Curved Gas Diffuser Plate for PECVD Film Uniformity
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Solution Overview
Problem
Large area plasma-enhanced chemical vapor deposition (PECVD) systems face challenges in achieving uniform film thickness and property uniformity, particularly for SiN and α-Si films, due to non-uniform plasma distribution and increased deposition rates at the center of substrates, leading to 'dome-shaped' thickness profiles with thicker films at the center and thinner films at the edges.
Innovation Solution
A gas distribution plate assembly with a diffuser plate featuring a curvature and varying hollow cathode cavity density, volume, or surface area from the center to the edge, along with concentric zones of increasing cavity size, is used to enhance plasma ionization and uniformity, addressing the non-uniformity issues by modifying the plasma distribution and electrode spacing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a flat diffuser plate with uniform gas distribution is used, then the device complexity is low, but film thickness uniformity deteriorates due to center-thick deposition profiles
Solution Approach 1:
The patent applies local quality by varying the cavity depth across different regions of the diffuser plate. Specifically, the cavity depth increases from the center region to the edge region, creating non-uniform plasma distribution that compensates for the natural center-thick deposition tendency. This local variation in cavity depth allows different parts of the diffuser plate to perform different functions, achieving uniform film thickness across the substrate.
Solution Approach 2:
The patent employs curvature by designing the downstream side of the diffuser plate with a curved surface rather than a flat one. The curved surface, with cavities of varying depths, creates a non-uniform plasma distribution pattern that matches the desired film thickness profile. This curvature approach transforms the uniform gas distribution into a controlled non-uniform plasma distribution, solving the center-thick deposition problem.
2Manufacturing precision
If hollow cathode cavities are added to enhance plasma ionization, then plasma uniformity improves, but device complexity increases
Solution Approach 1:
The patent applies local quality by varying the cavity depth across different regions of the diffuser plate. Specifically, the cavity depth increases from the center region to the edge region, creating non-uniform plasma distribution that compensates for the natural center-thick deposition tendency. This local variation in cavity depth allows different parts of the diffuser plate to perform different functions, achieving uniform film thickness across the substrate.
Solution Approach 2:
The patent employs parameter changes by systematically varying the cavity depth parameter across the diffuser plate surface. The cavity depth is changed from a uniform value to a graded value that increases from center to edge. This parameter variation directly controls the plasma ionization level in different regions, enhancing plasma uniformity while maintaining a relatively simple overall structure.
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 solution improves film thickness and property uniformity across large substrates, expanding the process window for α-Si films and effectively addressing the 'center thick' uniformity problem for SiN films, making it suitable for mass production.
Implementation Method 1
A gas distribution plate assembly with a diffuser plate featuring a curvature and varying hollow cathode cavity density, volume, or surface area from the center to the edge
Implementation Method 2
Plasma enhanced chemical vapor deposition (PECVD) is generally employed to deposit thin films on a substrate
Data Source
AI summary
Embodiments of a gas distribution plate for distributing gas in a processing chamber are provided. In one embodiment, a gas distribution assembly for a plasma processing chamber comprises a diffuser plate with gas passages passing between its upstream and downstream sides and hollow cathode cavities at the downstream side of the gas passages. The downstream side of the diffuser plate has a curvature to improve the thickness uniformity and film property uniformity of thin films deposited by PECVD, particularly SiN and amorphous silicon films. The curvature is preferably described by an arc of a circle or ellipse, the apex thereof located at the center point of the diffuser plate. In one aspect, the hollow cathode cavity volume density, surface area density, or the cavity density of the diffuser increases from the center of the diffuser to the outer edge. Methods for manufacturing such a diffuser plate are also provided.