Movable Ground Ring for Plasma Chamber RF Confinement
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Solution Overview
Problem
In plasma processing chambers, the flow of RF current outside the confined chamber volume can lead to the formation of unconfined plasma due to RF fields in the external region, causing plasma to ignite outside the intended processing area, which results in non-uniform etching and potential etch stop issues.
Innovation Solution
A movable ground ring is introduced to provide an adjustable RF return path within the plasma processing chamber, ensuring that the RF current remains confined and preventing the ignition of unconfined plasma by creating a short RF return path between a movable substrate support assembly and a fixed ground ring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If RF current flows outside the confined chamber volume, then plasma can be generated in the external region, but unconfined plasma forms causing non-uniform etching and etch stop issues
Solution Approach 1:
The patent extracts the harmful RF current path from the external region by introducing a ground ring that captures and redirects RF current back into the chamber volume. The ground ring is positioned to intercept RF current that would otherwise flow outside the chamber, thereby preventing unconfined plasma formation while maintaining productive plasma generation within the confined volume.
Solution Approach 2:
The ground ring acts as an intermediary element between the plasma generation region and the external environment. It provides a controlled path for RF current to return to ground through the chamber volume rather than flowing externally, thus mediating the RF current flow to prevent unconfined plasma while maintaining efficient plasma generation.
2Reliability
If a fixed ground ring is used, then RF current confinement is achieved, but the system lacks adaptability to different processing conditions
Solution Approach 1:
The patent transitions from a fixed ground ring to a movable ground ring that can be adjusted vertically along the chamber axis. This dynamic positioning capability allows the ground ring to adapt to different processing conditions, substrate sizes, and plasma generation requirements while maintaining reliable RF current confinement. The movable ring can be repositioned to optimize the RF return path for various operational scenarios.
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 solution effectively confines the RF current and plasma within the processing chamber, enhancing the uniformity of plasma etching and preventing etch stop issues by eliminating the need for a wafer port through the confinement ring, thus maintaining controlled plasma formation and improving processing accuracy.
Implementation Method 1
The movable ground ring comprises: an annular bottom wall having a plurality of centering slots in a lower surface thereof; a sidewall extending upwardly from an inner periphery of the bottom wall, the sidewall having an inner surface configured to surround an outer periphery of the fixed ground ring
Implementation Method 2
Plasma can be generated by subjecting suitable process gases in a plasma processing chamber to radio frequency (RF) power. Flow of RF current in the plasma processing chamber can affect the processing.
Data Source
AI summary
A movable ground ring of a movable substrate support assembly is described. The movable ground ring is configured to fit around and provide an RF return path to a fixed ground ring of the movable substrate support assembly in an adjustable gap capacitively-coupled plasma processing chamber wherein a semiconductor substrate supported in the substrate support assembly undergoes plasma processing.