Multi-Wavelength Light Emission for Surface Topography Measurement
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Solution Overview
Problem
Existing techniques for measuring surface topography and stress in thin films on semiconductor wafer substrates face challenges due to destructive interference and noise interference, leading to inaccurate curvature measurements and inefficiencies in detecting reflected beams.
Innovation Solution
An apparatus and method utilizing a light emitting assembly that emits beams at multiple wavelengths modulated with different frequencies, combined into a single beam to reduce destructive interference and noise, allowing for accurate determination of surface topography and stress by using a position-sensitive detector and signal processing unit to generate and process signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single wavelength beam is used for measurement, then the device complexity is low, but destructive interference occurs leading to measurement inaccuracies
Solution Approach 1:
The patent combines multiple light beams of different wavelengths into a single composite beam for measurement. This merging approach allows the system to benefit from multiple wavelengths (reducing destructive interference) while maintaining a relatively simple single-beam emission structure, thus resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The patent uses a composite light beam consisting of multiple wavelengths combined together. This composite approach enables the measurement system to avoid the destructive interference problems of single-wavelength beams while not requiring completely separate emission systems for each wavelength, balancing precision improvement with device simplicity
2Measurement precision
If multiple wavelengths are used without modulation, then measurement information is more comprehensive, but noise interference increases reducing signal quality
Solution Approach 1:
The patent applies periodic modulation to each wavelength component at distinct frequencies. This periodic action allows the detector to distinguish between different wavelength components and their corresponding reflected signals through frequency analysis, thereby maintaining comprehensive measurement information while effectively separating and reducing noise interference
Solution Approach 2:
The patent introduces dynamic frequency modulation to differentiate between multiple wavelength components. By assigning different modulation frequencies to different wavelengths, the system dynamically separates the signals in the frequency domain, allowing comprehensive multi-wavelength measurement while maintaining high signal-to-noise ratio through frequency-based signal processing
3Productivity
If multiple light beams are measured simultaneously without frequency differentiation, then productivity is high, but signal detection becomes unreliable due to interference
Solution Approach 1:
The patent uses periodic modulation at distinct frequencies for each simultaneously measured beam. This allows all beams to be measured in parallel (maintaining high productivity) while the frequency differentiation enables reliable signal detection and separation through spectral analysis, preventing interference between simultaneous measurements
Solution Approach 2:
The patent introduces frequency modulation as an intermediary mechanism that enables simultaneous measurement of multiple beams. The distinct modulation frequencies act as identifiers that allow the detection system to separate and accurately detect each beam's reflected signal, thus maintaining both high productivity and reliable detection
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 beam quality, reduces noise, and enables simultaneous measurement of multiple light beams, improving the accuracy and efficiency of surface topography and stress measurement, thereby addressing the limitations of existing methods.
Implementation Method 1
a light emitting assembly configured to emit an emitted beam of light. The emitted beam is emitted at a plurality of wavelengths and is modulated with a modulating frequency
Implementation Method 2
a detector configured to receive a reflected beam of light that includes at least a portion of the emitted beam as reflected from the surface of the work-piece and generate a signal indicative of a position of the reflected beam on the detector
Implementation Method 3
a signal processing unit configured to remove noise from the signal thus generated based on the modulating frequency to obtain a processed signal
Implementation Method 4
The emitted beam is directed onto a surface of a work-piece... determine the topography of the surface based on the processed signal
Data Source
AI summary
An apparatus and a method for measuring surface topography of a work-piece are described. The apparatus comprises a light emitting assembly configured to emit an emitted beam of light, the emitted beam being emitted at a plurality of wavelengths and modulated at modulating frequency, the emitted beam being directed onto a surface of a work-piece. A detector is configured to receive a reflected beam of light that includes at least a portion of the emitted beam as reflected from the surface of the work-piece. The detector is further configured to generate a signal indicative of a position of the reflected beam on the detector. A signal processing unit is configured to remove noise from the signal thus generated based on the modulating frequency to obtain a processed signal. A control unit is configured to determine topography of the surface based on the processed signal.