Dark-Field Microscope Polarization Filter for Defect Review
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Solution Overview
Problem
Existing methods for separating defect scattered light from roughness scattered light in semiconductor wafer inspection are inadequate, particularly for minute defects, as they either fail to completely block roughness scattered light or lack spatial correspondence between polarization direction images, leading to obscured defect detection.
Innovation Solution
A defect reviewing method and device utilizing a dark-field microscope and scanning electron microscope (SEM) with a control unit, where the dark-field microscope identifies defect positions using illumination light, a wavelength plate, and a filter to separate and distinguish defect scattered light from roughness scattered light, ensuring accurate positioning within the SEM's field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a filter is used to block roughness scattered light, then the intensity of roughness scattered light is reduced, but the defect scattered light may also be blocked and becomes undetectable
Solution Approach 1:
The patent segments the scattered light into multiple polarization directions and processes each direction separately. By dividing the light into orthogonal polarization components, the system can selectively block roughness scattered light in certain polarization directions while preserving defect scattered light in other polarization directions, thus resolving the contradiction between blocking roughness light and maintaining defect detection capability.
Solution Approach 2:
The patent changes the polarization parameter of the scattered light by using a polarization beam splitter to separate light into different polarization directions. This parameter change allows the system to differentiate between roughness scattered light and defect scattered light based on their different polarization characteristics, enabling selective filtering without losing defect signals.
2Measurement precision
If multiple detectors are used to separately capture images in various polarization directions, then scattered light intensity comparison is possible, but spatial correspondence between images is lost
Solution Approach 1:
The patent merges multiple polarization direction images into a single composite image that preserves spatial correspondence. By combining the intensity information from different polarization directions at each pixel location, the system maintains the spatial relationship between defects and the wafer surface while still enabling intensity comparison across polarization directions.
3Illumination intensity
If high-intensity illumination is used to increase storage time, then the intensity of defect scattered light increases, but roughness scattered light also increases and obscures the defect
Solution Approach 1:
The patent segments the scattered light into multiple polarization directions, allowing the system to accumulate signal intensity in directions where defect scattered light dominates while suppressing directions where roughness scattered light dominates. This segmentation enables effective signal accumulation without proportionally increasing roughness interference.
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 effectively distinguishes and positions minute defects within the SEM's field of view, enhancing the ability to review detailed defect information by reducing interference from roughness scattered light.
Implementation Method 1
The wavelength plate converts the polarization directions of the scattered light from the sample, which is collected by the objective lens
Implementation Method 2
The filter blocks part of the scattered light transmitted through the wavelength plate and transmits the remaining portion of the scattered light
Implementation Method 3
Scattering from an object having a wavelength sufficiently smaller than an illumination wavelength is Rayleigh scattering
Implementation Method 4
Scattering from an object having a wavelength sufficiently smaller than an illumination wavelength is Rayleigh scattering, which is proportional to the sixth power of the particle diameter of a scatterer
Implementation Method 5
The imaging lens forms an image of the scattered light transmitted through the filter
Data Source
AI summary
To review minute defects that were buried in roughness scattered light with an observation device provided with a dark-field microscope, a scanning electron microscope (SEM), and a control unit, the present invention configures the dark-field microscope by installing a filter for blocking a portion of the scattered light, an imaging lens for focusing the scattered light that has passed through the filter, and a detector for dividing the image of the scattered light focused by the imaging lens into the polarization directions converted by a wavelength plate and detecting the resulting images, and the control has a calculation unit for determining the position of a defect candidate detected by another inspection device using the plurality of images separated into polarization directions and detected by the detector.