Angularly and Spatially Resolved Measurements of the Energy Flux in an RF Plasma Using a Thermal Probe

The total energy flux for an RF plasma (13.56 MHz) has been measured by means of a simple thermal probe. The procedure is based on the measurement of time dependent changes of the probe temperature during the plasma process. A substrate dummy which is thermally isolated and inserted into the plasma at substrate position served as thermal probe which can be moved in vertical and horizontal directions in order to measure the different energy fluxes and their distribution in the reactor vessel. The knowledge of the spatial distribution is important, for example, for coating or sputtering processes. Different contributions to the total energy flux are identified by different orientations of the thermal probe, e.g., if the probe is facing the RF electrode the energy flux is much higher than in the opposite direction. This difference can be addressed to an additional energetic contribution due to secondary electron emission from the powered RF electrode.