Ceramic Showerhead with Embedded RF Electrode
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Solution Overview
Problem
Aluminum showerheads in substrate processing systems are incompatible with chlorine-based chemistries, leading to metal contamination and plasma non-uniformity due to chemical attack and temperature-related issues, such as drooping and altered gas flow, which compromise device fabrication and introduce particle contamination.
Innovation Solution
A non-metallic ceramic showerhead assembly with a plasma-suppressing structure, featuring a back plate, face plate, and stem made of materials like aluminum nitride or aluminum oxide, with a gas plenum and RF electrode configuration that minimizes parasitic plasma discharge and allows for uniform gas distribution, and includes a plasma-suppressing structure with dielectric plates to prevent self-sustained discharges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If aluminum showerhead is used, then cost is reduced and ease of manufacture is improved, but metal contamination occurs and reliability deteriorates due to chemical attack by chlorine-based gases
Solution Approach 1:
The showerhead employs a composite structure combining ceramic material (alumina or aluminum nitride) for the gas distribution plate to prevent metal contamination, while integrating a metallic RF electrode embedded within the ceramic body to provide radio frequency power coupling. This composite approach resolves the contradiction by using non-reactive ceramic for chemical resistance while maintaining RF functionality through the embedded metal electrode.
Solution Approach 2:
The ceramic material acts as an intermediary between the chlorine-based process gases and the metallic RF electrode. The ceramic barrier prevents direct chemical attack on the metal, eliminating aluminum contamination in the deposited film while still allowing RF energy transmission to sustain plasma generation.
2Manufacturing precision
If aluminum showerhead is used, then initial gas distribution is uniform, but plasma non-uniformity and particle contamination occur over time due to fluorination and surface property changes
Solution Approach 1:
The gas distribution plate is made of ceramic material (alumina or aluminum nitride) that provides inherent resistance to fluorination and chemical attack. This composite ceramic structure maintains stable surface properties including roughness, conductivity, and emissivity over time, preventing the degradation and particle contamination associated with aluminum showerheads.
Solution Approach 2:
The invention changes the material parameter from metallic aluminum to ceramic materials with superior chemical stability. This parameter change ensures that surface properties remain constant during cleaning operations and prolonged exposure to reactive gases, maintaining manufacturing precision and eliminating reliability issues related to material degradation.
3Reliability
If RF electrode is embedded in ceramic showerhead, then metal contamination is prevented, but electrical conductivity and RF power coupling may be reduced
Solution Approach 1:
The embedded metallic RF electrode serves as an intermediary for power transmission through the ceramic showerhead. The electrode is positioned and dimensioned to provide sufficient RF power coupling to the plasma while being protected from chemical attack by the surrounding ceramic matrix, thus maintaining both reliability and power transmission efficiency.
Solution Approach 2:
The composite structure integrates a conductive metallic RF electrode within the insulating ceramic matrix. This configuration allows the metal electrode to provide the necessary electrical conductivity for RF power coupling while the ceramic exterior maintains chemical inertness and prevents contamination, resolving the contradiction between electrical performance and chemical resistance.
4Adaptability or versatility
If chlorine-based chemistry is used with aluminum showerhead, then process capability is improved, but aluminum leaching causes metal contamination in deposited film
Solution Approach 1:
The ceramic showerhead material acts as an intermediary barrier between the chlorine-based process chemistry and the substrate. This ceramic intermediate is resistant to leaching by chlorine-containing gases, thereby preventing aluminum contamination in the deposited film while still enabling the chlorine-based chemistry to function effectively for device fabrication.
Solution Approach 2:
The use of ceramic materials (alumina or aluminum nitride) in the showerhead creates a composite structure that is chemically resistant to chlorine-based processes. This material substitution eliminates the harmful aluminum leaching effect while maintaining the adaptability needed for various semiconductor fabrication processes.
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 ceramic showerhead assembly prevents metal contamination, maintains uniform gas flow and plasma distribution, and reduces parasitic plasma, enhancing the reliability and consistency of substrate processing by using ceramic materials and a dielectric plasma-suppressing structure to manage electric fields and thermal expansion.
Implementation Method 1
The showerhead distributes process gases over the substrate and serves as a radio-frequency (RF) electrode to drive the plasma
Implementation Method 2
The back plate and the face plate are made of a non-metallic material... made of materials like aluminum nitride or aluminum oxide... to manage electric fields and thermal expansion
Implementation Method 3
includes a plasma-suppressing structure with dielectric plates to prevent self-sustained discharges... to manage electric fields
Data Source
AI summary
A showerhead assembly for a substrate processing system includes a back plate connected to a gas channel. A face plate is connected adjacent to a first surface of the back plate and includes a gas diffusion surface. An electrode is arranged in one of the back plate and the face plate and is connected to one or more conductors. A gas plenum is defined between the back plate and the face plate and is in fluid communication with the gas channel. The back plate and the face plate are made of a non-metallic material.