Plasma Endpoint Detection for Low Open Area Etch Signals
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Solution Overview
Problem
Conventional endpoint detection methods struggle with precise detection in semiconductor etch operations, especially for high aspect ratio and low open area features, due to weak plasma emission signals being masked by background noise and chamber interactions.
Innovation Solution
A method involving obtaining a reference emission curve during an etch operation, calculating a ratio curve between the reference and real-time plasma emissions, and determining the endpoint based on an inflection point in this ratio curve to filter out background noise and enhance sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional endpoint detection methods are used, then detection is feasible for standard etch applications, but detection precision deteriorates for high aspect ratio and low open area features due to weak plasma emission signals being masked by background noise
Solution Approach 1:
The patent extracts and removes the background noise component from the plasma emission signal by separately measuring and subtracting the background emission spectrum, thereby isolating the true endpoint detection signal from interfering background noise in high aspect ratio and low open area etch applications
Solution Approach 2:
The patent introduces an intermediary background emission measurement that acts as a mediator between the raw plasma emission signal and the processed endpoint detection signal, allowing the weak endpoint signal to be differentiated from background noise through comparative analysis
2Reliability
If conventional endpoint detection is used, then simple equipment is sufficient, but detection reliability deteriorates for features with aspect ratio greater than 30:1 or open area less than 3%
Solution Approach 1:
The patent performs preliminary background emission measurement and characterization before conducting the actual endpoint detection, preparing reference data and calibration information in advance to enable reliable detection in high aspect ratio and low open area applications without requiring complex real-time processing
Solution Approach 2:
The patent changes the measurement parameters by separately measuring background emission intensity and plasma emission intensity at different stages, and by analyzing spectral parameters across multiple wavelengths, thereby extracting reliable endpoint information from weak signals in challenging geometries
3Manufacturing precision
If conventional real-time emission analysis is used, then the system is simple to operate, but manufacturing precision deteriorates due to inability to detect weak endpoint signals in high aspect ratio features
Solution Approach 1:
The patent replaces simple intensity-based detection with a spectral analysis approach that examines emission characteristics across multiple wavelengths and temporal profiles, substituting basic measurement mechanics with more sophisticated spectral characterization to achieve precise endpoint detection in high aspect ratio features
Solution Approach 2:
The patent employs periodic sampling and analysis of plasma emission spectra throughout the etch process, using time-resolved measurements at multiple stages to identify the endpoint through characteristic changes in emission patterns rather than relying on a single threshold detection event
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 reliable endpoint detection for high aspect ratio and low open area etch operations, reducing the risk of overetching or underetching by filtering out emission background noise and improving sensitivity without requiring sophisticated new equipment.
Implementation Method 1
conventional endpoint detection in etch applications rely on the analysis of emission trends or spectra collected in real time
Data Source
AI summary
Disclosed herein is a method for determining the endpoint of an etch operation used for forming high aspect ratio features and/or over low open area (<1%) on a substrate in a processing chamber. The method begins by obtaining a reference emission curve. An etch operation is performed on a patterned substrate. A plasma optical emission intensity is measured for each of the etch cycles. A differential curve between the reference emission and the plasma optical emissions is calculated. And endpoint is determined for the etch operation on the first substrate based on an inflection point detection or other unique features through pattern recognition in the differential curve for stopping the etch of the first substrate.