Wafer Inspection Using Nonlinear Scattering for Ultrafine Particles
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Solution Overview
Problem
Current wafer inspection methods struggle to detect ultrafine particles of 10 nm or less due to the Rayleigh diffraction limit, which limits the detection of defects in semiconductor devices as they become increasingly miniaturized.
Innovation Solution
A wafer inspection apparatus utilizing two input beams with different incident angles and wavelengths, employing nonlinear optical phenomena such as four-wave mixing to generate and detect nonlinear scattered light, which allows for the detection of ultrafine particles by isolating the signal from noise caused by surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the wavelength of input light is shortened to detect fine particles, then detection capability for fine particles is improved, but the Rayleigh diffraction limit is reached which prevents detection of ultrafine particles of 10 nm or less
Solution Approach 1:
The patent changes the fundamental parameter of light-matter interaction from linear optical scattering to nonlinear optical scattering. By using nonlinear optical phenomena (such as four-wave mixing) with multiple input beams, the detection mechanism transitions beyond the Rayleigh diffraction limit, enabling detection of ultrafine particles of 10 nm or less that cannot be detected by conventional linear optical methods
Solution Approach 2:
The patent employs a composite illumination approach using multiple laser beams with different wavelengths and incident angles simultaneously. This composite light field interacts with the ultrafine particles to generate nonlinear scattered light, combining the advantages of different wavelength regions to achieve enhanced detection capability beyond what any single wavelength could provide
2Device complexity
If conventional linear optical scattering is used for inspection, then the inspection process is simple, but the signal-to-noise ratio is low due to interference from surface roughness
Solution Approach 1:
The patent exploits the local quality difference between ultrafine particles and wafer surface roughness. By using nonlinear optical scattering with specific incident angle configurations, the system selectively enhances the scattering signal from particles while suppressing the scattering from surface roughness, as they exhibit different nonlinear optical responses at different incident angles
Solution Approach 2:
The patent implements continuous wafer inspection by maintaining constant nonlinear optical scattering detection during wafer processing. The system continuously irradiates the wafer with multiple laser beams and detects nonlinear scattered light in real-time, enabling ongoing monitoring of ultrafine particles throughout the manufacturing process without interrupting production
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 the detection of ultrafine particles and improves the signal-to-noise ratio, allowing for reliable inspection of non-patterned wafers with reduced noise interference, enhancing the detection of defects in semiconductor devices.
Implementation Method 1
employing nonlinear optical phenomena such as four-wave mixing to generate and detect nonlinear scattered light
Implementation Method 2
an objective lens on an optical path of the first and second input beams... the first input beam passing through the objective lens is obliquely incident on the wafer at a first incident angle... the second input beam passing through the objective lens is incident on the wafer at a second incident angle
Data Source
AI summary
A wafer inspection apparatus includes: an objective lens on an optical path of first and second input beams; and an image sensor configured to generate an image of the wafer based on scattered light according to a nonlinear optical phenomenon based on the first and second input beams, wherein the first input beam passing through the objective lens is obliquely incident on the wafer at a first incident angle with respect to a vertical line that is normal to an upper surface of the wafer, the second input beam passing through the objective lens is incident on the wafer at a second incident angle oblique to the vertical line that is normal to the upper surface of the wafer, and the first and second incident angles are different from each other.