Edge Ring Bias Control for Stable Plasma Sheath Position
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Solution Overview
Problem
In plasma processing apparatuses, the wear of edge rings leads to a reduction in thickness, affecting the position of the plasma sheath, which is not effectively adjustable with existing technologies.
Innovation Solution
The plasma processing apparatus includes a substrate support with a bias electrode and an edge ring electrically connected to a bias power source through an impedance adjuster, allowing for adjustable negative bias and radio frequency power distribution to the edge and outer rings, enabling control over the plasma sheath thickness and density distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the edge ring is worn and thickness is reduced, then the position of the upper end of the plasma sheath above the edge ring becomes lower, but the manufacturing precision of the plasma sheath position is deteriorated
Solution Approach 1:
The patent applies a negative bias voltage to the edge ring that can be dynamically adjusted based on the edge ring thickness. This dynamic adjustment compensates for the dimensional change caused by wear, maintaining the plasma sheath position at the desired height despite the reducing edge ring thickness.
Solution Approach 2:
The patent changes the electrical parameter (bias voltage) of the edge ring to compensate for the mechanical parameter change (thickness reduction). By adjusting the bias voltage, the plasma sheath position is maintained at the correct height even as the edge ring wears down.
2Manufacturing precision
If direct-current voltage is applied to the edge ring to adjust sheath position, then the sheath position is improved, but the device complexity increases due to additional power source and control requirements
Solution Approach 1:
The bias electrode serves multiple functions: it provides the negative bias voltage to the edge ring for sheath position control, and it can also function as a radio frequency electrode for plasma generation. This multi-functionality reduces the need for separate dedicated components, thereby reducing overall device complexity.
Solution Approach 2:
The patent merges the bias voltage application function with the existing bias electrode structure. Instead of adding a completely separate power source and control system, the invention utilizes and extends the functionality of the existing bias electrode to also serve as the edge ring bias source.
3Manufacturing precision
If radio frequency power level is adjusted to control sheath position, then the position control is achieved, but the productivity is reduced due to extended adjustment time and process optimization requirements
Solution Approach 1:
The patent changes the control parameter from radio frequency power level to direct-current bias voltage. This parameter change enables more direct and rapid control of the plasma sheath position, as voltage adjustment is typically faster and more precise than radio frequency power adjustment, thereby improving productivity.
Solution Approach 2:
The patent replaces the radio frequency power control mechanism with a direct voltage control mechanism. By substituting the radio frequency power adjustment method with a bias voltage application method, the system achieves faster and more straightforward sheath position control.
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 allows for precise adjustment of the plasma sheath thickness and density distribution, maintaining optimal processing conditions despite edge ring wear and improving plasma processing efficiency.
Implementation Method 1
an impedance adjuster 83 that provides variable impedance between the bias electrode and the edge ring
Implementation Method 2
radio frequency power is supplied to the lower electrode. Plasma is formed from the gas in the chamber
Implementation Method 3
The impedance adjuster 83 provides variable impedance between the bias electrode and the edge ring
Data Source
AI summary
The disclosed plasma processing apparatus includes a chamber, a substrate support, a radio frequency power source, and a bias power source. The radio frequency power source generates radio frequency power to generate plasma. The bias power source is connected to a bias electrode of the substrate support, and generates an electric bias. An edge ring mounted on the substrate support receives a part of the electric bias through an impedance adjuster or receives another electric bias. An outer ring extends outside the edge ring in a radial direction, and receives a part of the radio frequency power or other radio frequency power.