Ion Milling Beam Control Using Oscillator Deposition Feedback
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Solution Overview
Problem
Ion milling devices face challenges in maintaining uniformity of processed shapes due to variations in ion beam output caused by changes in discharge current, ion beam current, and ion beam distribution, especially during sample replacement, which affects the reproducibility of the milling process.
Innovation Solution
An ion milling device with a control unit that adjusts the ion beam output based on the vibrational frequency change of an oscillator, which monitors the deposition of sputtered particles, ensuring the frequency change remains within a predetermined range to stabilize the ion beam output and improve processing uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If users adjust control parameters empirically based on measured values, then the device can operate with simple control, but the processing uniformity and reproducibility deteriorate
Solution Approach 1:
The patent implements real-time feedback control by monitoring the actual ion beam output and comparing it with target values, then automatically adjusting control parameters to maintain ion beam stability. This eliminates empirical adjustment and ensures consistent processing uniformity through closed-loop control.
Solution Approach 2:
The system dynamically changes control parameters (such as ion source power, gas flow rates, or beam current) based on real-time measurements of ion beam output characteristics. This automatic parameter adjustment ensures the ion beam remains within specified ranges without requiring user intervention.
2Power
If control parameters are set to obtain desired ion beam output, then the ion beam can be generated, but variations occur during milling process due to outgas adsorption, causing output instability
Solution Approach 1:
The system continuously monitors ion beam output parameters and detects variations caused by outgas adsorption on internal electrodes. Real-time feedback control automatically adjusts control parameters to compensate for these variations and maintain stable ion beam output throughout the milling process.
Solution Approach 2:
The system performs preliminary detection of ion beam output characteristics before and during the milling process. By detecting changes in advance, the control system can proactively adjust parameters to prevent output instability before it affects processing uniformity.
3Measurement precision
If etching amount is monitored by measuring mass of deposited substance on oscillator, then etching amount can be measured, but variations in central and peripheral ion beam intensity are not fully reflected
Solution Approach 1:
The patent divides the ion beam monitoring into multiple regions by placing multiple oscillators at different positions (central and peripheral regions). Each oscillator independently measures local etching amounts, allowing the system to detect and correct intensity variations between different beam regions.
Solution Approach 2:
The oscillators serve as intermediary measurement devices that directly interact with the ion beam in different regions. By using multiple oscillators as intermediaries, the system obtains accurate local measurements that reflect actual ion beam intensity variations, which are then used to adjust beam uniformity.
4Measurement precision
If mass of deposited substance is measured from resonance frequency change, then etching amount can be obtained, but correct measurement cannot be performed when deposit falls during milling process
Solution Approach 1:
The patent uses multiple oscillators positioned at different locations to measure etching amounts independently. If deposit falls on one oscillator, other oscillators continue to provide valid measurements, ensuring measurement reliability is maintained through local redundancy.
Solution Approach 2:
The system continuously monitors oscillator resonance frequencies and detects abnormal changes that indicate deposit fall. By detecting these changes in advance, the system can identify measurement errors and switch to alternative measurement data or adjust processing parameters to prevent further measurement 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
The solution stabilizes ion beam output and enhances processing reproducibility by continuously monitoring and adjusting the ion beam to maintain consistent sputtering rates, thereby ensuring uniformity of the processed sample shape.
Implementation Method 1
irradiate a sample (e.g., a metal, a semiconductor, a glass, a ceramic, and the like) to be observed by an electron microscope with an unfocused ion beam and sputter the atoms on a sample surface without stress by the sputtering phenomenon
Implementation Method 2
an ion source that emits an unfocused ion beam toward the sample
Implementation Method 3
an oscillator that is disposed in the sample chamber, and an oscillation circuit that oscillates the oscillator and outputs an oscillation signal to the control unit, in which the control unit controls the output of the ion beam such that a vibrational frequency change amount of the oscillator per unit time due to deposition of sputtered particles generated by irradiating the sample with the ion beam on the oscillator is kept within a predetermined range
Data Source
AI summary
In order to improve the processing reproducibility, an ion milling device 100 includes a sample chamber 107, a sample stage 102 that is disposed in the sample chamber on which a sample is placed, an ion source 101 that emits an unfocused ion beam toward the sample, a control unit 112 that controls an output of the ion beam, an oscillator 104 that is disposed in the sample chamber, and an oscillation circuit 111 that oscillates the oscillator and outputs an oscillation signal to the control unit, in which the control unit controls the output of the ion beam such that a vibrational frequency change amount of the oscillator per unit time due to deposition of sputtered particles generated by irradiating the sample with the ion beam on the oscillator is kept within a predetermined range.