Endpoint Detection in Semiconductor Etching Using Fourier Transform
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Solution Overview
Problem
Existing methods for detecting the endpoint of etching in semiconductor devices, such as plasma monitoring and optical interference, have limitations, including the need for specific elements or interference patterns, which can restrict the precision and accuracy of semiconductor layer etching, particularly for stacked semiconductor layers like those in vertical cavity surface-emitting lasers.
Innovation Solution
A method involving optical monitoring of reflected light from the etched surface, conversion to an electric signal, and subsequent Fourier transform to generate a spectrum signal for determining the endpoint of etching, allowing precise detection without relying on specific elements or interference patterns, and enabling control of etching rates between device and accessory areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If plasma monitoring method is used for endpoint detection, then etching process can be monitored, but the semiconductor layer must contain detectable elements which limits applicability
Solution Approach 1:
The patent replaces plasma monitoring (which relies on detecting specific elements in plasma) with optical interference monitoring. The optical method uses reflected light interference patterns to detect the etching endpoint, eliminating the need for specific detectable elements in the semiconductor layer. This substitution makes the endpoint detection universally applicable to all semiconductor layer types while maintaining high precision through interference pattern analysis.
2Measurement precision
If optical interference method is used for endpoint detection, then endpoint can be detected through reflected light, but requires specific interference patterns which limits flexibility
Solution Approach 1:
The patent enhances the optical interference method by introducing Fourier transform analysis of the reflected light spectra. Instead of relying solely on visual interference patterns, the system converts optical signals into spectral data and uses Fourier transform to identify characteristic frequencies corresponding to different layer depths. This dimensional transformation from spatial interference patterns to frequency domain analysis provides more flexible and accurate endpoint detection for various semiconductor structures.
3Productivity
If conventional endpoint detection methods are used, then etching can be monitored, but manufacturing precision of semiconductor layer thickness is affected
Solution Approach 1:
The patent implements real-time feedback control by continuously monitoring the optical interference patterns during etching and using Fourier transform analysis to detect the endpoint. The system provides immediate feedback on the etching progress by analyzing changes in the spectral frequencies, allowing precise control of the etching process to achieve the desired layer thickness while maintaining high productivity through automated real-time monitoring.
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 enables accurate and precise endpoint detection during semiconductor etching, ensuring stable semiconductor device characteristics by determining the endpoint based on changes in the spectrum signal, allowing for controlled etching and minimizing overetching, thereby achieving consistent and reproducible semiconductor layer thicknesses.
Implementation Method 1
optically monitoring an optical signal including a light component reflected from an etched surface of the substrate product
Implementation Method 2
performing Fourier transform on the monitoring signal to generate a spectrum signal
Data Source
AI summary
A method for producing a semiconductor device includes the steps of: providing a substrate product including a substrate and a first stacked semiconductor layer disposed on the substrate, the first stacked semiconductor layer including a plurality of semiconductor layers having different compositions that are alternately and periodically stacked with a predetermined period; forming a mask on the substrate product; and etching the first stacked semiconductor layer using the mask. The step of etching the first stacked semiconductor layer includes the steps of: optically monitoring an optical signal including a light component reflected from an etched surface of the substrate product for detecting an endpoint of etching; converting the optical signal to an electric signal to generate a monitoring signal; performing Fourier transform on the monitoring signal to generate a spectrum signal; and determining the endpoint detection of the etching by using the spectrum signal provided by the Fourier transform.