UV-Assisted ICP Ignition for Clean High-Pressure Plasma Start
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Solution Overview
Problem
Conventional plasma processing tools face challenges in achieving reliable and efficient plasma ignition, particularly at higher gas pressures, due to issues such as arcing, localized sputtering, and slow ignition times, which can lead to contamination and reduced plasma uniformity.
Innovation Solution
The use of an ultraviolet light source to emit a beam onto the dielectric or metal surfaces within the plasma chamber, prior to or during plasma ignition, to enhance the initial exponential growth of the plasma, reducing the need for high RF power and improving ignition repeatability and reducing ion bombardment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional plasma ignition methods are used at higher gas pressures, then plasma can be sustained, but arcing and localized sputtering occur leading to contamination and reduced plasma uniformity
Solution Approach 1:
The patent applies preliminary action by introducing ultraviolet light irradiation before plasma ignition to pre-ionize the gas and generate seed electrons on the dielectric wall surface. This preliminary electron generation enables smoother plasma breakdown at higher pressures without requiring high-power RF pulses that cause arcing and sputtering, thus maintaining reliability while eliminating contamination.
Solution Approach 2:
The patent uses ultraviolet light as an intermediary to facilitate plasma ignition. The UV light acts as a mediator that converts optical energy to electron generation, which then initiates plasma formation without direct electrical discharge. This intermediary approach avoids the harmful arcing and sputtering that occur with conventional direct RF ignition methods.
2Reliability
If high RF power is used to achieve plasma ignition, then plasma can be ignited, but ignition time increases and plasma uniformity decreases
Solution Approach 1:
The system performs preliminary ionization using ultraviolet light before applying RF power. This pre-generation of electrons and ions creates favorable conditions for rapid plasma breakdown, significantly reducing the time required for ignition while maintaining reliability. The preliminary action eliminates the need for prolonged high-power RF application.
Solution Approach 2:
The patent changes the ignition approach by introducing optical energy (ultraviolet light) as an additional parameter to initiate plasma. This parameter change from purely electrical ignition to optically-assisted ignition enables faster plasma formation with lower RF power requirements, reducing both ignition time and power consumption.
3Reliability
If high RF power is applied for plasma ignition, then plasma ignition can be achieved, but ion bombardment and sputtering increase causing wall contamination
Solution Approach 1:
Ultraviolet light serves as an intermediary that enables plasma ignition through photoelectric emission and photodissociation rather than direct high-power electrical discharge. This intermediary mechanism generates electrons and reactive species without the intense ion bombardment that causes sputtering, thereby maintaining ignition capability while eliminating wall contamination.
Solution Approach 2:
The patent converts the potentially harmful effect of requiring high RF power into a benefit by using UV light to pre-ionize the gas. This conversion allows the system to use lower RF power levels for ignition, transforming the original problem of high-power-induced sputtering into an advantage of reduced contamination while maintaining reliable plasma ignition.
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 approach allows for faster and more reliable plasma ignition with reduced RF power, minimizing sputtering and contamination, and enhancing plasma uniformity and cleanliness in semiconductor processing.
Implementation Method 1
emitting an ultraviolet light beam onto a metal surface or a dielectric surface in the plasma chamber. The metal surface or the dielectric surface can emit one or more electrons into the plasma chamber when the ultraviolet light beam is incident on the metal surface or the dielectric surface
Implementation Method 2
an inductive coupling element located proximate the dielectric wall... energizing the inductive coupling element with a radio frequency (RF) energy to sustain the plasma
Implementation Method 3
a plasma chamber... energizing the inductive coupling element with a radio frequency (RF) energy to sustain the plasma in the process gas
Data Source
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AI summary
Plasma processing apparatus and associated methods are provided. In one example, a plasma processing apparatus includes a plasma chamber. The plasma processing apparatus includes a dielectric wall forming at least a portion of the plasma chamber. The plasma processing apparatus includes an inductive coupling element located proximate the dielectric wall. The plasma processing apparatus includes an ultraviolet light source configured to emit an ultraviolet light beam onto a metal surface that faces an interior volume of the plasma chamber. The plasma processing apparatus includes a controller configured to control the ultraviolet light source.