Polarization Control for Semiconductor Defect Inspection
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Solution Overview
Problem
Current inspection methods struggle to accurately distinguish between defects that affect semiconductor pattern quality, such as short-circuit and open-circuit defects, and edge roughness, especially when these defects are below the resolution limit of optical systems, leading to throughput degradation and inefficient defect detection.
Innovation Solution
An inspection method and apparatus that utilize linearly-polarized light and polarization control elements, including a half-wave plate and analyzer, to optimize the polarization state of illumination light, allowing for the differentiation between defects by minimizing the impact of edge roughness and enhancing the visibility of critical defects through controlled polarization adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical inspection methods are used to detect fine patterns below the resolution limit, then the inspection can be performed with existing equipment, but the ability to distinguish between critical defects (short-circuit, open-circuit) and non-critical defects (edge roughness) is lost
Solution Approach 1:
The patent changes the polarization state parameter of the illumination light by using a half-wave plate to rotate the polarization direction. This parameter change enables the optical system to differentiate between critical defects (short-circuit, open-circuit) and non-critical defects (edge roughness) even when they are below the resolution limit, thereby improving measurement precision while preserving defect type information.
Solution Approach 2:
The patent applies different polarization states to different defect types by adjusting the half-wave plate angle. Critical defects exhibit different optical responses compared to non-critical defects under polarized illumination, allowing local differentiation of defect quality and type based on their unique optical characteristics.
2Measurement precision
If the resolution of the optical system is increased to detect finer defects, then the detection capability is improved, but the complexity and cost of the inspection apparatus increases
Solution Approach 1:
Instead of increasing the physical resolution of the optical system, the patent changes the polarization state parameter of the illumination light. This approach enables the detection and differentiation of fine defects below the conventional resolution limit without requiring more complex optical components or higher numerical aperture lenses.
Solution Approach 2:
The patent replaces the need for high-resolution mechanical/optical systems with an optical field manipulation approach using polarization control. By using a half-wave plate and analyzer to manipulate the polarization state, the system achieves enhanced defect detection capability without increasing mechanical or optical system complexity.
3Measurement precision
If multiple inspection parameters are analyzed to distinguish defect types, then the accuracy of defect classification is improved, but the inspection time and throughput are reduced
Solution Approach 1:
The patent uses polarization state as a single powerful parameter that encodes multiple defect characteristics. By analyzing the intensity distribution changes when the half-wave plate angle is varied, the system can classify defect types (short-circuit, open-circuit, edge roughness) accurately while maintaining high throughput, as the polarization parameter provides rich information in a single measurement dimension.
Solution Approach 2:
The patent employs periodic variation of the half-wave plate angle to systematically probe different polarization states. This periodic action allows the extraction of multiple defect characteristics through a structured sequence of measurements, improving classification accuracy while keeping the inspection process efficient and time-controlled.
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 accurate detection of short-circuit and open-circuit defects while minimizing the influence of edge roughness, thereby improving defect detection sensitivity and maintaining high throughput without the limitations of optical resolution constraints.
Implementation Method 1
transmitting the linearly-polarized light through a half-wave plate
Implementation Method 2
reflecting the linearly-polarized light emitted from a light source through a half-wave plate using an non-polarizing beam splitter
Implementation Method 3
the light reflected by the sample to be incident to an image capturing sensor through a lens, the non-polarizing beam splitter, and an analyzer
Data Source
AI summary
An inspection method and apparatus comprising, a step of reflecting linearly-polarized light having a predetermined wavelength using an non-polarizing beam splitter after transmitting the linearly-polarized light through a half-wave plate, irradiating a sample with the linearly-polarized light having a polarization plane of a predetermined angle, causing the light reflected by the sample to be incident to an image capturing sensor through a lens, the non-polarizing beam splitter, and an analyzer, and acquiring an optical image of a pattern formed on the sample; acquiring a plurality of optical images by changing an angle of the analyzer or the half-wave plate, and obtaining an angle of the analyzer or the half-wave plate such that a value of (σ/√A) becomes a minimum; and a step of inspecting whether a defect of the pattern exists, wherein the pattern is a repetitive pattern having a period at a resolution limit or less.