Optical Test System for Semiconductor Defect Detection
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Solution Overview
Problem
Existing methods for defect detection on semiconductor wafers or devices struggle to distinguish defects of certain sizes due to surface roughness, making it difficult to differentiate between defects and noise.
Innovation Solution
An optical test system that employs multiple incident optical systems positioned at non-right angles to change the polarization state of light beams, allowing for the detection of reflected light beams at unique reflection angles, enabling the generation of image data that differentiates between defects and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light beams are incident at right angles for defect detection, then the detection process is simple, but defects of certain sizes cannot be distinguished from noise due to surface roughness
Solution Approach 1:
The optical test system is divided into multiple incident optical systems (first incident optical system, second incident optical system, etc.), each illuminating the test region from different directions. This segmentation allows the system to capture reflected light from multiple angles, enabling distinction between defects and surface roughness noise that cannot be achieved with a single right-angle incident beam.
Solution Approach 2:
The patent transitions from single-dimension (right-angle) incident light to multi-dimension incident light by introducing light beams at different incident angles and directions. This dimensional expansion of the optical illumination approach enables the detection system to differentiate defects from surface roughness by analyzing reflected light patterns from multiple spatial perspectives.
2Measurement precision
If multiple incident optical systems are used to detect defects at different angles, then defect detection precision is improved, but the device complexity increases
Solution Approach 1:
Each incident optical system is designed with polarization state changing capabilities, allowing a single optical system to perform multiple functions: illuminating the test region, controlling polarization states, and detecting reflected light. This multi-functionality reduces the need for separate specialized components for each function, thereby managing device complexity while maintaining high detection precision through multi-angle illumination.
3Measurement precision
If polarization state changing is applied to light beams, then the ability to distinguish defects from noise is improved, but the complexity of the optical system increases
Solution Approach 1:
The patent changes the polarization state parameter of incident light beams using polarization state changing units in each incident optical system. By controlling and varying polarization states (e.g., s-polarization, p-polarization, elliptical polarization) and analyzing changes in reflected light polarization, the system enhances the contrast between defects and surface roughness, improving signal-to-noise ratio while managing optical component complexity through systematic polarization control.
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 detects defects, even at a nano-sized level, by processing image data from light beams incident at various angles, improving accuracy and distinguishing surface roughness from actual defects.
Implementation Method 1
a first incident optical system to change a first polarization state of a first light beam to a second polarization state and to provide the first light beam in the second polarization state to the stage region
Implementation Method 2
a main optical system to detect a first reflected light beam reflected at a first reflection angle different from the first and second incident angles among a plurality of reflected light beams obtained after the first light beam in the second polarization state is reflected from the stage region
Data Source
AI summary
An optical test system includes a stage region to accommodate an object to be tested, a first incident optical system which changes a first polarization state of a first light beam to a second polarization state and provide the first light beam in the second polarization state to the stage region in a first direction at a first incident angle which is not a right angle, a second incident optical system which changes a third polarization state of a second light beam to a fourth polarization state and inputs the second light beam in the fourth polarization state to the stage region in a second direction at a second incident angle which is not a right angle, and a main optical system to detect a first reflected light beam reflected from the stage region at a first reflection angle different from the first and second incident.