Multimode Ion Source for Low-Energy Molecular Ion Implantation
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Solution Overview
Problem
Conventional ion implanters are inefficient at low energies due to space charge limitations, leading to reduced ion current density and beam loss, and are incompatible with the production of large molecular ions like carborane, resulting in performance degradation and short lifetime.
Innovation Solution
A multimode ion source that operates in both arc-discharge and RF modes, with an RF power supply and matching network, allowing for the generation of plasmas based on various boron and other species, and featuring additional electrodes for increased electrode area and power density, enabling efficient molecular ion implantation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional ion implanters operate at high energies, then ion current density is maintained, but efficiency at low energies deteriorates due to space charge limitations
Solution Approach 1:
The ion source operates in two distinct modes (arc mode and RF mode) that can be dynamically switched based on the required implantation energy. Arc mode is used for high energy operations while RF mode is used for low energy operations, allowing the system to adapt its operating characteristics to match the specific application requirements and avoid space charge limitations
Solution Approach 2:
The patent changes the fundamental operating parameters of the ion source by switching between arc discharge mode (high current, high temperature) and RF mode (lower current, lower temperature). This parameter change allows the system to maintain optimal performance across different energy ranges, particularly enabling efficient low-energy implantation without suffering from space charge effects
2Quantity of substance
If arc mode is used for high current ion implantation, then ion current density is improved, but molecular ion production (e.g., carborane) deteriorates due to excessive heat
Solution Approach 1:
The system dynamically selects between arc mode and RF mode based on the type of ions required. For molecular ions like carborane, RF mode is selected to preserve molecular integrity. For applications requiring high ion current density, arc mode is selected. This dynamic selection resolves the contradiction between current density and molecular stability
Solution Approach 2:
The patent changes the temperature and power delivery parameters by switching from arc mode (high temperature, direct current) to RF mode (controlled temperature, radio frequency power). This parameter change enables the production of molecular ions without excessive heating that would cause decomposition, while still providing sufficient ion current for practical implantation
3Power
If additional electrodes are added to increase electrode area, then power density and plasma generation are improved, but device complexity increases
Solution Approach 1:
The additional electrodes in the RF mode ion source serve multiple functions: they act as both RF power delivery electrodes and plasma generation electrodes. The first pair of electrodes delivers RF power while the second pair generates plasma, but all electrodes work together to create the optimized plasma field. This multi-functionality justifies the added structural complexity by providing enhanced power density and improved molecular ion production capability
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 multimode ion source enhances molecular ion implantation efficiency and ion source performance, achieving higher plasma densities and longer lifetimes by switching between modes, thereby improving wafer throughput and dopant concentration.
Implementation Method 1
An RF power supply and matching network are provided.
Implementation Method 2
a first mode is an arc-discharge mode
Implementation Method 3
The high current may heat the tungsten filament 204 to cause thermionic emission of electrons
Implementation Method 4
The high current may heat the tungsten filament 204 to cause thermionic emission of electrons
Implementation Method 5
A second power supply 210 may bias the cathode 206 at a much higher potential than the tungsten filament 204 to cause the emitted electrons to accelerate towards and heat the cathode 206
Implementation Method 6
A source magnet (not shown) may create a magnetic field B inside the arc chamber 202 to confine the energetic electrons
Implementation Method 7
a repeller 216 at the other end of the arc chamber 202 may be biased at a same or similar potential as the cathode 206 to repel the energetic electrons
Implementation Method 8
An extraction electrode (not shown) may then extract ions 22 from the plasma 20 through an extraction aperture 220 for use in the ion implanter 100
Data Source
AI summary
Techniques for providing a multimode ion source are disclosed. In one particular exemplary embodiment, the techniques may be realized as an apparatus for ion implantation comprising an ion source that operates in multiple modes such that a first mode is an arc-discharge mode and a second mode is an RF mode.