NXT’s Helios systems use non-destructive optical measurements to assess individual layers and multilayer stacks
Helios-r8 targets doped poly-Si layers on the rear side of TOPCon wafers, while Helios-tn covers SiNx, SiOxNy, TCO, and poly-Si layers
Inline measurement systems provide process data for monitoring layer uniformity and identifying deviations during production
At REI 2026, Germany-based NXT presented spectrometric tools that measure the thickness and refractive index of deposited layers, including poly-Si, SiNx, and SiOx, on TOPCon, PERC, and HJT wafers.
The company showcased its two laboratory tools, Helios-r8 and Helios-tn, with different measurement configurations and applications. The measurement is optical and non-destructive. These tools use optical reflectance spectroscopy to determine the thickness and optical constants (n and k) of both individual layers and multilayer stacks.
Helios-r8 measures the thickness and refractive index of doped poly-Si layers deposited on the etched rear side of TOPCon wafers. Its multi-angle optical configuration reduces sensitivity to wafer rotation, tilt, and surface roughness, which can otherwise influence measurements. According to NXT, Helios-r8 can complete a measurement in 200 ms or less per point.
The company offers Helios-tn to measure SiNx, silicon oxynitride (SiOxNy), transparent conductive oxide (TCO), and poly-Si layers. It can measure individual layers and the total stack on either the front or rear side of a wafer. Its tilting optics accommodate different surface conditions, including textured, etched, and polished surfaces.
NXT also offers inline tools for production lines. For process monitoring, measurements can be taken at multiple points on a wafer and across wafers collected from different positions in a deposition boat. Comparing these results helps assess layer uniformity and identify variations during a deposition run. The data can also support statistical process control (SPC), helping manufacturers identify process deviations and maintain consistent deposition conditions. These measurements let manufacturers monitor deposited-layer properties closer to the process step, rather than relying only on downstream cell performance measurements.
