Single-Atom Supertip for Focused Ion Beam Stability
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Solution Overview
Problem
Current focused ion beam devices face limitations in achieving stable sub-nanometer spot sizes due to emitter tip instability and competing ion beams, which affect measurement accuracy and precision in CD and DR applications.
Innovation Solution
A focused ion beam system with a gas field ion source featuring a single-atom supertip on a single crystal base tip, along with a control loop for beam current stabilization and sample charge management, to ensure precise and stable ion beam generation and measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gas field ion source with a conventional emitter tip is used, then ion beam generation is achieved, but the probe current stability deteriorates due to emitter tip instability and competing ion beams
Solution Approach 1:
The emitter tip is segmented into a base tip and a supertip, where the base tip provides structural support and the supertip (single-atom tip) provides stable ion emission. This segmentation allows the emission function to be separated from the support function, improving probe current stability by isolating the emission source to a single atom that does not suffer from competing emission sites.
Solution Approach 2:
The supertip is designed with a specific local quality - a single atom at its apex - that differs from the base tip structure. This local single-atom configuration creates a unique electric field distribution that eliminates competing ion beams and ensures stable, reproducible ion emission, directly addressing the probe current stability issue.
2Measurement precision
If the spot size is reduced to sub-nanometer range, then measurement precision is improved, but beam stability deteriorates due to emitter tip instability
Solution Approach 1:
By segmenting the emitter into base tip and supertip, the system achieves both small spot size (through the sharp supertip) and beam stability (through the stable single-atom emission). The segmentation allows independent optimization of emission sharpness and emission stability.
Solution Approach 2:
The emitter tip geometry is changed to a single-atom supertip configuration, which fundamentally alters the electric field distribution and ion emission characteristics. This parameter change enables simultaneous achievement of sub-nanometer spot size and stable beam current by eliminating the competing emission sites that plague conventional emitters.
3Quantity of substance
If multiple emission centers exist on the emitter tip, then ion beam current is increased, but measurement accuracy deteriorates due to competing ion beams
Solution Approach 1:
The invention extracts the emission function to a single atom at the supertip apex, removing all other potential emission centers. This extraction of the emission function to a single location eliminates competing ion beams while maintaining sufficient ion current for measurements, as the single atom provides a focused, stable emission source.
Solution Approach 2:
The local quality of the supertip - having exactly one atom at its apex - creates a unique emission characteristic where all ions originate from a single, well-defined location. This local single-center emission provides both sufficient current and high measurement accuracy by eliminating the spatial and temporal variations introduced by multiple competing emission centers.
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 system achieves improved probe current stability and measurement accuracy, enabling spot sizes below 0.1 nm with less than 2% current variation, enhancing the precision of CD and DR measurements.
Implementation Method 1
a voltage is supplied to an emitter in the presence of an operation gas. Therefore, particles like ions of the operation gas are emitted from an emitter tip
Implementation Method 2
a detector for detection of backscattered and/or secondary particles released from the specimen
Data Source
AI summary
A focused ion beam device is described comprising a gas field ion source with an analyzer for analyzing and classifying the structure of a specimen, a controller for controlling and/or modifying the structure of the specimen according to the analysis of the analyzer, an emitter tip, the emitter tip has a base tip comprising a first material and a supertip comprising a material different from the first material, wherein the supertip is a single atom tip and the base tip is a single crystal base tip. Furthermore, the focused ion beam device has a probe current control and a sample charge control. A method of operating a focused ion beam device is provided comprising applying a voltage between a single emission center of the supertip and an electrode, supplying gas to the emitter tip, analyzing and classifying the structure of a specimen, and controlling the structure of the specimen.