Extreme-Ultraviolet Optical Inspection for Wafer Defects
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Solution Overview
Problem
The challenge in modern semiconductor manufacturing is the inspection of defects on wafers with diminishing feature sizes and intricate patterns, which requires finer resolution and shorter wavelength light, but this leads to weaker signal strength, lower inspection sensitivity, and increased complexity due to material variations and low material contrast.
Innovation Solution
An optical inspection system using an optical device with a light source generating a first laser beam with a wavelength less than 120 nm, which is directed through an illuminator to incident on a wafer, capturing a reflected laser beam through an objective to generate an image. The system includes an image processing device to generate a detection result based on the image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If shorter wavelength light is used to achieve finer resolution for smaller defects, then resolution is improved, but signal strength becomes weaker and inspection sensitivity decreases
Solution Approach 1:
The patent employs a wavelength converting channel that transforms pump laser light into extreme ultraviolet (EUV) light with wavelength less than 120 nm. This parameter change in wavelength enables the system to achieve the required resolution for sub-20nm defects while maintaining adequate signal strength through the wavelength conversion process, resolving the contradiction between resolution improvement and signal strength maintenance.
2Measurement precision
If shorter wavelength light is used to inspect smaller defects, then resolution is improved, but material contrast becomes lower and certain defects become undetectable
Solution Approach 1:
By changing the illumination wavelength to the extreme ultraviolet range through the wavelength converting channel, the system achieves enhanced material contrast for detecting sub-20nm defects. The EUV light interacts differently with various materials, providing sufficient contrast even for materials with similar properties, thus enabling detection of defects that would be invisible at longer wavelengths.
3Measurement precision
If inspection sensitivity is increased to detect smaller defects, then detection capability is improved, but throughput is decreased
Solution Approach 1:
The patent employs a laser-based inspection system with continuous scanning capability. The laser beam continuously scans the wafer surface, and the wavelength converting channel continuously generates EUV light during the inspection process. This continuous operation enables high inspection sensitivity for sub-20nm defect detection while maintaining high throughput by eliminating interruptions in the inspection process.
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
The system achieves high sensitivity and resolution for defect inspection on wafers, overcoming the challenges of weak signal strength and material variations, while maintaining efficient throughput.
Implementation Method 1
The light source is configured to generate a first laser beam and direct the first laser beam through an illuminator to be an incident laser beam toward a wafer
Implementation Method 2
so as to generate a reflected laser beam accordingly
Implementation Method 3
The image sensor is configured to capture the reflected laser beam through an objective to be a second laser beam and generate an image of the wafer accordingly
Data Source
AI summary
An optical inspection system includes an optical device and an image processing device. The optical device includes a light source and an image sensor. The light source is configured to generate a first laser beam and direct the first laser beam through an illuminator to be an incident laser beam toward a wafer, so as to generate a reflected laser beam accordingly. The image sensor is configured to capture the reflected laser beam through an objective to be a second laser beam and generate an image of the wafer accordingly. The image processing device is configured to generate a detection result according to the image. A wavelength of the incident laser beam is less than 120 nm.