Hole Depth Measurement via Dual-Spectrum Difference Area
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Solution Overview
Problem
Existing methods for monitoring the depth of small holes and film thickness during etching and film growth processes are prone to noise interference, lack precision, and cannot accommodate rapid changes, making it difficult to accurately measure dimensions in real-time.
Innovation Solution
A surface treatment status monitoring device that uses a light source with a predetermined wavelength bandwidth, an interference optical system, and a spectrometric unit to acquire and analyze interference spectra at two time points, calculating the absolute difference area to determine dimensional changes, thereby enhancing measurement robustness against noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If spectral fitting analysis is used to measure hole depth or film thickness, then measurement capability is provided, but measurement precision deteriorates due to noise interference and inability to accommodate rapid changes
Solution Approach 1:
The patent segments the interference spectrum into multiple wavelength regions and processes each region separately to calculate local slope values. This segmentation allows the system to capture rapid local changes in the spectrum while reducing the impact of noise on overall measurement accuracy. By dividing the spectrum analysis into manageable segments, the method achieves both precision and reliability in measuring hole depth or film thickness during rapid processes.
2Speed
If conventional spectrometric measurement with spectral fitting is used, then dimensional measurement capability is achieved, but the system cannot accommodate rapid changes in etching or film growth processes
Solution Approach 1:
The patent implements a dynamic measurement approach by continuously calculating the slope of the interference spectrum at different wavelength points and using these slope variations to determine dimensional changes. This dynamic method can accommodate rapid changes in etching or film growth processes because it responds to instantaneous spectral changes rather than relying on static spectral fitting. The system updates measurements in real-time as the process evolves, maintaining precision even during fast process transitions.
3Measurement precision
If spectral fitting methods are used to analyze interference fringes, then hole depth measurement is enabled, but noise interference reduces measurement accuracy
Solution Approach 1:
The patent extracts the useful measurement information by focusing on the slope of the interference spectrum rather than attempting to fit the entire spectrum. By taking out and analyzing only the slope component at different wavelength points, the method isolates the signal containing dimensional information from the noise. This extraction approach eliminates the need for complex spectral fitting that is susceptible to noise, thereby improving measurement precision while reducing the impact of noise interference.
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 device achieves high signal-to-noise ratio measurements by integrating wavelength direction information, allowing for precise monitoring of dimensional changes, even during rapid processes, and effectively suppresses noise, enabling accurate detection of etching depth and film thickness.
Implementation Method 1
an interference optical system which generates interference of light reflected respectively from a first plane and a second plane of the structure to be measured
Implementation Method 2
a spectrometric unit which disperses wavelength of the interference light generated by the interference optical system
Data Source
AI summary
A measurement light having a predetermined wavelength bandwidth from a light source is radiated onto the structure to be measured in a specimen 50, light reflected from a first plane and second plane of the structure to be measured is made to interfere in an optical fiber, and a spectrum of the interference light is generated. This interference light spectrum is acquired by a spectrometric unit at two time points separated in time, and in data processing unit, absolute difference area computation unit determines the absolute difference area of the difference spectrum. This absolute difference area changes periodically each time the dimension of the structure to be measured changes by λ/4, making it possible to determine the dimension of the structure to be measured based on that change.