RF Powered Edge Ring Assembly for Plasma Sheath Control
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Solution Overview
Problem
Current semiconductor wafer processing technologies face challenges in achieving uniformity at the edge and extreme edge regions of wafers due to non-uniform plasma composition and electrical discontinuities, leading to issues like ion focusing and critical dimension variations.
Innovation Solution
An RF powered edge ring assembly with a buried electrode is used to control the plasma sheath boundary at the wafer edge, reducing ion tilting and focusing by enabling sheath continuity over the edge ring, and optimizing ion to neutral flux ratios through adjustable voltage and phase differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dielectric edge rings are used to prevent plasma exposure to the electrostatic chuck, then the electrostatic chuck is protected from processing plasma, but electrical discontinuity is created at the wafer edge causing ion focusing and critical dimension non-uniformity
Solution Approach 1:
A conductive ring is introduced as an intermediary component between the dielectric edge ring and the electrostatic chuck. This conductive ring serves as a mediator that maintains electrical continuity while still providing plasma protection, thereby resolving the contradiction between protecting the ESC and maintaining manufacturing precision at the wafer edge
Solution Approach 2:
The edge ring assembly uses a composite structure combining dielectric and conductive materials. The dielectric portion provides plasma isolation while the conductive portion maintains electrical continuity, creating a multi-material solution that simultaneously achieves both protection and uniformity
2Reliability
If conventional edge rings with fixed conductivity are used, then plasma protection is provided, but no tuning capability exists for mitigating ion-focusing and ion trajectories
Solution Approach 1:
The edge ring assembly is transformed from a static, fixed-conductivity component to a dynamic, adjustable system. The conductive ring's electrical properties can be tuned by adjusting the bias voltage applied to the electrostatic chuck, enabling real-time control of ion trajectories and sheath bending while maintaining plasma protection
Solution Approach 2:
The system enables tuning of the conductive ring's effective conductivity by changing the bias voltage parameter on the electrostatic chuck. This parameter adjustment allows control over the degree of sheath bending and ion focusing, providing adaptability while maintaining the protective function
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 allows for precise control of ion trajectories and flux at the wafer edge, enhancing critical dimension uniformity and reducing non-uniformities, thereby improving fabrication yield and wafer profile tuning.
Implementation Method 1
control over the plasma sheath boundary at the extreme wafer edge
Implementation Method 2
edge-localized ion trajectory control
Implementation Method 3
powered at a low RF frequency (voltages are high at low frequencies)
Implementation Method 4
electrostatic chuck (ESC) that is configured for electrical connection
Data Source
AI summary
An edge ring assembly for a plasma processing chamber is provided, including: an edge ring configured to surround an electrostatic chuck (ESC) that is configured for electrical connection to a first RF power supply, the ESC having a top surface for supporting a substrate and an annular step surrounding the top surface, the annular step defining an annular shelf that is lower than the top surface; an annular electrode disposed below the edge ring in the annular step and above the annular shelf; a dielectric ring disposed below the annular electrode for isolating the annular electrode from the ESC, the dielectric ring positioned in the annular step over the annular shelf; and, a plurality of insulated connectors disposed through the ESC and through the dielectric ring, each of the plurality of insulated connectors providing electrical connection between a second RF power supply and the annular electrode.