TEM Sample Preparation for Scratch-Free Deep Trench FIB Cutting
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Solution Overview
Problem
The existing methods for preparing TEM samples using Focused Ion Beam (FIB) often result in ion beam scratches, especially when dealing with deep trench structures, which can damage the sample and affect imaging quality.
Innovation Solution
A method involving the formation of a first protective layer that does not fully fill the deep trench, followed by initial FIB cutting to expose the via, subsequent side filling with a second material layer, and final FIB cutting to achieve the target thickness, thereby eliminating ion beam scratches during the sample preparation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If FIB cutting is performed directly on deep trench structures, then sample preparation can be completed in fewer steps, but ion beam scratches are produced affecting imaging quality
Solution Approach 1:
The method applies preliminary protective actions by forming a first protective layer before FIB cutting, and a second protective layer after initial cutting. This preliminary protection prevents ion beam scratches during subsequent cutting operations, resolving the contradiction between preparation efficiency and imaging quality.
Solution Approach 2:
The sample preparation process is segmented into multiple stages: initial FIB cutting to expose the via, then side filling with second material layer, followed by final FIB cutting. This segmentation allows protective layers to be applied at critical moments, preventing scratches while maintaining overall process efficiency.
2Object-affected harmful factors
If the protective layer fully fills the deep trench, then ion beam scratches are prevented, but the aspect ratio requirement cannot be met and via formation is affected
Solution Approach 1:
The solution applies different filling strategies to different regions and stages: the first protective layer partially fills the trench to maintain aspect ratio, while the second protective layer completely fills the exposed via after initial cutting. This localized quality approach prevents scratches without compromising trench structural requirements.
Solution Approach 2:
The first protective layer is applied preliminarily to provide partial protection during initial cutting. Then the via is exposed through controlled cutting, and the second protective layer is applied to complete the filling. This preliminary action sequence achieves both scratch prevention and precise trench filling.
3Manufacturing precision
If multiple FIB cutting steps are performed, then ion beam scratches are eliminated, but the preparation time increases
Solution Approach 1:
The method skips the intermediate step of manually removing and reapplying protective layers by using side filling technology. The second protective layer is directly deposited onto the exposed via surfaces through lateral deposition, rushing through what would otherwise be a time-consuming removal and reapplication process.
Solution Approach 2:
The mechanical process of removing and reapplying protective layers is replaced by a deposition-based side filling process. The second protective layer is deposited laterally onto the via surfaces, substituting mechanical manipulation with a more efficient deposition mechanism that reduces preparation time.
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 reduces or eliminates ion beam scratches, improving the quality and success rate of TEM sample preparation by ensuring the deep trench is fully filled before the final cutting step, thus preventing damage and enhancing imaging quality.
Implementation Method 1
performing, using a FIB, the first time of front and rear side cutting of a target area on the chip sample
Implementation Method 2
forming a second material layer, the second material layer fully filling the exposed via from the front side and the rear side of the TEM sample
Data Source
AI summary
The present application discloses a method for preparing a TEM sample, comprising: step 1, forming a first protective layer to non-full fill a deep trench; step 2, performing a first time of front and rear side cutting using a FIB, so as to form the TEM sample having a first thickness, and a via in the deep trench is exposed from the front side and the rear side of the TEM sample; step 3, forming a second material layer, which fully fills the exposed via from the front side and the rear side of the TEM sample; and step 4, performing a second time of front and rear side cutting of a target area on the chip sample using the FIB, so as to reduce the thickness of the TEM sample to a target thickness.