Focus Ring Air-Gap Structure for Plasma Etching Lifetime
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Solution Overview
Problem
Conventional plasma etching systems face issues with focus ring degradation due to fluorine-based chemistries and thermal/electric stress, leading to short lifetimes and potential wafer arcing during semiconductor fabrication.
Innovation Solution
A plasma etching system with an edge assembly featuring a focus ring that includes an air gap, reducing capacitance and potential gaps, thereby minimizing erosion and arcing by creating a more uniform plasma distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional focus ring is used in plasma etching system, then the plasma etching process can be performed, but the focus ring degrades quickly due to fluorine-based chemistries and thermal/electric stress
Solution Approach 1:
An air gap is introduced as an intermediary between the focus ring and the plasma environment. This air gap acts as a protective barrier that reduces direct exposure of the focus ring to erosive fluorine-based chemistries and thermal stress, thereby extending the focus ring's lifetime while maintaining plasma etching functionality.
Solution Approach 2:
The patent applies a sacrificial coating on the focus ring that can be easily replaced. This coating absorbs the brunt of erosion from fluorine-based chemistries, protecting the underlying focus ring structure. When the coating degrades, it can be quickly replaced without replacing the entire focus ring, thus extending operational lifetime cost-effectively.
2Reliability
If conventional focus ring design is used, then plasma etching can proceed, but wafer arcing occurs due to potential gaps and non-uniform plasma distribution
Solution Approach 1:
The air gap design creates a more uniform potential distribution across the focus ring surface. By reducing potential gaps through the introduction of the air gap, the plasma distribution becomes more uniform, preventing localized arcing events on the wafer while maintaining overall plasma etching operation.
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 air gap in the focus ring significantly prolongs its durability, reduces erosion rates, and minimizes wafer arcing, enhancing the overall reliability and efficiency of the plasma etching process.
Implementation Method 1
The air gap in the focus ring significantly prolongs its durability, reduces erosion rates, and minimizes wafer arcing, enhancing the overall reliability and efficiency of the plasma etching process.
Implementation Method 2
A plasma etching system with an edge assembly featuring a focus ring that includes an air gap, reducing capacitance and potential gaps, thereby minimizing erosion and arcing by creating a more uniform plasma distribution.
Data Source
AI summary
An edge assembly used for a plasma etching system is provided. The edge assembly includes: a focus ring peripherally surrounding an edge portion of a mounting platform mounted in the plasma etching system. The focus ring includes: a lower step portion proximate to the edge portion, the lower step portion extending vertically from a bottom surface of the focus ring to a lower step top surface; and an upper step portion distal to the edge portion, the upper step portion extending vertically from the bottom surface of the focus ring to an upper step top surface and extending radially from an upper step inner side to an upper step outer side. The focus ring is characterized by an air gap located in the upper step portion, and the air gap extends peripherally along a circumstance of the focus ring.