Inductively Coupled Plasma Ion Source with Tunable RF Power
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Solution Overview
Problem
Conventional plasma ion sources face challenges in providing efficient RF power, achieving optimal magnetic filtering, and maintaining high voltage stability, especially when dealing with varying plasma impedance due to gas pressure and composition, which limits their effectiveness in applications like FIB tools and SIMS instruments.
Innovation Solution
The solution involves a variable frequency RF power supply with a matching network using fixed capacitors, a magnetic circuit design with high permeability to channel magnetic flux across a high voltage gap, and a gas feed insulator with a serpentine path to minimize electric field exposure and prevent breakdown, enabling efficient RF power coupling and magnetic filtering while maintaining high voltage isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional RF power supply with fixed frequency is used, then the impedance matching is simple, but the power delivery efficiency decreases when plasma impedance varies with gas pressure and composition
Solution Approach 1:
The patent implements a variable frequency RF power supply that dynamically adjusts the operating frequency to track the plasma impedance changes caused by variations in gas pressure and composition. This dynamic adjustment maintains optimal power coupling efficiency without requiring complex impedance matching networks, as the frequency tuning automatically compensates for plasma load variations.
Solution Approach 2:
The system changes the RF frequency parameter in response to plasma impedance variations. By monitoring plasma conditions and adjusting the operating frequency accordingly, the system maintains efficient power transfer despite changes in gas pressure and composition, avoiding the need for complex mechanical impedance matching devices.
2Manufacturing precision
If a magnetic circuit is placed across a high voltage gap to provide magnetic filtering, then the ion beam quality improves, but the risk of electrical breakdown increases
Solution Approach 1:
The patent introduces a dielectric material as an intermediary between the magnetic circuit and the high voltage plasma chamber. This dielectric barrier allows the magnetic field to pass through while preventing direct electrical contact, thereby eliminating the risk of breakdown while maintaining the magnetic filtering function for improved ion beam quality.
Solution Approach 2:
The dielectric barrier acts as a sacrificial protective element that can withstand high electric fields without breaking down. It provides a simple, reliable solution that protects the magnetic circuit from high voltage while maintaining system reliability, replacing the need for complex high voltage isolation designs.
3Ease of operation
If gas is fed directly into a high voltage biased chamber, then the gas flow control is simple, but high voltage breakdown through the gas line occurs
Solution Approach 1:
The patent employs a dielectric insulator as an intermediary in the gas feed line that provides electrical isolation between the ground potential gas supply and the high voltage biased chamber. This dielectric barrier allows gas to flow through while preventing electrical breakdown, maintaining both operational simplicity and high voltage reliability.
4Manufacturing precision
If an inductively coupled plasma source is used to achieve high brightness and low energy spread, then the ion beam quality improves, but the complexity of providing RF power and magnetic filtering increases
Solution Approach 1:
The patent combines the RF antenna and magnetic circuit into a single integrated structure that performs both functions simultaneously. The variable frequency RF power supply tunes the combined antenna-circuit system to resonate at the plasma frequency, achieving efficient power coupling and optimal magnetic field generation without requiring separate complex systems for each function.
Solution Approach 2:
The integrated antenna-magnetic circuit structure serves multiple functions: it provides inductive RF power coupling to the plasma and simultaneously generates the magnetic field required for ion beam extraction and filtering. This multi-functional design reduces overall system complexity while maintaining high ion beam quality.
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 improved RF power delivery, enhanced magnetic filtering, and stable high voltage operation, leading to more efficient ion beam generation and extraction with reduced thermal issues and increased operational reliability.
Implementation Method 1
induction coil adjacent to a reactor chamber for inductively coupling power into the plasma from a radio frequency power source
Implementation Method 2
the impedance between the RF power source and the plasma ion source is matched by tuning the RF frequency rather than adjusting the capacitance of the matching network
Implementation Method 3
a magnetic circuit design with high permeability to channel magnetic flux across a high voltage gap
Implementation Method 4
enhanced magnetic filtering
Implementation Method 5
a gas feed insulator with a serpentine path to minimize electric field exposure and prevent breakdown
Implementation Method 6
inductively coupled plasma ion source
Implementation Method 7
an ion beam is extracted from a small aperture and is accelerated through a bias voltage to produce a fine beam of energetic ions
Data Source
AI summary
In a plasma ion source having an induction coil adjacent to a reactor chamber for inductively coupling power into the plasma from a radio frequency power source and designed for negative and positive ion extraction, a method for operating the source according to the invention comprises providing radio frequency power to the induction coil with a RF amplifier operating with a variable frequency connected to a matching network mainly comprised of fixed value capacitors. In this device, the impedance between the RF power source and the plasma ion source is matched by tuning the RF frequency rather than adjusting the capacitance of the matching network. An option to use a RF power source utilizing lateral diffused metal oxide semiconductor field effect transistor based amplifiers is disclosed.