Plasma System Backside Electrode Enveloping Substrate Holder
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Solution Overview
Problem
Existing plasma systems with parallel electrodes suffer from substrate contamination due to electrode sputtering, particle generation at the showerhead, and non-uniform gas flow caused by deposition of plasma components on the showerhead apertures, leading to defects and increased processing costs.
Innovation Solution
A novel plasma configuration using a backside electrode to envelop the substrate holder electrode, eliminating direct contamination and particle deposition, and allowing a non-conductive showerhead outside the plasma region for uniform gas distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If parallel plate electrodes are used for plasma generation, then plasma processing can be performed, but substrate contamination occurs due to electrode sputtering
Solution Approach 1:
The patent inverts the traditional electrode configuration by placing the substrate holder as the top electrode and introducing a backside electrode below the substrate holder. This inversion changes the plasma generation geometry from direct parallel plate contact to a configuration where plasma is generated around and behind the substrate holder, preventing direct sputtering of the substrate while maintaining plasma processing capability
Solution Approach 2:
The electrode system is segmented into multiple components: the substrate holder electrode (top), the backside electrode (bottom), and the side electrode. This segmentation allows independent optimization of each component's function, with the backside electrode specifically designed to generate plasma that envelops the substrate holder without directly contacting the substrate, thus reducing contamination
2Manufacturing precision
If a shower head structure is used for gas distribution, then gas flow uniformity is improved, but particle generation and aperture closure occur
Solution Approach 1:
The shower head structure is extracted from the plasma region and repositioned to be located outside the plasma zone. The gas distribution apertures are positioned in an area not exposed to plasma, preventing particle generation at the shower head and avoiding aperture closure while still achieving uniform gas flow distribution to the plasma region
Solution Approach 2:
A non-conductive material is introduced as an intermediary between the gas supply system and the plasma region. This non-conductive shower head structure mediates the gas distribution function while being isolated from the plasma environment, preventing direct interaction between plasma and the gas distribution apertures
3Productivity
If the top electrode is used for gas distribution, then plasma generation is enabled, but direct sputtering contamination of the substrate occurs
Solution Approach 1:
The functional roles are inverted: the substrate holder becomes the top electrode for plasma generation, while a separate backside electrode is positioned below to provide the counter-electrode function. This inversion allows plasma generation without direct exposure of the substrate to sputtering from the top electrode, as the plasma is generated in the region between the substrate holder and the backside electrode
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 enhances process uniformity and yield, reduces defect density, and lowers processing costs by preventing substrate contamination and maintaining consistent gas flow, resulting in higher reliability and throughput.
Implementation Method 1
Two parallel conducting plates, a top plate (aa) and a bottom plate (bb) with terminals for connection (a) and (b) to the voltage supply is shown. Plasma is struck between the electrodes (aa) and (bb) using either a DC voltage, an AC (or RF) voltage or a pulsed voltage waveform applied to terminals (a) and (b).
Implementation Method 2
When a plasma (c) is lighted (initiated) the gas mixture supplied through the orifices (ee) in the second conducting electrode (aa) to the chamber is ionized, that is there are positive and negative particles that exist in the plasma (c) and depending on the applied voltages they are accelerated towards the electrodes with energy.
Implementation Method 3
The gas mixture (f) for the processing passes through the orifices or apertures (ee) of the shower head providing uniform reaction capability in the plasma chamber when plasma C is on between the electrodes (aa) and (bb).
Data Source
Figure 1
Figure 2
AI summary
A plasma system for substrate processing comprising, a conducting electrode (b,bb) on which one or more substrates (d) can be held; a second conducting electrode (a) placed adjacent but separated from the substrate holding electrode on the side away from the side where the substrates are held; and a gas mixture distribution shower head (e) placed away from the conducting electrode on the side where the substrates are held for supplying the gas mixture (f) needed for processing the substrates in a uniform manner; such that a plasma configuration initiated and established, between the con- ducting electrode holding the substrates and the second conducting electrode envelops the electrode holding the substrate, is kept away from the shower head activating and distributing the gas mixture through orifices (ee) in the shower head, there by providing advantages of uniformity, yield and reliability of process.