TEM Sample Preparation via Inverted Focused Ion Beam Etching
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Solution Overview
Problem
In preparing TEM samples with thin film portions of 50 nm or less, the existing focused ion beam method often results in curvature due to internal stress, which is exacerbated by forming slits to release stress, making accurate observation challenging as device sizes and defect sizes decrease.
Innovation Solution
The method involves placing the thin sample on a holder with the first side surface closer to the observation target opposed to the focused ion beam column, setting the etching region adjacent to the thin film portion, and performing etching from this surface to minimize the etching amount and prevent curvature by maintaining support from unetched areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If etching processing is performed from the second side surface (farther from observation target) to reduce thin film thickness to 50 nm or less, then the thin film portion can achieve the required thickness for TEM observation, but the thin film portion becomes curved due to internal stress and insufficient support
Solution Approach 1:
The patent inverts the conventional etching approach by performing etching from the first side surface (closer to observation target) instead of from the second side surface (farther from target). This inversion allows the thin film portion to be supported by unetched regions on the first side surface, preventing curvature while achieving the required thickness reduction to 50 nm or less for TEM observation.
Solution Approach 2:
The patent applies preliminary action by performing etching from the first side surface before the thin film portion becomes fully unsupported. By removing material from the side closer to the observation target first, the method maintains structural support during the thinning process, preventing stress-induced curvature that would occur if etching were performed from the opposite side.
2Stress or pressure
If a slit is formed in the curved portion to release stress, then the thin film portion can be relieved from internal stress, but the curvature problem persists and accurate observation of small device structures becomes difficult
Solution Approach 1:
The patent applies preliminary anti-action by preventing curvature formation through the inverted etching approach, thereby preemptively avoiding the need for stress relief measures such as slit formation. By maintaining proper support during etching from the first side surface, the method eliminates the root cause of stress accumulation before it can manifest as curvature requiring intervention.
3Length of moving object
If the thin film thickness is reduced to 50 nm or less to observe smaller device structures and defects, then the observation target can be accurately imaged, but the thin film portion becomes increasingly susceptible to curvature and stress
Solution Approach 1:
The patent inverts the etching direction to work from the first side surface (closer to observation target) toward the second side surface. This inversion maintains structural support during the thinning process, enabling achievement of 50 nm or less thickness while preventing the instability and curvature that would otherwise occur in such ultra-thin films.
Solution Approach 2:
The patent changes the etching parameter (direction of material removal) to optimize the thinning process. By etching from the first side surface rather than the second, the method achieves the required thickness reduction to 50 nm or less while maintaining film stability through continuous support from unetched regions on the first side surface.
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 allows for the preparation of TEM samples with thin film portions that are not curved, even at small thicknesses, by reducing the etching amount and maintaining structural support, thus enabling accurate TEM observation without interrupting the electron beam path.
Implementation Method 1
performing the etching processing to a portion of the thin sample extending from the first side surface thereof to a front surface thereof by irradiating the processing region with the focused ion beam from the focused ion beam column
Data Source
AI summary
A TEM sample preparation method including: placing a thin sample on a sample holder so that a first side surface of the thin sample which is closer to a desired observation target is opposed to a focused ion beam column; setting a processing region, which is to be subjected to etching processing by a focused ion beam so as to form a thin film portion including the observation target and having a thickness direction substantially parallel to a thickness direction of the thin sample, to a region of the first side surface that is adjacent to the thin film portion; and performing the etching processing to a portion of the thin sample extending from the first side surface thereof to a front surface thereof by irradiating the processing region with the focused ion beam from the focused ion beam column.