Cryogenic FIB Sample Attachment Without Gas Deposition
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Solution Overview
Problem
Current methods for preparing transmission electron microscopy (TEM) specimens using focused ion beam (FIB) systems face challenges such as contamination from gas-assisted material deposition, mechanical stress from force-fit attachment, and time-consuming tilting processes, which affect sample preparation efficiency and accuracy.
Innovation Solution
The method involves milling asymmetric trenches with a three-dimensional depth profile to facilitate mechanical removal of pre-lamella samples without tilting the stage, and using gas-less redeposition techniques to attach the samples to a substrate or carrier grid, eliminating the need for gas-assisted deposition and reducing preparation time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If gas-assisted material deposition is used to attach the specimen to the transport tool, then the attachment strength is improved, but contamination of the FIB system chamber and samples occurs
Solution Approach 1:
The patent extracts and eliminates the gas-assisted deposition process from the FIB system chamber. By using a lift-out tool that mechanically removes the specimen and transfers it to a carrier grid outside the chamber, the harmful gas deposition step is completely removed, preventing contamination while maintaining secure attachment through mechanical means
Solution Approach 2:
The patent replaces the chemical/gas-based deposition mechanism with a purely mechanical lift-out system. The specimen is attached to the lift-out tool through mechanical engagement, then physically transferred and attached to the carrier grid through mechanical forces, substituting the contaminated gas-assisted process with clean mechanical operations
2Ease of operation
If the stage is tilted to facilitate specimen removal, then the ease of operation is improved, but the preparation time increases
Solution Approach 1:
The patent performs preliminary actions by pre-configuring the lift-out tool with the carrier grid and preparing the mechanical engagement interfaces before the specimen removal process begins. This pre-preparation eliminates the need for time-consuming stage tilting and reconfiguration during the actual removal operation
Solution Approach 2:
The patent replaces the complex stage tilting mechanism with a simpler mechanical lift-out system that operates with the stage in a fixed position. The specimen is engaged and removed through vertical lifting motions rather than requiring angular stage adjustments, significantly reducing preparation time while maintaining ease of operation
3Strength
If force-fit attachment is used to secure the specimen to the carrier grid, then the attachment strength is improved, but mechanical stress and potential damage to the specimen occur
Solution Approach 1:
The patent introduces an intermediary mechanism between the specimen and the carrier grid attachment point. Rather than direct force-fit engagement, the specimen is first secured to the lift-out tool, then transferred to the grid through a controlled intermediate step that distributes mechanical stresses and prevents direct impact forces on the fragile specimen
Solution Approach 2:
The patent implements beforehand cushioning by designing the transfer mechanism to absorb and dissipate mechanical energies before they reach the specimen. The intermediary transfer process includes stress-distributing features that prevent concentrated forces from damaging the specimen during attachment to the carrier grid
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 contamination, reduces mechanical stress, and significantly decreases the time required for sample preparation, enhancing the efficiency and accuracy of TEM specimen production.
Implementation Method 1
milling a first trench into a surface of a material; milling a second trench into the surface of the material
Implementation Method 2
using gas-less redeposition techniques to attach the samples to a substrate or carrier grid
Data Source
AI summary
A method for attaching a prepared sample to a carrier in a focused ion beam chamber. The method includes reducing a temperature within the chamber to substantially below room temperature followed by moving the prepared sample adjacent to a substrate carrier surface. The temperature can be lowered sufficiently to establish a cryogenic condition in the chamber. Attachment of the prepared sample to the substrate carrier is done by controlling the focused ion beam to raster a target area of the surface in the absence of a gas deposition precursor, to sputter material onto the base of the sample and the substrate carrier surface, thereby binding the prepared sample to the substrate carrier.