Ring Cavity Non-Ambipolar Plasma Uniformity Control
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Solution Overview
Problem
Plasma processing systems face challenges in maintaining uniform plasma density across semiconductor substrates due to ion loss to the chamber wall, leading to non-uniform etching or deposition rates, particularly at the edge of the substrate.
Innovation Solution
Incorporating a ring cavity surrounding the plasma chamber wall, which is in fluid communication with the plasma chamber and equipped with an electrode connected to a power source, to alter the boundary potential and facilitate non-ambipolar diffusion of ions and electrons, thereby maintaining a uniform plasma density profile by generating an electric pressure that prevents ion loss to the chamber wall.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a large distance or gap is used between the plasma source and the substrate, then the chamber wall can be disposed between the plasma source and the substrate for structural reasons, but ions and electrons in the plasma are influenced by the potential difference between the plasma and the chamber wall, causing ions to migrate towards the chamber wall instead of the substrate, resulting in plasma density non-uniformity
Solution Approach 1:
A ring electrode is introduced as an intermediary component between the plasma source and the substrate. This ring electrode generates a tailored potential field that acts as a mediator to guide ion transport, preventing ions from migrating to the chamber wall and ensuring uniform plasma density distribution across the substrate surface.
Solution Approach 2:
The potential distribution in the plasma chamber is actively controlled by applying specific voltages to the ring electrode. By changing the electrical parameter (potential) in the plasma environment, the ion migration path is controlled, preventing ion loss to the chamber wall and maintaining uniform plasma density despite the large chamber geometry.
2Ease of manufacture
If the chamber wall is disposed between the plasma source and the substrate, then structural configuration is achieved, but the boundary potential or plasma sheath at the chamber wall causes loss of charge particles to the chamber wall, leading to plasma density non-uniformity and substrate processing non-uniformity
Solution Approach 1:
The ring electrode serves as an intermediary that modifies the electric field environment between the plasma and chamber wall. It creates a controlled potential gradient that prevents direct interaction between ions and the chamber wall, eliminating the harmful plasma sheath effect while preserving the structural chamber configuration.
Solution Approach 2:
The ring electrode applies a preliminary electrical action (potential field) that counteracts the harmful effect of the chamber wall before ions can reach it. By establishing this opposing potential field in advance, ion migration toward the chamber wall is prevented, and uniform plasma density is maintained across the substrate.
3Manufacturing precision
If boundary potential or plasma sheath at the chamber wall is altered to diffuse ions into the plasma chamber, then plasma density uniformity may be improved, but a ring cavity surrounding the chamber wall with an electrode requires additional system complexity
Solution Approach 1:
The chamber wall is segmented by introducing a ring electrode structure that circumscribes the plasma chamber. This segmentation allows independent control of the potential field in different regions, enabling precise manipulation of ion transport and plasma density distribution without modifying the entire chamber structure.
Solution Approach 2:
The solution moves from two-dimensional planar electrode configurations to a three-dimensional ring electrode structure. This dimensional change enables the creation of a tailored potential field that wraps around the plasma chamber, providing omnidirectional control over ion transport and achieving uniform plasma density more effectively.
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 ensures more uniform plasma density exposure to the substrate, enhancing processing uniformity from the center to the edge, reducing processing non-uniformities and improving the consistency of semiconductor device fabrication.
Implementation Method 1
The non-ambipolar diffusion may occur between regions of different localized plasma potential. The diffusion may include the exchange of ions and electrons between the regions, in that the first region (e.g., inside the plasma chamber) may diffuse electrons towards a second plasma region and that the second region (e.g., ring cavity) may diffuse ions towards the first plasma region in a systematic manner.
Implementation Method 2
The electric pressure may be enabled by forming a potential difference proximate to the chamber wall that may alter the plasma density or plasma sheath proximate to the chamber wall, such that the plasma density across the plasma chamber may be more uniform.
Implementation Method 3
The plasma chamber may include one or more plasma sources that can emit electromagnetic energy to ionize gas that is delivered via a gas delivery system.
Data Source
AI summary
This disclosure relates to a plasma processing system for controlling plasma density near the edge or perimeter of a substrate that is being processed. The plasma processing system may include a plasma chamber that can receive and process the substrate using plasma for etching the substrate, doping the substrate, or depositing a film on the substrate. This disclosure relates to a plasma processing system that may be configured to enable non-ambipolar diffusion to counter ion loss to the chamber wall. The plasma processing system may include a ring cavity coupled to the plasma processing system that is in fluid communication with plasma generated in the plasma processing system. The ring cavity may be coupled to a power source to form plasma that may diffuse ions into the plasma processing system to minimize the impact of ion loss to the chamber wall.