Polarization Beam Splitter for Parallel Defect Inspection
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Solution Overview
Problem
Conventional optical defect inspection methods for semiconductor wafers face challenges in efficiently utilizing polarization characteristics, leading to reduced detection sensitivity and increased detection time due to the need for multiple measurements under different polarization conditions.
Innovation Solution
The method involves modulating multiple states of polarization in the lighting beam and simultaneously imaging scattered light on a sensor with pixels configured to detect different polarization conditions, allowing for multiple measurements without increasing detection time by applying light with different polarizations within a single illumination and detecting these states efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple measurements are performed under different polarization conditions to improve defect detection sensitivity, then detection accuracy is improved, but detection time increases
Solution Approach 1:
The patent combines multiple polarization measurements into a single illumination process by using a polarization beam splitter to direct different polarization states to separate detectors simultaneously. This allows multiple measurements under different polarization conditions to be performed in parallel rather than sequentially, improving defect detection sensitivity while maintaining throughput.
Solution Approach 2:
The patent introduces a spatial dimension by using a polarization beam splitter to separate polarization states into different spatial paths. This allows multiple polarization measurements to occur simultaneously in different spatial directions, converting a time-consuming sequential process into a parallel spatial process that improves detection speed without sacrificing accuracy.
2Measurement precision
If multiple polarization measurements are performed sequentially to obtain comprehensive defect information, then inspection accuracy is improved, but productivity decreases
Solution Approach 1:
The patent merges multiple sequential polarization measurements into a single parallel measurement process. By using a polarization beam splitter to direct different polarization states to separate detectors simultaneously, the system obtains comprehensive defect information across multiple polarization conditions in one inspection cycle, thereby improving accuracy while maintaining high throughput.
Solution Approach 2:
The patent transitions from temporal multiplexing (sequential measurements) to spatial multiplexing (parallel measurements). By separating polarization states into different spatial paths using a polarization beam splitter, the system enables simultaneous acquisition of multiple polarization components, effectively increasing productivity without compromising inspection accuracy.
3Device complexity
If conventional single-detector schemes are used, then device complexity is low, but detection sensitivity varies depending on defect types
Solution Approach 1:
The patent segments the detection function by using multiple detectors, each specialized for detecting specific polarization components. This segmentation allows each detector to be optimized for its specific polarization detection task, improving overall defect detection sensitivity across different defect types while maintaining manageable system complexity through modular detector configuration.
Solution Approach 2:
The patent creates a multi-functional detection system where multiple detectors work together to cover various polarization states and defect types. This universal approach allows a single inspection system to handle diverse defect characteristics effectively, improving detection sensitivity without requiring separate specialized systems for each defect type.
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 enhances defect inspection sensitivity and sorting performance while maintaining throughput, enabling effective detection and classification of defects on semiconductor wafers with improved accuracy.
Implementation Method 1
modulating multiple states of polarization in the lighting beam and simultaneously imaging scattered light on a sensor
Implementation Method 2
reflected, diffracted, and scattered light from these defects and foreign substances are really weak
Implementation Method 3
these images are used to improve defect detection sensitivity
Data Source
AI summary
To effectively utilize the polarization property of an inspection subject for obtaining higher inspection sensitivity, for the polarization of lighting, it is necessary to observe differences in the reflection, diffraction, and scattered light from the inspection subject because of polarization by applying light having the same elevation angle and wavelength in the same direction but different polarization. According to conventional techniques, a plurality of measurements by changing polarizations is required to cause a prolonged inspection time period that is an important specification of inspection apparatuses. In this invention, a plurality of polarization states are modulated in micro areas in the lighting beam cross section, images under a plurality of polarized lighting conditions are collectively acquired by separately and simultaneously forming the scattered light from the individual micro areas in the individual pixels of a sensor, whereby inspection sensitivity and sorting and sizing accuracy are improved without reducing throughput.