Central RF Return Path Layout for Uniform Multi-Station Deposition
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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, particularly at higher frequencies, due to the RF return path being closer to the chamber edge rather than the center, causing asymmetry and non-uniformities.
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 non-uniformities.
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 by introducing a central conductive structure (spindle/indexer) that divides the return current flow into balanced paths, preventing asymmetry and ensuring uniform film deposition across the wafer surface
Solution Approach 2:
A central conductive structure (spindle or indexer) is introduced as an intermediary element between the RF power source and ground, serving as a dedicated RF return path that ensures symmetric current distribution and eliminates the asymmetry caused by wall-based return paths
2Manufacturing precision
If the RF return path is located closer to the chamber edge, then the chamber design is simpler, but asymmetry increases leading to non-uniformities on wafers
Solution Approach 1:
The invention deliberately introduces a symmetric element (central conductive structure) into an otherwise asymmetric configuration, creating a balanced RF return path that counteracts the inherent asymmetry of edge-located paths and ensures uniform processing across all wafer positions
3Stability of the object's composition
If a central RF return path is implemented, then RF return path symmetry increases, but the chamber structure becomes more complex
Solution Approach 1:
The central conductive structure (spindle/indexer) performs multiple functions: it serves as the RF return path, supports wafer processing operations, and provides structural stability, thereby achieving symmetry improvement without proportionally increasing overall chamber complexity
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 increases symmetry, leading to more uniform film deposition across wafers by minimizing non-uniformities, enhancing the consistency and quality of processing in multi-station chambers.
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.