Follow Bruker and explore the latest applications of AFM in the semiconductor industry with a panel of experts.
What are the recommended cantilevers for measuring the mechanical properties of semiconductors with high modulus, such as 200 GPa?
We propose using Bruker’s sharp, high-performance cantilevers, such as the HPI Super Sharp probes, to measure mechanical parameters, particularly for materials with a high modulus of 200 GPa.
These probes are very useful when working with hard materials since they have great spatial resolution and maintain reproducibility after multiple readings. Using these cantilevers assures accurate measurement of both roughness and mechanical characteristics, with no tip wear impacting your results.
How does the Deep Trench mode differ from regular scanning modes in atomic force microscopy?
Deep Trench mode (DTMode) differs from standard scanning modes like tapping or TrueSense. While standard modes scan the surface constantly, DTMode is specially designed for structures with high aspect ratios, such as pits and vias.
It uses an adaptive step-and-settle scanning approach, resulting in more control and precision when exploring these complex features. This enables us to obtain accurate depth measurements, even at the bottom of trenches, which would be difficult with traditional modes because they lack adaptive scanning for complicated geometries.
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When should you use tapping mode over TrueSense mode in AFM, and what are the key differences between the two?
Tapping mode remains a popular approach for many AFM applications, especially when working with bigger, flatter objects or after procedures like chemical mechanical planarization (CMP). Tapping mode is particularly effective in reducing lateral stresses on the sample, making it excellent for structures that are reasonably stable and flat.
TrueSense, our enhanced version of PeakForce Tapping for automated AFM, is the preferred choice for the majority of automated procedures. Its ease of use comes from lowering parameter complexity, making it more usable in high-throughput fabrication situations.
What are the challenges and strengths of AFM’s electrical modes compared to bulk techniques?
One of the most difficult issues with AFM’s electrical modes is their susceptibility to external conditions like temperature or humidity, which can impair measurement precision at the nanoscale. However, the benefits significantly exceed these drawbacks.
AFM provides localized, high-resolution measurements that bulk methods cannot match. You obtain direct spatial information at the nanoscale, which is critical for analyzing properties such as surface charge or resistivity that can fluctuate even over small regions.
The precise mechanical control and image resolution are unparalleled, enabling AFM to execute jobs that bulk methods are unsuitable for.
What are the main application areas for atomic force microscopy in the semiconductor industry?
AFM is critical in numerous major aspects of semiconductor manufacturing. One of the most important uses is in films, where AFM can be used to evaluate roughness with sub-angstrom accuracy.
It is also widely used in lithography to measure sidewall roughness, line edge roughness, and resist depth. In etch procedures, DTMode is used extensively to measure trench depths.
Finally, CMP depends largely on AFM to monitor dishing and erosion across vast scan regions. AFM is also utilized for defect assessment and yield control, where accurate topographic imaging aids in identifying and categorizing faults.
What are some key innovations that enabled AFM to be used in a fabrication environment for semiconductor manufacturing?
Several advancements have made AFM more suitable for fabrication. First, Bruker’s high-precision CD scanners transformed metrology by delivering consistent, highly repeatable results.
These scanners can run for lengthy periods with low drift, as demonstrated by our year-long step height measurements, which had a three-sigma variance of only 15 angstroms.
Automation made it easier to integrate AFM into semiconductor fabs, providing for reliable, high-throughput measurements. Automated probe exchange, KLARF integration for defect analysis, and adaptable scan modes have greatly improved AFM’s accessibility in high-volume production situations.
What are the advantages of automated probe exchange in an AFM system, and how does it ensure good probe quality during measurements?
Automated probe exchange is a major game-changer, particularly in high-throughput fabrication environments. It provides for constant probing quality while considerably reducing downtime. If a probe becomes worn or damaged, the system will replace it automatically, guaranteeing that measurements are correct without the need for operator intervention.
This reduces human error and ensures that the AFM produces consistent, high-quality findings. We also cycle through what we call a “golden wafer” regularly to guarantee that the system’s calibration is maintained, enhancing overall measurement stability.
What role does AFM play in hybrid bonding technology, and how does it support multi-wafer thickness measurements?
Hybrid bonding is one of the most advanced semiconductor production processes, enabling chip stacking and wafer-on-wafer bonding. AFM is very useful here when dealing with many wafer thicknesses.
Our AFM systems, notably the InSight AFP platform, are intended to measure wafer thicknesses ranging from thinner wafers of 350 µm to triple wafer stacks. This is necessary to ensure the quality of the bonding process since the dimensional correctness of individual copper pads or other bonding parts is vital to the overall performance of the finished product.
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About the Speakers
Peter De Wolf is director for AFM technology & application development at Bruker Nano Surfaces, covering all applications related to Scanning Probe Microscopy (SPM). He obtained his PhD from IMEC, Belgium on the development of new SPM methods for 2D carrier profiling in semiconductors and has more than 25 years of experience on SPM. He is the author and co-author of over 30 publications related to electrical characterization using SPM. He also owns several SPM patents, and developed several new SPM modes for electrical characterization.
Sean Hand is a Senior Staff Applications Scientist with Bruker's Automated AFM group focused on the application of AFM to semiconductor manufacturing. Sean has an M.S. in physics from the University of Vermont where he focused on Atomic Force Microscopy of lipid bilayers for transdermal drug delivery. Sean has over 25 years of experience in AFM for semiconductor manufacturing and has co-authored over 20 papers and owns several patents related to Automated AFM in semiconductor manufacturing.
This information has been sourced, reviewed, and adapted from materials provided by Bruker Nano Surfaces and Metrology.
For more information on this source, please visit Bruker Nano Surfaces and Metrology.
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