Odd Harmonic Mixing for Plasma Etch Ion Control
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Solution Overview
Problem
Current plasma processing technologies face challenges in tailoring ion energy distribution functions for high aspect ratio etching, as existing methods fail to effectively control ion energy and flux, particularly when using even harmonics which can reduce ion flux and are not suitable for achieving optimal etch performance.
Innovation Solution
The implementation of odd harmonic mixing in plasma processing systems, where odd harmonics of RF signals are modified in amplitude and phase to increase peak ion energy and flux, enabling the manipulation of the ion energy distribution function for enhanced etch performance by combining these harmonics to generate an RF signal waveform approximating a square wave.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If even harmonics are used to modify RF signals, then ion flux is reduced, but this is not suitable for achieving optimal etch performance in high aspect ratio features
Solution Approach 1:
The patent inverts the conventional approach by using odd harmonics instead of even harmonics to modify the RF signal. This inversion allows the system to increase ion flux and peak ion energy simultaneously, resolving the contradiction between maintaining ion flux and achieving optimal etch performance in high aspect ratio features
Solution Approach 2:
The patent changes the harmonic parameters by selectively applying odd harmonics (3rd, 5th, 7th, etc.) to the RF signal while controlling their amplitudes and phases. This parameter modification enables tailoring of the ion energy distribution function to achieve both high ion flux and optimal etch performance, directly addressing the contradiction
2Productivity
If odd harmonics are mixed with modified amplitude and phase, then peak ion energy and ion flux are increased, but system complexity increases due to multiple RF power supplies and signal combination circuits
Solution Approach 1:
The patent segments the RF signal generation into multiple independent odd harmonic power supplies, each generating a specific harmonic frequency. This segmentation allows independent control of amplitude and phase for each harmonic, enabling precise tailoring of ion energy distribution while managing system complexity through modular architecture
Solution Approach 2:
The patent merges multiple odd harmonic RF signals into a single composite signal that is applied to the plasma chamber. The adder circuit combines the harmonics with controlled amplitudes and phases, creating a waveform that approximates a square wave to achieve enhanced ion flux and peak ion energy for improved etch performance
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 allows for controlled ion energy and flux manipulation, significantly increasing the etch rate for high aspect ratio features, as demonstrated by the graphs showing improved ion energy and flux control, thereby optimizing the etching process.
Implementation Method 1
mixing a number of odd harmonics of the bias frequency after modifying an amplitude and/or a phase of one or more of the odd harmonics
Implementation Method 2
The impedance matching circuit outputs an nth modified odd harmonic RF signal upon receiving the nth odd harmonic RF signal
Data Source
AI summary
Systems and methods for controlling a process applied to a substrate within a plasma chamber are described. The systems and methods include generating and supplying odd harmonic signals and summing the odd harmonic signals to generate an added signal. The added signal is supplied to an electrode within the plasma chamber for processing the substrate. The use of odd harmonic signals facilitates high aspect ratio etching of the substrate.