Shield Ring Voltage Control for Plasma Sheath Flatness
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Solution Overview
Problem
The increasing complexity of workpieces in plasma processing chambers leads to non-uniform ion incident angles due to voltage and geometrical mismatches between the workpiece and shield ring, causing radial non-uniformity and affecting device performance, especially at the outer edge of the workpiece.
Innovation Solution
A workpiece processing apparatus with independent control of voltage applied to the shield ring and workpiece, using a platen with a dielectric material, a bias electrode, and a shield ring, where the ring electrode and bias electrode can be separately powered to match and adjust voltages, ensuring a flat plasma sheath and uniform ion angles across the workpiece.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the shield ring and workpiece are processed with a single voltage control system, then the device complexity is reduced, but the manufacturing precision of ion incident angles deteriorates due to voltage mismatch
Solution Approach 1:
The voltage control system is segmented into two independent parts: one for controlling the workpiece voltage and another for controlling the shield ring voltage. This allows separate optimization of voltages for each component, enabling precise control of ion incident angles at the workpiece surface while maintaining manageable system complexity through modular architecture.
Solution Approach 2:
Different voltage conditions are applied to different parts of the system - the workpiece receives a voltage optimized for its processing requirements, while the shield ring receives a separately optimized voltage. This local differentiation ensures that ion incident angles are uniform across the workpiece surface, particularly at the outer edge, without requiring the entire system to operate under a single voltage regime.
2Device complexity
If the shield ring geometry is fixed, then the device complexity is reduced, but the manufacturing precision of radial uniformity deteriorates due to geometrical mismatch
Solution Approach 1:
The shield ring system is made dynamically adjustable through independent voltage control, allowing the electrical configuration to adapt to geometric mismatches. By varying the shield ring voltage independently, the system compensates for geometric imperfections and maintains uniform ion incident angles across different radial positions of the workpiece.
Solution Approach 2:
The voltage parameter of the shield ring is changed and optimized independently from the workpiece voltage. This parameter adjustment allows compensation for fixed geometric mismatches between the shield ring and workpiece, achieving radial uniformity in ion incident angles without requiring complex geometric adjustments.
3Ease of operation
If voltage drift is not compensated, then the ease of operation is improved, but the manufacturing precision of ion incident angles deteriorates due to charging effects
Solution Approach 1:
The independent dual voltage control system enables separate monitoring and adjustment of workpiece and shield ring voltages. This feedback capability allows detection and compensation of voltage drift in either component, maintaining consistent ion incident angles despite charging effects during processing operations.
Solution Approach 2:
By segmenting the voltage control into independent channels for the workpiece and shield ring, the system can independently compensate for voltage drift in each component. This segmentation maintains manufacturing precision through targeted adjustments while preserving ease of operation through modular control architecture.
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 solution ensures that the deviation in ion incident angles is minimized to less than 0.5° across the workpiece, improving processing uniformity and precision, particularly at the outer edge, and compensates for geometric and voltage mismatches, enhancing the performance of processes like etching.
Implementation Method 1
the voltage generated on the surface of the shield ring to match that of the workpiece, which causes the plasma sheath above the workpiece to be flat
Implementation Method 2
the angle at which ions strike the workpiece along that outer edge
Implementation Method 3
the ring height measurement system comprises a laser
Data Source
AI summary
A workpiece processing apparatus allowing independent control of the voltage applied to the shield ring and the workpiece is disclosed. The workpiece processing apparatus includes a platen. The platen includes a dielectric material on which a workpiece is disposed. A bias electrode is disposed beneath the dielectric material. A shield ring, which is constructed from a metal, ceramic, semiconductor or dielectric material, is arranged around the perimeter of the workpiece. A ring electrode is disposed beneath the shield ring. The ring electrode and the bias electrode may be separately powered. This allows the surface voltage of the shield ring to match that of the workpiece, which causes the plasma sheath to be flat. Additionally, the voltage applied to the shield ring may be made different from that of the workpiece to compensate for mismatches in geometries. This improves uniformity of incident angles along the outer edge of the workpiece.