Montioring Coating Processes in Vacuum Chambers

Important parameters that need to be monitored during coating processes, such as layer thickness, composition, surface finish, light transmission, reflectance, polarization ability, and others, can be done by spectroscopy and spectroscopic interferometry.

Fibre optics provide a versatile tool to take light in and out of the remote vacuum and clean room chambers and at the same time organise the select measurement geometry for the coating analysis.

The illumination of and detection from the coating layering can be organised at different fibre positions relative to the coating to allow specular reflection, diffuse reflection, transmission, polarisation, interference, fluorescence and even Raman scattering to be measured.

The fibre optics can be arranged to monitor several parameters simultaneously or to measure at different spatial positions or masking conditions simultaneously.

For on-line production, several fibre optic sensors with suitable geometries can be placed across the web to monitor the production run. In some cases the ionic source, for example a plasma source, can be monitored for spectral emission to confirm its conditional efficiency during the operating process.

Most applications require a dedicated composition for the monitoring system. You can contact us for confidential advice on what items are best for your application. Here is just one system example.

In this case a reflection sensor is monitoring an on-line coating process on a web. Light is passed into the vacuum area via a vacuum feed through  and then passes to the reflectance sensor. The reflected light returns via another feedthrough to a measurement spectrometer channel.

The reflectance sensor itself can be disconnected locally using the SMA interconnects. A second channel can be added for reference measurement and to compensate for fluctuations in the light source.

A typical setup for vacuum measurements is shown in the illustration above.

Typical components used in vacuum measurements