HELios LAB-tn

Coating Measurement of Solar Cells

Thickness and Refractive Index of Silicon Nitride

For wafer based solar cells the anti-reflective coating, surface passivation and diffusion barrier play an important role to achieve high solar cell efficiency and long term stability. Because of its excellent characteristics Silicon Nitride coating (a-SiNx:H) is widely used for this purpose. Process parameters like gas pressure and temperature of the cell during deposition have a strong influence on the layer thickness, colour and the optical constants n&k of Silicon Nitride. Traditionally it takes time and skills to obtain a precise coating distribution map to enable process optimization.

Measurement of Silicon Nitride

Using industry-proven spectrometer technology and proprietary measurement algorithms, Helios SCAN-tn combines speed, precise measurement and easy operation – all of which are needed to optimize processes at lowest cost and shortest line downtime.

Functions of Helios LAB-tn

Helios LAB-tn is a measurement system with an easy to use one-axis sample table that enables you to create coating profile scans for the layer thickness as well as for the refractive index of the coated wafer with a few seconds!

  • Single-point measurement √
  • Layer thickness √
  • Refractive index √
  • Manual one axis positioning table √
  • Wafer-coating profile scans √
  • Table integrated reference √
  • Cost effective coating measurement tool √

Highlights of Helios LAB-tn

Layer Thickness and Refractive Index of Silicon Nitride
  • Offline / contactless and non-destructive
  • High-speed manual profile scan function


Works for all relevant Types
  • mc- & pc-wafers (polished, rough or textured)
  • 125x125mm / 156x156mm
Works for all relevant Types of Textures
  • Isotropic and anisotropic chemically etched
  • RIE (Reactive Ion Etched)
Works for all relevant Types of Textures
  • PE-CVD
  • Magnetron Sputtering
Easy Operation
  • Pre-configured mapping templates
  • No special skills required for operation
  • Position the wafer. Start measurement. GO!


Helios LAB-tn



Inline measurement of SiN coating thickness and refractive index on solar wafers direct after the coating process



Inline gap distance control of Silicon melt and heat shields in crystal pullers