TEM Sample Preparation With EBID Contrast for Fragile Topography
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Solution Overview
Problem
Existing methods for preparing TEM samples, particularly for nano-scaled structures in semiconductor processing, face challenges with protecting vulnerable structures like polymer resist lines or porous silicon, as they are prone to damage and lack sufficient contrast with conventional protective layers, and sputtering techniques are not viable.
Innovation Solution
A method involving Electron Beam Induced Deposition (EBID) is used to create a conformal contrasting layer on the substrate's topography, spaced apart from the patterned area, followed by a protective layer, ensuring the patterned features are protected and provide clear contrast for TEM analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sputtering techniques are used to deposit a contrasting layer, then the contrasting layer provides good visibility in TEM, but the vulnerable structures such as polymer resist lines or porous silicon structures are damaged
Solution Approach 1:
The patent introduces EBID deposition as an intermediary technique between the electron beam and the vulnerable structures. The electron beam induces decomposition of precursor molecules in the vapor phase, forming contrasting material only where the beam is directed, without direct mechanical or chemical interaction with the polymer structures. This mediator approach (EBID process) enables contrast enhancement while preserving structure integrity.
Solution Approach 2:
The patent replaces the mechanical sputtering process with an electron beam-induced chemical deposition process. Instead of using ion bombardment to deposit contrasting material, the method uses electron beam energy to trigger chemical reactions in vapor-phase precursors, allowing non-contact, non-damaging deposition of contrasting material that provides TEM visibility without mechanical damage to vulnerable structures.
2Reliability
If conventional protective layers are applied by spin-on, PVD, CVD, or evaporation methods, then the structures are protected during TEM preparation, but the polymeric top surface is damaged or the contrast with the protective layer is insufficient
Solution Approach 1:
The patent applies EBID deposition as a preliminary action before TEM sample preparation. By depositing the contrasting layer first through electron beam-induced decomposition of precursors, the vulnerable polymer structures are subsequently protected during FIB milling without requiring aggressive protective layer application methods that would damage the polymer surface. The contrasting layer is formed in advance with precise spatial control.
Solution Approach 2:
The patent changes the deposition parameters from conventional thermal or physical vapor deposition to electron beam-induced decomposition. This parameter change enables deposition at lower temperatures and with better spatial control, preventing polymer damage while providing sufficient contrast. The electron beam energy and precursor vapor pressure are controlled to achieve selective deposition only where needed.
3Measurement precision
If a thicker layer of contrasting material is deposited on the target area by EBID, then the conformal layer provides better contrast, but the deposition time and material usage increase
Solution Approach 1:
The patent applies EBID deposition with highly localized electron beam scanning over the target area. The contrasting material is deposited only where the electron beam is directed, creating a conformal layer with spatially varying thickness that provides sufficient contrast while minimizing total deposition time and material usage. The local quality approach ensures contrast is enhanced only where needed for TEM visualization.
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 method allows for high-quality TEM analysis by providing clear contrast and protecting vulnerable structures without damage, enabling accurate measurement and visualization of nano-scaled features.
Implementation Method 1
The local deposition is performed by Electron Beam Induced Deposition (EBID), i.e. without using a mask to cover the substrate surface outside the local target area
Data Source
Figure 1~2
Figure 3a~3b
Figure 4~5b
AI summary
A substrate (1) is provided comprising on its surface a patterned area (8) defined by a given topography. The substrate is to be processed for obtaining a TEM sample (4) in the form of a slice of the substrate . According to the method of the invention, a conformal layer (7) of contrasting material is deposited on the topography, by depositing a layer (5) of the contrasting material on a local target area (6) of the substrate, spaced apart from the patterned area (8). The material is deposited by Electron Beam Induced Deposition (EBID). The deposition parameters, the thickness of the layer (5) deposited in the target area (6), and the distance of said target area to the patterned area, are such that a conformal layer (7) of the contrasting material is formed on the topography of the patterned area (8). This is followed by the deposition of the protective layer (10), which does not damage the topography in the patterned area (8), as it is protected by the conformal layer (7). The TEM sample (4) is prepared in a manner known in the prior art, for example by FIB. The conformal contrasting layer (7) provides a good contrast with the protective layer, thereby allowing a high quality TEM analysis.