Dark Field Microscope Spatial Filter for Semiconductor Defect Inspection
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Solution Overview
Problem
High Numerical Aperture (NA) optical systems in defect inspection for semiconductor wafers suffer from an elongating phenomenon, where dark field images of defects are streaked, leading to reduced accuracy in defect position determination and altered defect shape perception.
Innovation Solution
A defect detection method and device that irradiates the sample with light at an oblique direction, uses an objective lens with a filter to shield scattered light near the outer edge, and processes images to suppress the elongating phenomenon, allowing for accurate defect position calculation based on luminance signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high NA optical system is used for defect detection, then detection sensitivity is improved, but elongating phenomenon occurs causing reduced measurement precision
Solution Approach 1:
The patent extracts and removes the harmful scattered light components that cause the elongating phenomenon by using a spatial filter to block light in specific angular ranges, thereby eliminating the cause of image distortion while preserving the useful scattered light for defect detection
Solution Approach 2:
The patent applies different quality characteristics to different regions of the optical system by using a spatial filter with non-uniform transmission characteristics, allowing the center region to pass useful scattered light while blocking the outer regions that produce harmful elongation
2Productivity
If high NA objective lens is used, then more scattered light is captured improving detection sensitivity, but dark field images become streaked reducing position accuracy
Solution Approach 1:
The spatial filter acts as an intermediary element between the objective lens and the image plane, selectively mediating which scattered light components reach the detector. It allows useful scattered light to pass while blocking the components that cause elongation, thus resolving the contradiction between sensitivity and precision
3Measurement precision
If scattered light from outer edge region is blocked, then elongating phenomenon is suppressed improving position accuracy, but detection sensitivity may be reduced
Solution Approach 1:
The patent changes the angular distribution parameter of the scattered light by using a spatial filter with specific transmission characteristics. This modifies the light distribution in the image plane, suppressing elongation while maintaining sufficient scattered light intensity for defect detection
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
Enables high-accuracy detection of minute defects on semiconductor wafers by preventing the elongating phenomenon, improving positional accuracy and throughput in defect inspection.
Implementation Method 1
condensing a scattered light scattered light generated from the sample irradiated with the light
Implementation Method 2
condensing a scattered light scattered light generated from the sample irradiated with the light and incident on an objective lens to focus an image of the scattered light
Implementation Method 3
partially shielding a component of the scattered light transmitting a region near to an outer edge portion of an aperture of the objective lens in the scattered light
Data Source
AI summary
The present invention is suppressing the elongating phenomenon in the dark field image of defects in detecting a minute defect by using a dark field microscope. Provided is a method for detecting defects in which scattered light generated from the sample, is concentrated to form an image and is captured and processed to extract a defect to find the positional information of the defect, and the positional information is output, wherein an image of the scattered light that suppresses the occurrence of the elongating phenomenon is formed for which partial shielding of a component of the forward scattered light, that passes through a region near the outer edge of the field of view of the objective lens, and the positional information for the defect is found from a luminance signal for a defect that is extracted from a captured scattered light image that suppresses the occurrence of the elongating phenomenon.