Tapered Upper Electrode for Plasma Uniformity in Etching
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Solution Overview
Problem
Substrate processing systems face challenges with non-uniform plasma distribution and resulting etch non-uniformity, particularly in high aspect ratio etching applications, leading to profile tilting and critical dimension non-uniformity.
Innovation Solution
The use of an upper electrode with a tapered, plasma-facing lower surface that varies in thickness radially to control plasma distribution, incorporating features such as sloped, curved, or stepped designs to minimize plasma non-uniformity and enhance uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional upper electrode with uniform thickness is used, then the device structure is simple, but plasma distribution becomes non-uniform with center-peaked density
Solution Approach 1:
The upper electrode is designed with non-uniform thickness where the central region has a first thickness and the peripheral region has a second thickness different from the first. This local variation in electrode geometry creates corresponding variations in the plasma sheath thickness, thereby achieving more uniform plasma density distribution across the substrate surface.
Solution Approach 2:
The electrode thickness parameter is deliberately changed from a uniform value to a spatially varying value. By adjusting the thickness parameter across different regions of the electrode, the plasma generation characteristics are modified to reduce center-peaked density and improve overall uniformity.
2Manufacturing precision
If the upper electrode thickness is varied to improve plasma uniformity, then plasma distribution improves, but the manufacturing complexity increases
Solution Approach 1:
The electrode is manufactured with distinct regional thickness variations - a central region with one thickness and peripheral regions with another thickness. This local quality differentiation addresses etch uniformity requirements while allowing for standardized manufacturing processes for each region.
Solution Approach 2:
The electrode structure is segmented into different thickness zones (central region and peripheral region) that can be manufactured separately or formed through multi-step processes. This segmentation makes the complex geometry more manageable in terms of fabrication and quality control.
3Manufacturing precision
If a tapered electrode design is used to control plasma distribution, then plasma uniformity improves, but the electrode geometry becomes more complex
Solution Approach 1:
The electrode features localized geometric variations where specific regions (central vs. peripheral) have different thickness characteristics. This local quality approach controls plasma distribution and profile uniformity without requiring complete geometric reconfiguration of the entire electrode.
Solution Approach 2:
The electrode incorporates curved or tapered surfaces instead of flat geometries. The gradual thickness transition from center to periphery creates smooth geometric variations that effectively control plasma sheath formation while maintaining manufacturable shapes.
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
The tapered upper electrode design reduces center-peaked plasma density, improves plasma uniformity, and minimizes etch non-uniformity and profile tilting, enhancing processing consistency.
Implementation Method 1
The second radius corresponds to a third radius of an electric field generated below the upper electrode during operation of the substrate processing system
Implementation Method 2
The lower surface includes a first portion and a second portion and is plasma-facing
Data Source
AI summary
An upper electrode for use in a substrate processing system includes a lower surface. The lower surface includes a first portion and a second portion and is plasma-facing. The first portion includes a first surface region that has a first thickness. The second portion includes a second surface region that has a varying thickness such that the second portion transitions from a second thickness to the first thickness.