Inductively Coupled Plasma Ion Source with Mass Filter for Focused Ion Beam
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Solution Overview
Problem
Current focused ion beam (FIB) systems face limitations in rapidly switching between different ion species due to slow gas exchange times in plasma ion sources and the limitations of liquid metal ion sources, which restrict high-resolution processing and versatility in applications.
Innovation Solution
An inductively coupled plasma (ICP) ion source combined with a mass filter, allowing for the selection of multiple ion species from a mixed gas plasma, enabling rapid switching between ion species by adjusting the mass filter configuration, thereby providing high-resolution beams with a wide range of mass and current choices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a liquid metal ion source (LMIS) is used to achieve high resolution processing, then spot size is reduced to 5-7 nanometers, but beam current is limited to low levels resulting in low etch rates and longer processing times
Solution Approach 1:
The patent changes the fundamental parameters of the ion source by transitioning from liquid metal to plasma-based ion generation. This enables simultaneous achievement of high beam current (milliampere to microampere range) and small spot size (micron to sub-micron range) through plasma confinement and extraction techniques, resolving the trade-off between resolution and productivity
Solution Approach 2:
The patent replaces the mechanical liquid metal source system with an inductively coupled plasma system that uses electromagnetic fields to generate and control ions. This substitution enables higher beam currents while maintaining small spot sizes through magnetic confinement and electrostatic extraction, eliminating the fundamental limitations of LMIS
2Adaptability or versatility
If a mass filter is used to select specific ion species from plasma, then ion species selectability is improved, but beam energy spread increases causing chromatic aberration and reduced resolution
Solution Approach 1:
The patent performs preliminary energy selection by extracting ions with similar energies from the plasma source before mass separation. The extraction process inherently filters ions based on their energy, creating a pre-selected beam that reduces chromatic aberration when subsequently mass-filtered, thereby maintaining higher resolution
Solution Approach 2:
The patent uses dynamic control of electric and magnetic fields in the mass filter to selectively transmit ions of specific masses while maintaining tight energy filtering. By dynamically adjusting field strengths and configurations, the system achieves both mass selectability and energy resolution, minimizing chromatic aberration
3Adaptability or versatility
If different ion species are used for different applications, then application versatility is improved, but source replacement time increases due to removal and preparation procedures
Solution Approach 1:
The patent creates a universal plasma ion source that can generate multiple ion species (gallium, indium, tin, and other metals) through plasma decomposition of their respective compounds. This single multi-functional source eliminates the need for physical source replacement, allowing rapid switching between ion species by simply changing the plasma generation parameters and precursor material
Solution Approach 2:
The patent introduces plasma as an intermediary medium that enables flexible ion species selection. Instead of directly using liquid metal sources for each ion type, the plasma process acts as a mediator that can generate various metal ions from their compounds, allowing rapid ion species switching without source replacement by simply changing plasma conditions
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 combination enables rapid switching between ion species in less than a minute, achieving high-resolution processing with spot sizes less than 1 micron and beam currents between 1 pA and 10 μA, enhancing the versatility and efficiency of FIB systems for various applications.
Implementation Method 1
inductively coupled plasma (ICP) ion source
Implementation Method 2
The ion species that comprises the focused beam is selected from the multiple ion species leaving the source using a mass filter
Data Source
AI summary
An inductively coupled plasma source having multiple gases in the plasma chamber provides multiple ion species to a focusing column. A mass filter allows for selection of a specific ion species and rapid changing from one species to another.