Plasma Chamber Lower Electrode Arcing Prevention
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Solution Overview
Problem
In plasma processing chambers, arcing occurs at the vacuum brazed joints of edge rings during plasma etching of conductive materials, leading to premature wear and etch stop issues due to high chamber pressures and plasma energy exposure.
Innovation Solution
A lower electrode assembly with upper and lower edge rings having a gap with an aspect ratio sufficient to impede arcing, featuring a stepped design that increases the gap length and width, preventing plasma penetration to the brazed lines, thereby preventing arcing and extending the assembly's lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional edge rings are used with standard gap dimensions, then the assembly structure is simple and easy to manufacture, but arcing occurs at the brazed lines during plasma etching
Solution Approach 1:
The patent applies dimensionality change by transitioning from a conventional single-plane gap design to a multi-dimensional stepped gap structure. The upper edge ring includes a first gap portion extending radially outward and a second gap portion extending axially downward, creating a three-dimensional labyrinthine path. This dimensional expansion effectively increases the arc resistance without requiring proportional increases in overall component size, thereby resolving the contradiction between reliability improvement and device complexity.
Solution Approach 2:
The gap structure is segmented into multiple distinct portions: a first radial gap portion and a second axial gap portion. This segmentation creates separate functional zones that collectively impede arc propagation more effectively than a single continuous gap. The segmented design allows each portion to contribute specifically to arc resistance while maintaining manufacturing feasibility, addressing both the reliability requirement and structural complexity constraint.
2Reliability
If the gap between edge rings is increased to prevent arcing, then arc resistance improves, but the assembly size and complexity increase
Solution Approach 1:
Instead of increasing gap length in a single direction, the patent utilizes multiple spatial dimensions by creating radial and axial gap portions. This approach achieves equivalent or superior arc resistance with a more compact overall footprint, effectively resolving the contradiction between improving reliability through increased gap dimensions and controlling the physical size of the stationary object.
3Productivity
If brazed joints are used to assemble metal plates, then manufacturing efficiency is high, but arcing occurs at the brazed lines during plasma processing
Solution Approach 1:
The stepped gap structure acts as an intermediary barrier between the plasma environment and the brazed joints. Rather than attempting to make the brazed joints themselves arc-resistant, the design introduces a physical intermediary (the multi-dimensional gap) that prevents plasma contact with the vulnerable brazed lines, thereby maintaining the manufacturing efficiency of brazed assemblies while eliminating the harmful arcing effect.
Solution Approach 2:
The gap is segmented into radial and axial portions that collectively form a protective barrier around the brazed joints. This segmentation allows the brazed assembly to maintain its manufacturing efficiency while the segmented gap structure provides comprehensive protection against plasma-induced arcing at the joint locations.
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 stepped edge ring design effectively prevents arcing at the brazed lines, ensuring reliable operation for over 2000 RF bias hours without observed arcing, maintaining chamber pressure control and sustaining plasma etching processes.
Implementation Method 1
The gap has an aspect ratio of total gap length to average gap width sufficient to impede arcing at the location of the brazed line
Implementation Method 2
plasma is formed above the surface of a substrate by adding large amounts of energy to a gas (or gas mixture) at low pressure. The plasma may contain ions, free radicals, and neutral species with high kinetic energies
Implementation Method 3
By adjusting the electrical potential of the substrate, charged species in the plasma can be directed to impinge upon the surface of the substrate and thereby remove material (e.g., atoms) therefrom
Data Source
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AI summary
A lower electrode assembly for use in a plasma processing chamber comprises a metal base and upper and lower edge rings. The metal base comprises metal plates brazed together and forming a brazed line on a lower side surface of the base, an edge ring support surface extending horizontally inwardly from the lower side surface and an upper side surface above the edge ring support surface. The upper edge ring comprises a lower surface mounted on the edge ring support surface and the lower edge ring surrounds the lower side surface of the base with a gap between opposed surfaces of the upper and lower edge rings and between the lower edge ring and the outer periphery of the base. The gap has an aspect ratio of total gap length to average gap width sufficient to impede arcing at the location of the braze line.