjustment of the optical system, resulting in stable and sensitive defect inspection capabilities by ensuring accurate alignment and focus across the detection area.
Implementation Method 1
detects a scattered light generated from a surface of a sample or a surface of a pattern chip by the illumination light
Data Source
AI summary
In a defect inspection device that irradiates a surface of a sample or a surface of a pattern chip with an illumination light shaped to extend in a first direction, and detects a scattered light generated from the surface of the sample or the surface of the pattern chip by the illumination light to detect a defect on the surface of the sample, the pattern chip has a dot pattern area in which multiple dots are arrayed in multiple rows and multiple columns, a minimum interval between the dots corresponding to the lines aligned in the first direction among the multiple dots arrayed in the dot pattern area in a second direction orthogonal to the first direction is smaller than a width of the illumination light, and a minimum interval between the multiple dots arrayed in the dot pattern area is larger than a resolution of the detection optical system.