Tunable Impedance Devices for Plasma Chamber Azimuthal Uniformity
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Solution Overview
Problem
Plasma processing chambers often exhibit azimuthal non-uniformity due to asymmetrical chamber components and RF delivery paths, leading to non-uniform processing results on wafers, which becomes critical as device sizes decrease and density increases, requiring improved methods to manage this non-uniformity.
Innovation Solution
The implementation of tunable impedance devices in ground straps and RF delivery paths, along with conductive plugs and coils, allows for adjustable impedances and current paths to compensate for inherent or foreseeable non-symmetry, ensuring azimuthal uniformity by varying the impedances and lengths of RF ground return and delivery currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If chamber components are made asymmetric to accommodate practical manufacturing constraints, then ease of manufacture is improved, but azimuthal uniformity of processing results deteriorates
Solution Approach 1:
The patent applies asymmetry by intentionally introducing asymmetric elements (ground straps, RF delivery paths, impedance devices) to counterbalance the inherent asymmetries in chamber components. This creates a compensated asymmetric system where the added asymmetries offset the original manufacturing-induced asymmetries, achieving azimuthal uniformity in processing results despite practical manufacturing constraints.
Solution Approach 2:
The patent changes electrical parameters (impedance values, current path lengths) of RF delivery paths and ground straps to compensate for physical asymmetries in chamber components. By adjusting these electrical parameters, the system achieves uniform plasma distribution and processing results across different azimuthal positions on the wafer.
2Device complexity
If RF delivery paths are kept simple and symmetric, then device complexity is reduced, but ability to compensate for non-symmetry is worsened
Solution Approach 1:
The patent segments the RF delivery system into multiple independent paths with individually adjustable impedance devices. This segmentation allows each path to be independently tuned to compensate for local asymmetries, providing the adaptability needed to correct chamber non-uniformities while maintaining a relatively simple overall structure.
Solution Approach 2:
The patent introduces tunable impedance devices that can dynamically adjust electrical parameters of RF delivery paths. This dynamic capability allows the system to adapt to different chamber configurations and compensate for various types of asymmetries, enhancing versatility without permanently increasing structural complexity.
3Manufacturing precision
If azimuthal uniformity is improved to 1% or below, then manufacturing precision is improved, but device complexity increases due to additional impedance control mechanisms
Solution Approach 1:
The patent applies local quality by placing impedance-adjustable elements at specific strategic locations around the chamber rather than uniformly throughout. This allows precise compensation of local asymmetries to achieve high azimuthal uniformity (1% or below) while minimizing the overall number of control elements and reducing system complexity.
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 effectively compensates for chamber non-symmetry and non-uniformity, achieving the necessary 1% or below azimuthal uniformity threshold, enhancing the consistency of plasma processing results across the wafer surface.
Implementation Method 1
RF energy is provided to the lower electrode 104 from RF power supply 120 via an RF conductor 122... RF energy is supplied to one or more of upper electrode 102 and lower electrode 104 in order to facilitate the ignition and sustenance of plasma
Implementation Method 2
RF current returns to ground following the direction of arrows 140 and 142... the RF delivery current (delineated, by arrows 134A and 134B) and the ground RF return current (delineated by arrows 140 and 142)
Data Source
AI summary
Methods and apparatus for modifying RF current path lengths are disclosed. Apparatus includes a plasma processing system having an RF power supply and a lower electrode having a conductive portion. There is included an insulative component disposed in an RF current path between the RF power supply and the conductive portion. There are included a plurality of RF path modifiers disposed within the insulative component, the plurality of RF path modifiers being disposed at different angular positions relative to a reference angle drawn from a center of the insulative component, whereby at least a first one of the plurality of RF path modifiers is electrically connected to the conductive portion and at least a second one of the plurality of the plurality of RF path modifiers is not electrically connected to the conductive portion.