Wafer Inspection Optics with Calibrated Diffraction Grating
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Solution Overview
Problem
Existing wafer inspection processes face challenges in achieving high wavelength resolution for inspecting highly scaled, high-density semiconductor chips, necessitating the development of apparatuses capable of generating monochromatic light with precise wavelengths.
Innovation Solution
A wafer inspection apparatus utilizing a diffraction grating with adjustable rotation angles and calibration parameters, calculated using a least squares method, to spectrally divide incident light into monochromatic beams, ensuring precise extraction of target wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a diffraction grating is used to spectrally divide incident light into monochromatic beams, then wavelength resolution is improved, but device complexity increases due to the need for precise grating rotation control and calibration
Solution Approach 1:
The patent changes the operational parameters of the diffraction grating by precisely controlling its rotation angle to select specific wavelengths. The grating equation λ = d(sinα + sinβ) is used to determine the relationship between grating rotation angle and output wavelength, allowing selective extraction of monochromatic beams by adjusting the grating's rotational parameter
Solution Approach 2:
The patent implements a feedback mechanism through wavelength calibration using known reference wavelengths. The system measures the actual wavelengths of monochromatic beams, compares them with reference values, and adjusts the grating rotation control to minimize wavelength errors, thereby improving measurement precision while managing system complexity
2Measurement precision
If calibration parameters are calculated using least squares method based on multiple wavelength measurements, then wavelength accuracy is improved, but measurement time and processing complexity increase
Solution Approach 1:
The patent performs wavelength calibration in advance using the least squares method to determine optimal grating rotation angles for specific wavelengths. By pre-calculating and storing the relationship between grating angles and wavelengths, the system avoids time-consuming real-time calculations during actual wafer inspection, thus reducing measurement time while maintaining high wavelength accuracy
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
Enhances the precision of wafer inspection by accurately extracting monochromatic light, improving the resolution and accuracy of semiconductor chip inspection.
Implementation Method 1
a diffraction grating configured to diffract the portion of the incident light and spectrally divide the portion of the incident light into monochromatic beams
Implementation Method 2
a first condensing mirror configured to focus the portion of the incident light that passes through the first slit; a second condensing mirror configured to focus the monochromatic beams
Data Source
AI summary
A wafer inspection apparatus is provided. The wafer inspection apparatus includes a light source generating incident light, an input part slit passing some of the incident light, an input part condensing mirror focusing incident light that passes through the input part slit, a diffraction grating diffracting the incident light and spectrally dividing the incident light into monochromatic beams, an output part condensing mirror focusing the monochromatic beams and an output part slit passing some of the monochromatic beams.