HELios Scan-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 SCAN-tn

Helios SCAN-tn is a fully automatic measurement system that enables you to create coating distribution maps for the layer thickness as well as the refractive index of the coated wafer within less than one minute!

  • Layer thickness √
  • Refractive index √
  • Automatic XY positioning table √
  • Pre-configured mapping templates √
  • Automatic calibration √
  • Automatic coating distribution plots √
  • Single-point measurement √

Highlights of Helios SCAN-tn

Layer Thickness and Refractive Index of Silicon Nitride
  • Offline / contactless and non-destructive
  • High-speed mapping 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
  • Select recipe. Start measurement. GO!



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