Slot-Shaped Faceplate Holes Suppress Hollow Cathode Discharge
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Solution Overview
Problem
Substrate processing systems face challenges with parasitic plasma generation, specifically hollow cathode discharge (HCD), which can be detrimental to hardware due to power dissipation in small volumes, and altering hole sizes to prevent HCD can lead to non-uniform gas distribution and increased machining costs.
Innovation Solution
The use of a faceplate with a unique geometry, featuring slot-shaped holes with specific dimensions relative to the plasma sheath thickness, to prevent HCD while maintaining efficient gas flow, including a first size dimension less than 3 plasma sheath thicknesses and a second size dimension greater than 2 times the first, reducing the number of holes needed and optimizing flow conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If circular holes are used in the faceplate, then gas distribution is achieved, but hollow cathode discharge occurs causing power dissipation and hardware damage
Solution Approach 1:
The patent changes the geometric parameters of the holes from circular to slot-shaped, with specific dimension ratios (second dimension greater than 2 times the first dimension) and size constraints (first dimension less than 3 plasma sheath thicknesses). This parameter transformation eliminates the hollow cathode effect by preventing the formation of a cathode cavity, thereby stopping parasitic plasma generation and power dissipation.
2Object-affected harmful factors
If hole sizes are altered to prevent HCD, then parasitic plasma is suppressed, but gas distribution uniformity deteriorates
Solution Approach 1:
The patent transforms the hole geometry from circular to slot-shaped with controlled aspect ratios, maintaining appropriate gas flow characteristics while preventing HCD. The specific dimensional constraints ensure that the slots provide sufficient gas distribution uniformity across the substrate surface.
Solution Approach 2:
The patent transitions from isotropic circular holes to anisotropic slot-shaped openings, utilizing dimensional transformation to achieve both HCD suppression and gas distribution uniformity. The elongated slot geometry provides different conductance characteristics in different directions, optimizing both plasma suppression and gas flow distribution.
3Quantity of substance
If circular holes are used, then gas flow is achieved, but the number of holes required increases leading to higher machining costs
Solution Approach 1:
The patent changes the hole geometry to slot-shaped configurations with optimized dimensions, which provide superior gas flow conduction per opening compared to circular holes. This reduces the total number of holes required in the faceplate, thereby lowering machining complexity and manufacturing costs.
Solution Approach 2:
By transitioning from circular to slot-shaped geometry, the patent increases the effective gas conduction area in the direction of gas flow while maintaining compact footprints. This dimensional optimization allows fewer openings to achieve the same or better gas distribution, reducing manufacturing 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 suppresses HCD, reduces the number of holes required, and enhances gas flow uniformity, making the substrate processing system more cost-effective and efficient by minimizing hardware damage and machining costs.
Implementation Method 1
a capacitively coupled plasma (CCP) generator may be used to generate plasma in the processing chamber
Implementation Method 2
The first size dimension is less than 3 plasma sheath thicknesses of plasma generated by the plasma processing chamber
Data Source
AI summary
A faceplate for a gas distribution system of a plasma processing chamber includes a faceplate body having a first surface, a second surface opposite to the first surface and a side surface. A first plurality of holes in the faceplate body extends from the first surface to the second surface. At least some of the first plurality of holes has a first size dimension and a second size dimension in a plane parallel to the first surface. The first size dimension is transverse to the second size dimension. The first size dimension is less than 3 plasma sheath thicknesses of plasma generated by the plasma processing chamber. The second size dimension is greater than 2 times the first size dimension.