Focused Ion Beam System Mode Switching
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Solution Overview
Problem
Existing charged particle beam systems face challenges in precisely controlling the rate of material removal or deposition, often resulting in substrate damage during imaging processes, and require complex and costly setups to switch between milling and imaging modes.
Innovation Solution
A focused charged particle beam system capable of selectively operating in multiple modes, characterized by stored operating parameters, including plasma source and column settings, allowing for optimized milling and imaging processes with minimal substrate damage and rapid mode switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a focused ion beam system uses a single ion source for both milling and imaging, then device complexity is reduced, but substrate damage occurs during imaging due to high beam current
Solution Approach 1:
The system dynamically adjusts the ion beam current based on the operational mode. During imaging, the beam current is reduced to minimize substrate damage, while during milling, the beam current is increased to maximize material removal rate. This dynamic control allows a single ion source to perform both functions effectively without causing harmful effects in either mode.
Solution Approach 2:
The system changes key operating parameters (beam current, voltage, gas pressure) depending on whether milling or imaging is being performed. By adjusting these parameters, the same ion source can operate in a high-current mode for milling and a low-current mode for imaging, thus avoiding substrate damage during imaging while maintaining system simplicity.
2Object-affected harmful factors
If a focused ion beam system uses separate ion sources for milling and imaging, then substrate damage is minimized, but device complexity and cost increase
Solution Approach 1:
The patent makes a single ion source universal by enabling it to perform both milling and imaging functions. Through dynamic control of beam parameters and the use of different ion species (e.g., heavy ions like Ga+ for milling, lighter ions like H+ or He+ for imaging), one source replaces what would traditionally require two separate sources, thereby reducing device complexity and cost while still preventing substrate damage during imaging.
Solution Approach 2:
By changing parameters such as ion species mass, beam current, and energy, a single ion source can be optimized for different functions. For imaging, light ions at low current are used to minimize damage; for milling, heavy ions at high current are used to maximize etching efficiency. This parameter flexibility allows one source to replace multiple specialized sources.
3Productivity
If beam current is increased for faster milling, then productivity improves, but substrate damage increases
Solution Approach 1:
The system changes the ion species parameter to decouple milling rate from substrate damage. Heavy ions (e.g., Ga+, In+) are used for milling where high mass provides efficient sputtering at high currents. For imaging or sensitive operations, light ions (H+, He+) are used where low mass reduces damage even at comparable currents. This parameter change allows high productivity during milling without permanently increasing damage risk, as the damage can be controlled by switching ion species.
Solution Approach 2:
The beam current is dynamically adjusted based on the operational requirements. During milling operations, high current is applied to maximize material removal rate. During imaging or when approaching critical features, the current is reduced to minimize damage. This dynamic control allows the system to achieve high productivity when needed while protecting the substrate when sensitivity is required.
4Object-affected harmful factors
If beam current is reduced for imaging to minimize substrate damage, then substrate damage decreases, but imaging quality and signal-to-noise ratio worsen
Solution Approach 1:
The system changes the ion species parameter to resolve the contradiction between low damage and high image quality. Light ions (H+, He+) are used for imaging because they produce sufficient secondary electron signal even at low currents and cause minimal substrate damage. Heavy ions would produce better signal but cause excessive damage. By selecting appropriate ion species, the system achieves both low damage and acceptable imaging quality simultaneously.
Solution Approach 2:
The patent uses secondary electron detection as an intermediary mechanism to achieve good imaging quality at low beam currents. Instead of relying on high primary beam current to generate image signal, the system detects secondary electrons emitted from the substrate surface, which can be detected with high sensitivity even when the primary beam current is low. This intermediary detection method decouples image quality from beam current level.
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
Enables accurate and efficient material processing with minimal substrate damage, allowing for precise control of milling and imaging operations, reducing overall processing time and extending tool lifetime.
Implementation Method 1
A method and apparatus for providing a focused ion beam to a substrate for ion beam induced processing
Implementation Method 2
The milling process utilizes the high atomic weight and high energy of the charged particles in the beam to sputter away atoms from the substrate
Implementation Method 3
the focused charged particle beam is vectored across the surface of the substrate in a predetermined pattern. This vectoring process is accomplished by beam deflectors which generate electrostatic or magnetic dipole fields
Implementation Method 4
This vectoring process is accomplished by beam deflectors which generate electrostatic or magnetic dipole fields directed perpendicularly to the direction of beam travel
Data Source
AI summary
A method for performing milling and imaging in a focused ion beam (FIB) system employing an inductively-coupled plasma ion source, wherein two sets of FIB system operating parameters are utilized: a first set representing optimized parameters for operating the FIB system in a milling mode, and a second set representing optimized parameters for operating in an imaging mode. These operating parameters may comprise the gas pressure in the ICP source, the RF power to the ICP source, the ion extraction voltage, and in some embodiments, various parameters within the FIB system ion column, including lens voltages and the beam-defining aperture diameter. An optimized milling process provides a maximum milling rate for bulk (low spatial resolution) rapid material removal from the surface of a substrate. An optimized imaging process provides minimized material removal and higher spatial resolutions for improved imaging of the substrate area being milled.