Sonic AFM creates first in-line semiconductor subsurface metrology system

Sonic AFM creates first in-line semiconductor subsurface metrology system

Technology News |
By Nick Flaherty

Dutch semiconductor equipment maker Nearfield Instruments has developed the industry’s only in-line, non-destructive subsurface metrology system using a combination of sound waves and atomic force microscopy (AFM).

The Audira system combines an acoustic microscopy technique with its own proprietary AFM technology. The AFM probe is used to ‘listen’ to the sound waves coming through the wafer layers. The wave interacts with all the transitions and surfaces within the device and reflects information back. The pattern of that reflected wave and the time of arrival contains data about the structure below the surface.

The system scans across the die, with each step as small as several tenths of a nanometre. The data is then translated into a comprehensive pattern of the underlying layers that provides measurement of subsurface features.

This provides highly accurate and reproducible nanometre-level measurements of buried features and defects, such as voids, in advanced memory and logic devices.

Audira can also measure shallow features through the surface. Using the AFM probe, surface elasticity variations can be quickly measured to reveal details about the structure below. Nearfield Instruments works with customers to develop a recipe for when to use acoustics and at what frequency, for which layers local elasticity measurements are best, and when to switch to wave propagation schemes.

“Audira is a game-changer for advanced semiconductor manufacturing. It provides measurement data that was previously not available without having to remove the wafer from the line,” said Hamed Sadeghian, CEO of Nearfield in Rotterdam.

He sees the system being used alongside transmission electron microscopy (TEM) and critical dimension-scanning electron microscopy (CD-SEM) for subsurface process control measurements. Audira uses an acoustic approach that is fast, very precise and non-destructive with the added advantages of being in-line with a fast turn-around time alongside the AFM.

“Most importantly, the Audira gives process engineers insight into the wafer’s innermost layers – details they never were able to measure before nondestructively and sometimes would never have even known to look for. Audira, like our first product Quadra, turns in-line metrology and inspection into an added value in the semiconductor manufacturing process,” he said.

Quadra uses a miniaturized AFM head architecture combined with feedforward trajectory planner (FFTP) imaging technology to enable on-device, non-destructive measurements for in-line process monitoring of very high-aspect ratio structures as well as hybrid bonding and EUV resist critical dimension metrology. This shows 100x improvement in imaging acquisition time when benchmarked against existing state-of-the-art AFM systems.

Audira is available for ordering now and the first systems will ship in Q2 2024 to top semiconductor fabs worldwide.

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