Inductively coupled plasma (ICP) is an excitation procedure that generates a plasma with high electron density and high plasma purity. The classic applications are in the low-pressure range (50 Pa) - with low-frequency excitation (13.56 MHz) and very high energy requirements (in the kW range). ICPs are mainly used in the semiconductor technology. Due to large-volume excitation of the plasma, the homogeneity and thus the size of the area to be processed are limited. An array of plasma jets can be used to compensate this disadvantage. The additional use of a ‘remote plasma’ means that this is generated and applied at separate locations. This allows to better control the chemistry and time development of the treatment. In addition, microwave excited plasmas (2.45 GHz) are relatively cold even at atmospheric pressure despite their high electron density (> 1019 m-3). All of these features are taken into account in the new source development at FBH. Due to their special design, these ICP sources do not only work with air and argon but also with highly reactive gases like fluor or chlorine.
The most important challenges with such plasma jet sources are:
- Efficient energy transfer to the plasma (> 60%, instead of classically 10%)
- Compact and robust adjustment of resonant frequency and impedance matching for operation with different gases
The FBH is investigating and developing microwave-powered ICP plasma sources in the frame of a DFG project in cooperation with the Ruhr University Bochum. In particular, it contributes its expertise in 3D simulation and the development of dedicated resonators and matching circuits as well as in the application of special measurement methods.