Symmetrical Remote Plasma Source for Ion Energy Control
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Solution Overview
Problem
In plasma processing systems, remote plasma sources face challenges in generating high-density plasmas while minimizing ion sputtering of the hardware, which leads to contamination of the workpiece due to high-energy ions from capacitively coupled plasma sources.
Innovation Solution
The use of symmetrical, capacitively coupled plasma sources with opposing electrodes of equal areas and sloping interior surfaces reduces plasma potential, minimizing ion energy and sputtering, and incorporates a gas distribution system to maintain high-density plasma generation across a wide pressure range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a capacitively coupled plasma source is used to generate high density plasma, then plasma density increases, but ion energy increases causing sputtering and contamination
Solution Approach 1:
The patent employs asymmetrical electrode design where the powered electrode has a smaller surface area than the ground electrode. This asymmetry creates a potential well that confines electrons and enhances plasma density while directing ions toward the larger ground electrode, reducing sputtering of critical components. The asymmetrical geometry allows independent optimization of plasma generation and ion control.
Solution Approach 2:
The patent creates a potential well between the electrodes by applying RF power to the smaller electrode while grounding the larger electrode. This establishes a controlled potential distribution that confines electrons in the plasma region while guiding ions toward the ground electrode, achieving both high plasma density and reduced ion damage to chamber surfaces.
2Quantity of substance
If high pressure operation is used to increase gas density, then plasma density increases, but ion energy increases causing sputtering
Solution Approach 1:
The asymmetrical electrode configuration with the powered electrode having smaller area than the ground electrode creates favorable conditions for high pressure operation. The geometry enhances electron confinement through the potential well, maintaining high plasma density at elevated pressures while directing ion flux toward the larger ground electrode, reducing sputtering even at high gas densities.
Solution Approach 2:
The patent utilizes the asymmetrical electrode design to enable operation across a wide pressure range. By changing the pressure parameter and maintaining the asymmetrical geometry, the system achieves high plasma density at high pressures while the potential well continues to confine electrons and direct ions, preventing sputtering across varying operational conditions.
3Ease of manufacture
If symmetrical electrode design is used, then manufacturing is simplified, but plasma potential is higher increasing ion energy
Solution Approach 1:
The patent deliberately introduces asymmetry in electrode dimensions, with the powered electrode having smaller surface area than the ground electrode. This asymmetry is strategically designed to create the potential well needed for electron confinement and ion direction, accepting the increased manufacturing complexity as necessary to achieve the desired plasma characteristics and reduced ion energy.
Solution Approach 2:
The asymmetrical design allows different regions of the plasma source to have different functions: the smaller powered electrode focuses on electron generation and confinement, while the larger ground electrode handles ion collection. This local differentiation of electrode roles optimizes plasma potential control and ion energy reduction while maintaining effective plasma generation.
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 effectively reduces metal contamination and expands the process window by maintaining low plasma potential and high-density plasma generation, enhancing productivity and operational flexibility.
Implementation Method 1
A capacitively coupled plasma source (driven with an RF or DC voltage) is therefore preferred in the remote plasma source
Implementation Method 2
A high density plasma is desired to achieve high etch rates on the workpiece
Implementation Method 3
the ions produced in a capacitively coupled remote plasma source have high energy and can bombard the remote plasma source surfaces, generating particle and/or metal contaminants
Data Source
AI summary
A remote plasma source is enclosed by a pair of counter electrodes of conical or similar shape that are mirror images of one another and connected across a plasma power source.