Optical Metrology System for High-Speed Spectral Imaging
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Solution Overview
Problem
Conventional point-by-point inspection methods for photoluminescence and reflectance measurements on semiconductor wafers are slow and impractical for large specimen sizes, limiting throughput in quality inspection applications.
Innovation Solution
An optical metrology device capable of simultaneous detection of photoluminescence, specular reflection, and scattered light across a line on a sample, using a first light source to produce an illumination line and a broadband light source to overlay and reflect light, with a detector and processor to analyze the signals for multiple positions on the sample surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If point-by-point inspection method is used, then measurement precision can be achieved, but measurement speed and throughput deteriorate
Solution Approach 1:
The patent segments the measurement process by dividing the wafer surface into multiple measurement lines that can be simultaneously acquired. Instead of measuring one point at a time, the system uses a line scanner to capture multiple points along a line concurrently, then stitches multiple lines together to form a complete wafer map, thereby increasing throughput while maintaining precision.
Solution Approach 2:
The patent transitions from one-dimensional point-by-point scanning to two-dimensional line scanning. By illuminating and detecting along an entire line simultaneously rather than scanning points sequentially, the system adds a spatial dimension to the measurement process, achieving both high precision and high throughput.
2Measurement precision
If point-by-point inspection method is used, then detailed spectral analysis can be performed, but measurement time increases
Solution Approach 1:
The patent segments the spectral measurement across multiple wavelengths simultaneously using a spectrograph. Each wavelength component is detected in parallel along the measurement line, allowing detailed spectral analysis without requiring sequential scanning at each wavelength, thus reducing measurement time while preserving spectral resolution.
Solution Approach 2:
The system performs continuous spectral measurement across all wavelengths simultaneously along the illumination line. The spectrograph continuously disperses and detects all spectral components in parallel, eliminating the need for sequential wavelength scanning and maintaining continuous useful action throughout the measurement process.
3Device complexity
If single illumination source is used, then device complexity is reduced, but measurement versatility deteriorates
Solution Approach 1:
The patent employs a dual illumination source system where a first light source (e.g., laser) provides coherent illumination for high-precision spectral measurements, while a second light source (e.g., broadband source) provides incoherent illumination for reflectance and scattering measurements. This multi-functional illumination system enables the same optical platform to perform multiple measurement types without requiring separate dedicated systems.
Solution Approach 2:
The patent merges two different illumination sources and their respective measurement capabilities into a single integrated optical system. Both light sources share common optical components such as the spectrograph and detector, allowing simultaneous or sequential acquisition of photoluminescence and reflectance data from the same sample location, thereby increasing versatility without proportionally increasing complexity.
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 high-resolution, high-speed measurement of photoluminescence and reflectance across the entire sample surface, significantly improving measurement throughput and efficiency compared to traditional methods.
Implementation Method 1
a first light source that produces a first illumination beam; an optical system that receives the first illumination beam and produces an illumination spot on a surface of the sample; wherein the sample emits photoluminescence light in response to excitation caused by the illumination spot
Implementation Method 2
a broadband light source that produces broadband light; a lens that focuses the broadband light into a second illumination line on the surface of the sample... wherein the second illumination line is reflected by the sample to produce reflected light
Data Source
AI summary
An optical metrology device is capable of detection of any combination of photoluminescence light, specular reflection of broadband light, and scattered light from a line across the width of a sample. The metrology device includes a first light source that produces a first illumination line on the sample. A scanning system may be used to scan an illumination spot across the sample to form the illumination line. A detector collects the photoluminescence light emitted along the illumination line. Additionally, a broadband illumination source may be used to produce a second illumination line on the sample, where the detector collects the broadband illumination reflected along the second illumination line. A signal collecting optic may collect the photoluminescence light and broadband light and focus it into a line, which is received by an optical conduit. The output end of the optical conduit has a shape that matches the entrance of the detector.