Central RF Return Path for Uniform Multi-Station Plasma Processing
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Solution Overview
Problem
Multi-station semiconductor processing chambers with asymmetric RF return paths lead to non-uniform film deposition on wafers, especially at higher frequencies, due to the RF return path being closer to the chamber edge rather than the center, causing uneven processing across substrates.
Innovation Solution
A central RF return path is provided in the chamber by using a conductive structure, such as a conductive interface or rods, connected to the spindle or rotating mechanism, ensuring symmetric RF return paths for each station, reducing asymmetry and improving uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional RF return path through chamber walls is used, then the chamber structure is simple, but the RF return path becomes asymmetric causing non-uniform film deposition
Solution Approach 1:
The RF return path is segmented into multiple symmetric pathways through the chamber center, dividing the return current into balanced routes that pass through the central region rather than relying on asymmetric wall conduction paths
Solution Approach 2:
A central conductive structure or interface is introduced as an intermediary element to provide a symmetric RF return path through the chamber center, mediating the RF current flow between the electrode and ground in a balanced manner
2Manufacturing precision
If the RF return path is located closer to the chamber edge, then the chamber design is simpler, but non-uniformities appear on the wafer due to asymmetry
Solution Approach 1:
The invention intentionally introduces symmetry into the RF return path configuration by routing it through the chamber center, counteracting the natural asymmetry that would otherwise exist with edge-proximity return paths
3Manufacturing precision
If a central RF return path is implemented, then RF symmetry is improved, but the device complexity increases
Solution Approach 1:
The central conductive structure serves multiple functions: it provides the RF return path, acts as a mechanical support element, and maintains chamber symmetry, thereby reducing the need for separate dedicated RF return components
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 central RF return path enhances symmetry, reducing non-uniformities in film deposition across wafers by providing a more uniform distribution of RF power, leading to improved processing consistency and reduced variability.
Implementation Method 1
radio frequency (RF) power is supplied to enable excitation of gases in the form of a plasma
Data Source
AI summary
An apparatus including a multi-station processing chamber with a top plate and a bottom portion encloses stations each including a pedestal assembly. A spindle centrally located between the stations is configured to rotate about a central axis, and is electrically connected to the bottom portion. An actuator controls movement of the spindle in the Z-direction. An indexer connected to the spindle rotates with the spindle, and includes extensions each configured to interface with a corresponding substrate for substrate transfer. An electrically conductive interface movably connected to the top plate provides an RF return path. Another actuator coupled to the grounding interface controls movement of the electrically conductive interface in the Z-direction. The electrically conductive interface moves downwards in the Z-direction to make contact with the indexer when each of the plurality of extensions is parked and the spindle is moved to a lower position during plasma processing.