Broadband Light Source for Semiconductor Wafer Defect Inspection
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Solution Overview
Problem
The sensitivity of defect detection in semiconductor wafer inspections is reduced due to changes in reflection intensity caused by intramembranous multiple interference on oxide films and increased background light noise from surface roughness of metal films, which complicates the detection of finer defects.
Innovation Solution
A defect inspection method using a high-coherent broadband light source that selects a specific wavelength and forms the light beam in a shape long in one direction for oblique irradiation on the inspection target, combined with a spatial filter to block scattered light from patterns, improving image capture and processing to extract defects effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser light sources are used for illumination in defect inspection, then inspection speed is maintained at high levels, but interference from oxide films and surface roughness increases background noise and reduces detection sensitivity
Solution Approach 1:
The patent changes the illumination parameter from single-wavelength laser light to broadband light with specific wavelength characteristics. By using broadband light and selecting specific wavelengths through a wavelength selecting element, the system reduces interference from oxide films and surface roughness while maintaining high inspection speed through the high brightness of the broadband light source.
2Measurement precision
If broadband light sources are used to reduce interference, then detection sensitivity improves, but inspection speed decreases and system complexity increases
Solution Approach 1:
The patent makes the broadband light source serve multiple functions: it provides high brightness illumination for fast inspection while simultaneously enabling wavelength selection to reduce interference. The wavelength selecting element allows the same broadband source to operate at different wavelength bands, making it adaptable for various inspection conditions without requiring multiple separate light sources.
3Measurement precision
If multiple light sources are used to address different interference issues, then detection quality improves, but device complexity increases
Solution Approach 1:
The patent consolidates multiple light source functions into a single broadband light source with wavelength selection capability. Instead of using separate laser sources for different wavelength bands, the system uses one broadband source that can select specific wavelengths as needed, reducing optical system complexity while maintaining detection quality.
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 detection sensitivity by reducing interference from oxide films and surface roughness, maintaining inspection speed comparable to laser illumination systems while simplifying the optical system.
Implementation Method 1
a high-coherent broadband light source that selects a specific wavelength and forms the light beam
Implementation Method 2
combined with a spatial filter to block scattered light from patterns
Implementation Method 3
forms the light beam in a shape long in one direction for oblique irradiation on the inspection target
Data Source
AI summary
In inspecting a substrate having a transparent oxide film or a metal film formed on a surface thereof by using a dark field type inspection apparatus installing a laser light source, an illuminating beam having a high coherence causes variations in reflection strength due to multiple interferences within the transparent oxide film or an interference of scattered beams due to the surface roughness of the metal film occurs and which leads to degradation in the sensitivity of defect detection. The present invention solves the problem by providing a low-coherence but high-brightness illumination using a highly directive broadband light source, and a system in which the conventional laser light source is simultaneously employed to selectively use the light sources, thereby enabling a highly sensitive inspection according to the condition of a wafer.