Gallium Ion Source Using Compound Targets and Reactive Etchants
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Solution Overview
Problem
Current gallium ion sources face challenges in producing high current density gallium ions, particularly due to the low melting temperature of elemental gallium and the inefficiency of existing gaseous precursors, which limits their application in semiconductor fabrication and focused ion beam processing.
Innovation Solution
A method and apparatus utilizing a gallium compound target with a high melting temperature, combined with a gaseous etchant species to form volatile gallium species within a plasma chamber, enhancing the sputtering yield and ionization of gallium ions in an ion source, such as an indirectly heated cathode ion source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a liquid gallium source is used in an ion source, then gallium ions can be produced, but the source cannot provide high current density over a relatively larger area due to the low melting temperature of elemental gallium
Solution Approach 1:
The patent uses composite material targets consisting of gallium compounds (such as gallium oxide, gallium nitride, gallium phosphide, or gallium arsenide) combined with other elements. These composite materials have higher melting temperatures than pure gallium while still providing sufficient gallium content for ion production, thereby enabling high current density over larger areas without the temperature limitations of elemental gallium.
2Productivity
If a solid gallium target is used in an ion source, then the target can be inserted into the ion source chamber, but the sputter yield is low because the ion energy is less than 100 eV due to the floating self bias potential on the dielectric target surface
Solution Approach 1:
The patent introduces an intermediary substance - a reactive gas (such as oxygen, nitrogen, or fluorine-containing gases) - that reacts with the gallium compound target to form volatile gallium species. This intermediary enables chemical etching that supplements physical sputtering, significantly enhancing the release of gallium atoms into the gas phase even at low ion energies below 100 eV, thereby overcoming the low sputter yield limitation.
3Productivity
If gaseous precursors are used for ion species, then the precursors can serve as a source of material for the ion source, but gaseous precursors do not exist for some ionic species or yield low beam current
Solution Approach 1:
The patent utilizes phase transitions by converting solid gallium compound targets into gaseous volatile species through chemical reactions. The reactive gas reacts with the solid target to form volatile gallium compounds that evaporate into the gas phase, providing a continuous supply of gallium atoms for ionization. This phase transition from solid to gas enables high beam current production without requiring pre-existing gaseous precursors.
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 enables the production of high current, stable gallium ion beams with a higher fraction of gallium ions, suitable for large-area semiconductor processing and ion implantation systems, by leveraging the high sputtering rate and thermal stability of gallium compounds like gallium nitride, phosphide, arsenide, and oxide, along with chemical etching to prevent unwanted deposits and maintain target composition.
Implementation Method 1
providing a source of gaseous etchant species operable to react with the gallium compound target to form a volatile gallium species
Implementation Method 2
The solid target may act as a sputtering target for the plasma ions, wherein the plasma ions are accelerated toward the target and sputter atoms or groups of atoms from the target
Implementation Method 3
a plasma may be generated using chosen ion species in the ion source chamber
Data Source
AI summary
In one embodiment, a method for generating an ion beam having gallium ions includes providing at least a portion of a gallium compound target in a plasma chamber, the gallium compound target comprising gallium and at least one additional element. The method also includes initiating a plasma in the plasma chamber using at least one gaseous species and providing a source of gaseous etchant species to react with the gallium compound target to form a volatile gallium species.