Low-temperature plasmas are used in semiconductor and medical technology and surface engineering. Production process precision and production reproducibility are a growing challenge, especially in semiconductor technology, where components are becoming increasingly smaller.  A new technology from Ruhr University Bochum specifies process-relevant parameter with PROES (phase resolved optical emission spectroscopy).

The plasma’s light emissions are measured with a photomultiplier tube (PMT). The light is transmitted to the PMT through a light conductor.  Such a measurement results in a graph showing plasma emission intensity at given wavelengths with a time resolution of a few nanoseconds. This shows when and where there are electrons with certain energies in the plasma, providing information about process-relevant parameters such as flows of ions and radicals.

Advantages of this technology: It is minimally invasive; can be integrated into optical emission spectroscopy (OES) systems, which have little or no time resolution; costs little; and has low susceptibility to optic coatings. Analysis of time-resolved plasma emission provides deeper insights into the process than does standard OES, allowing plasma processes to be developed, optimized, and regulated in a targeted manner.