Dual Gas Injection Electrode Assembly for Etching
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Solution Overview
Problem
Conventional plasma processing chambers suffer from substrate contamination due to ion bombardment of metal electrodes, particularly during dry etch processes using ammonia and fluorine-containing gases, which generates unwanted aluminum fluoride particles.
Innovation Solution
The electrode assembly features a dual gas injection system with a hollow cathode electrode and a ground anode electrode, where the first etchant gas is ionized within the cathode and filtered to allow radicals into a mixing volume, while the second etchant gas is introduced separately through a gas injection ring, reducing the RF power required for plasma breakdown and minimizing substrate contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher RF power is applied to the cathode electrode to break down both ammonia and fluorine-containing gases, then the plasma generation efficiency is improved, but substrate contamination from ion bombardment of the cathode electrode is aggravated
Solution Approach 1:
The gas delivery system is segmented into multiple channels: a first gas channel for fluorine-containing gas and a second gas channel for ammonia gas. This segmentation allows each gas to be delivered and processed separately, enabling the fluorine-containing gas to be broken down with lower RF power while ammonia is introduced separately to react with fluorine radicals, thus reducing ion bombardment contamination while maintaining plasma generation efficiency.
Solution Approach 2:
A mixing volume is introduced as an intermediary region between the gas delivery channels and the plasma reaction zone. In this mixing volume, fluorine radicals generated from the first gas channel mix with ammonia molecules from the second gas channel before reaching the substrate. This intermediary mixing region allows chemical reactions to occur without requiring high RF power directly at the cathode, thereby reducing ion bombardment while maintaining effective etching.
2Device complexity
If conventional single gas delivery system is used, then the device complexity is low, but the substrate contamination from electrode ion bombardment cannot be effectively reduced
Solution Approach 1:
The gas delivery system is divided into distinct first and second gas channels with separate delivery paths for fluorine-containing gas and ammonia gas. This segmentation enables independent control of each gas flow and timing, allowing optimization of plasma generation while minimizing contamination, at the cost of increased system complexity.
Solution Approach 2:
The invention adds a temporal dimension to gas delivery by introducing ammonia gas after initial fluorine plasma is established, rather than mixing gases simultaneously. This time-sequence control, implemented through separate gas channels and a mixing volume, allows the system to achieve contamination reduction while managing the complexity through structured multi-stage gas introduction.
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 configuration significantly reduces substrate contamination by lowering the RF power needed for plasma generation, allowing for more flexible process conditions and improved etching performance without increasing contamination from electrode ion bombardment.
Implementation Method 1
an electrical power source excites the gases into a plasma state
Implementation Method 2
the first etchant gas is ionized within the cathode
Implementation Method 3
the second etchant gas is introduced separately through a gas injection ring into a mixing volume
Data Source
AI summary
Implementations of the present disclosure relate to an electrode assembly for a processing chamber. In one implementation, the electrode assembly includes a cathode electrode having an inner volume and a ground anode electrode spaced apart from the cathode electrode. A first etchant gas is introduced through the cathode electrode and into the inner volume. The first etchant gas is ionized within the inner volume. The ionized first etchant gas is filtered to allow only radicals to flow from the inner volume into a mixing volume formed within the ground anode electrode. The mixing volume is separated from the inner volume by a gas injection ring. The radicals from the first etchant gas are mixed and reacted with a second etchant gas in molecular phase, which is introduced through the ground anode electrode into a sidewall of the gas injection ring before entering the mixing volume in an evenly distributed manner.