Ion Beam Idle Power Control for Aperture Protection
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Solution Overview
Problem
Focused ion beam systems face significant downtime and aperture damage due to the lengthy settling time required when restarting after being idle, as conventional beam blanking methods continue to generate ions that cause wear on the column components.
Innovation Solution
An automatic power control system that detects when the ion beam is idle and reduces the beam current to prevent ion milling at aperture planes, allowing for immediate restoration without extensive settling time by either extinguishing the plasma or ramping down the extraction voltage in ICP and LMIS systems, respectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the ion source is completely turned off during idle periods, then aperture damage is prevented, but the system requires lengthy settling time (up to an hour) to return to operational state
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the extraction voltage parameter. During idle periods, the extraction voltage is reduced to a low level (e.g., 100-1000V) rather than completely shutting off the ion source. This parameter adjustment prevents ion beam formation that would damage apertures while maintaining the plasma source in a state that requires minimal settling time for restoration, thus resolving the contradiction between preventing aperture damage and minimizing settling time.
2Object-affected harmful factors
If beam blanking is used to prevent ion beam from striking the sample during idle periods, then sample damage is prevented, but the ion beam continues to strike aperture plates causing wear and destruction
Solution Approach 1:
The patent extracts or removes the harmful ion beam from the system during idle periods by reducing the extraction voltage to a level below the threshold required for ion beam formation. This eliminates the ion beam entirely during idle periods, preventing it from striking both the sample (when blanked) and the aperture plates, thus resolving the contradiction between preventing sample damage and preventing aperture plate wear.
Solution Approach 2:
The patent applies preliminary action by reducing the extraction voltage before the idle period begins or at the onset of idle detection. This proactive reduction in extraction voltage prevents the formation of damaging ion beams before they can strike the aperture plates, thereby preventing aperture plate wear while maintaining sample protection during subsequent blanking operations.
3Speed
If the extraction voltage is maintained at high levels during idle periods, then the system is ready for immediate operation, but ion milling occurs at aperture planes causing component degradation
Solution Approach 1:
The patent applies dynamics by making the extraction voltage adjustable and dynamic rather than fixed. The system automatically adjusts the extraction voltage based on operational state: high voltage during operation for immediate readiness, and reduced voltage during idle periods to prevent ion milling. This dynamic adjustment resolves the contradiction between maintaining system readiness and preventing component degradation.
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 minimizes downtime and aperture damage by preventing ion flow during idle periods, enabling rapid system readiness and extending the lifespan of column components.
Implementation Method 1
inductively coupled plasma (ICP) sources have been developed which are capable of providing charged particles within a narrow energy range
Implementation Method 2
Beam blanking is typically accomplished by way of an electrostatic 'beam blanker,' which can consist of metal plates... with a small gap... where the beam passes, which will deflect the beam when a voltage... is applied to one plate
Data Source
AI summary
An improved method and apparatus for shutting down and restoring an ion beam in an ion beam system. Preferred embodiments provide a system for improved power control of a focused ion beam source, which utilizes an automatic detection of when a charged particle beam system is idle (the beam itself is not in use) and then automatically reducing the beam current to a degree where little or no ion milling occurs at any aperture plane in the ion column. Preferred embodiments include a controller operable to modify voltage to an extractor electrode and/or to reduce voltage to a source electrode when idle state of an ion source of the charged particle beam system is detected.