How Can Fragile Nanostructures Be Analyzed Accurately? Understanding Low-Temperature ALD Protective Coatings
As semiconductor processes continue to scale down, structures on wafers become increasingly fine. Examining these structures often requires cross-sectional sample preparation. If the sample deforms during preparation, the analysis may no longer reflect its original condition.
Preserving nanostructures during analysis is therefore an important challenge in accurate characterization.
On October 27, 2026, the National Center for Instrumentation Research (NCIR) at NIAR announced the results of its collaboration with MSS. Using atomic layer deposition (ALD) at temperatures below 100°C, the team formed nanoscale protective layers on metal oxide resist (MOR) structures following High-NA EUV lithography, helping reduce structural damage during subsequent analysis.
Why Do Nanostructures Need Protective Coatings?
Examining patterns after lithography may involve analyzing cross-sectional morphology and material interfaces as well as observing the surface. Damage to fine resist structures during sample preparation can make interpretation more difficult.
A protective coating provides additional support for the structure before analysis. By helping reduce damage from subsequent processing, it allows the analysis to more closely represent the sample’s original condition.
What Is ALD? A Technique for Coating Fine Structures Conformally
Atomic layer deposition (ALD) is a thin-film deposition technique that builds films gradually through repeated surface-reaction cycles.
The process alternately introduces precursors and reactants, with purging steps between exposures to remove residual gases. Self-limiting surface reactions and control of the number of cycles enable precise thickness control and conformal coverage over complex surfaces.
For fine structures, an important evaluation criterion is whether the film uniformly covers the areas requiring protection, alongside the film’s thickness.
Why Does Low-Temperature ALD Matter?
Coating processes must accommodate the limits of the materials being treated. For materials with restricted thermal budgets, lower-temperature deposition offers greater flexibility in process design.
Developing a low-temperature ALD process requires consideration of reaction conditions, thickness control and film quality together. In this collaboration, the technical focus was on forming a protective layer below 100°C that could support the analysis of resist structures.
This highlights the need to evaluate deposition temperature, substrate properties and the intended downstream application together when determining whether a film meets its functional requirements.
What Role Do Thin Films Play Beyond Device Manufacturing?
This case illustrates how thin-film technology can support sample protection and material analysis alongside its role in device manufacturing.
In process development, reliable analytical data helps guide decisions about materials and process adjustments. Evaluating a protective coating therefore involves considering three questions:
- Material compatibility: Can the substrate tolerate the processing temperature and chemical reaction conditions?
- Film coverage: Can the protective layer cover the fine structures requiring analysis?
- Analytical suitability: How can the protective effect be verified, and how does the coating itself affect the analysis?
As semiconductor structures continue to shrink, aligning film control, material compatibility and analytical requirements remains an important area of shared interest for surface engineering and characterization technologies.
Sources
- NCIR: NIAR and MSS Overcome a Bottleneck in Post-Lithography Structural Analysis for Next-Generation EUV Processes, October 27, 2026. Original announcement in Chinese.
- ASM: Atomic Layer Deposition. Technical background on ALD principles, thickness control and conformality.
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