L-Shaped CCP Electrode Structure for Edge Plasma Uniformity
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Solution Overview
Problem
Current plasma etching processes in semiconductor fabrication suffer from spatial non-uniformities in plasma characteristics due to uneven radiofrequency signal transmission, leading to inconsistent processing results on semiconductor wafers.
Innovation Solution
A new configuration of a capacitive coupled plasma source is introduced, utilizing a transverse electron beam generated in the high voltage RF or DC plasma sheath at the inner peripheral region of an L-shaped electrode, which provides additional independent control over plasma properties and uniformity by forming an edge CCP configuration, allowing for enhanced power efficiency and chemistry control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional parallel plate electrodes are used in CCP chambers, then the structure is simple and easy to manufacture, but plasma losses at the plasma periphery cannot be controlled easily and spatial non-uniformities occur
Solution Approach 1:
The upper electrode is segmented into two independent parts: a central electrode and an L-shaped electrode. The L-shaped electrode includes a horizontal section and a vertical section that extends downward toward the C-shroud, allowing independent control of plasma generation in different regions. This segmentation enables separate control of bulk plasma and edge plasma, resolving the spatial non-uniformity issue while maintaining reasonable structural complexity.
Solution Approach 2:
The L-shaped electrode is positioned with its vertical section extending toward the C-shroud to specifically address edge plasma control. By applying power independently to the L-shaped electrode, local plasma properties at the periphery can be optimized separately from the central region, enabling local quality improvement without requiring complete redesign of the entire electrode system.
2Quantity of substance
If RF power is increased to improve plasma density, then plasma generation is enhanced, but spatial non-uniformities in plasma characteristics worsen due to uneven power transmission
Solution Approach 1:
Power is divided into two independent control channels: one for the central electrode and one for the L-shaped electrode. This allows plasma density to be increased in the central region while maintaining uniform plasma characteristics at the edges, resolving the contradiction between overall plasma density enhancement and spatial uniformity.
Solution Approach 2:
The L-shaped electrode enables local optimization of plasma properties at the periphery. By independently controlling the power supplied to the L-shaped electrode, edge plasma density and uniformity can be maintained even when central plasma density is enhanced, preventing the spatial non-uniformities that would otherwise result from overall power increases.
3Reliability
If C-shroud is used as a physical barrier to contain plasma, then plasma confinement is improved, but plasma species are lost at the edge of the wafer
Solution Approach 1:
The L-shaped electrode acts as an intermediary between the central plasma region and the C-shroud barrier. Its vertical section extends toward the C-shroud, creating a controlled transition zone that guides plasma species toward the wafer surface while preventing direct contact with the C-shroud barrier, thereby reducing plasma species loss at the edge.
Solution Approach 2:
The L-shaped electrode introduces a vertical dimension to plasma control by extending downward toward the C-shroud. This vertical section creates a three-dimensional plasma confinement structure that redirects plasma flow paths, allowing plasma species to reach the wafer edge through a controlled vertical path rather than being blocked horizontally by the C-shroud.
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 configuration increases power density and uniformity across the wafer surface, improving etch rates and reducing plasma losses at the edge, while enabling low ion energy plasma applications for atomic layer deposition and etching.
Implementation Method 1
a transverse beam of electrons generated in the high voltage RF or DC plasma sheath at an inner peripheral region of a vertical section of an L-shaped electrode
Implementation Method 2
The electron beam is generated in the high voltage RF or DC plasma sheath at an inner peripheral region of a vertical section of an L-shaped electrode
Implementation Method 3
The plasma is generated by using radiofrequency signals to energize the specific reactant gases
Implementation Method 4
These radiofrequency signals are transmitted through the plasma processing volume that contains the reactant gases
Implementation Method 5
a new configuration of a capacitive coupled plasma source with additional plasma generation by transverse electron beam
Implementation Method 6
secondary electrons are accelerated in the high voltage 400 kHz or DC sheath at the vertical wall of the L-shaped electrode
Data Source
AI summary
An outer upper electrode for a capacitively coupled plasma (CCP) chamber is provided. The outer upper electrode is configured to surround an upper electrode of the CCP chamber. The outer upper electrode includes a horizontal section and a vertical section. The vertical section is substantially perpendicular to a surface of the upper electrode that faces a lower electrode of the CCP chamber. The vertical section has an inner surface that faces and surrounds the process space. The outer upper electrode can be powered with an RF source, a DC source, or coupled to filters. The outer upper electrode, when powered, is configured to generate secondary electrons that are accelerated in the high voltage RF or DC sheath transverse to the upper and lower electrodes and normal to an inner surface of the vertical section.