Defect Inspection Device Using Polarized Light Transmission Control
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Solution Overview
Problem
Current defect inspection methods in semiconductor manufacturing struggle to accurately detect minute defects with high sensitivity and precision, as they fail to effectively separate scattered light from defects and the sample surface, leading to compromised signal-to-noise ratios and reduced detection sensitivity.
Innovation Solution
The implementation of a defect inspection device with a polarized light transmission control unit that adjusts transmission characteristics based on polarization characteristics, utilizing a birefringence phase difference control unit to create a phase difference between fast and slow phase axes, allowing selective transmission of light and enhancing the detection of scattered light from defects while reducing background noise from the sample surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If P-polarized light is used for illumination to maximize scattered light from minute defects, then defect detection sensitivity is improved, but scattered light from the sample surface is also maximized reducing signal-to-noise ratio
Solution Approach 1:
The invention changes the polarization state parameter of the illumination light from P-polarized to S-polarized light. This parameter change selectively suppresses scattered light from the sample surface while maintaining scattered light from defects, thereby improving signal-to-noise ratio without sacrificing defect detection sensitivity
Solution Approach 2:
The invention converts the harmful scattered light from the sample surface into a beneficial signal by using S-polarized illumination. The scattered light from the sample surface becomes suppressed while scattered light from defects remains detectable, transforming the noise problem into a signal enhancement opportunity
2Measurement precision
If linear polarizer and 1/4 wave plate are used to control polarized light rays, then inspection SNR is improved by detecting scattered light under orthogonal polarization conditions, but scattered light from defect and sample surface cannot be sufficiently separated when elliptically polarized light component is present
Solution Approach 1:
The invention changes the polarization parameter from using linear polarizer with 1/4 wave plate to using an S-polarized light source directly. This simplifies the polarization control system and reliably separates scattered light from defects and sample surface by utilizing the inherent polarization characteristics of S-polarized illumination
Solution Approach 2:
The invention extracts and removes the 1/4 wave plate from the polarization control system, keeping only the essential S-polarized light source. This extraction eliminates the problem of insufficient separation when elliptically polarized light is present, while maintaining the improved SNR benefit
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 results in high-speed and high-sensitivity defect detection by increasing the intensity of scattered light from defects relative to the sample surface, enabling more accurate and consistent measurement of defect position, type, and size.
Implementation Method 1
a birefringence phase difference control unit that causes a predetermined phase difference due to birefringence between a fast phase axis and a slow phase axis of the reflected light or scattered light
Implementation Method 2
a polarized light transmission unit that selectively transmits light according to a polarization direction of output light of the birefringence phase difference control unit
Implementation Method 3
detection optical system that collects reflected light or scattered light from the sample irradiated with the light
Data Source
AI summary
An inspection device includes an illumination optical system that irradiates a sample with light having a predetermined wavelength, a detection optical system that includes a photoelectric conversion unit, and a data processing unit that extracts positional information of a foreign substance or a defect on the sample. The light collection optical system includes a polarized light transmission control unit that changes transmission characteristics according to polarization characteristics of the collected reflected light or scattered light. The polarized light transmission control unit includes a birefringence phase difference control unit that causes a predetermined phase difference between a fast phase axis and a slow phase axis of the reflected light or scattered light according to the polarization characteristics of the reflected light or scattered light, and a polarized light transmission unit that selectively transmits light according to a polarization direction of output light of the birefringence phase difference control unit.