Performance of an 8" RIE etching system - the effect of cathode cover mateials

Abstract

Within the project "High Resolution Plasma Etching in Semiconductor Technology - Fundamentals, Processing, Equipment", a new and versatile 8" 3-chamber single wafer RIE etching system has been constructed. Process development and comprehensive investigations of operating and etching behaviour have been undertaken for this machine. In this paper, the influence of different cathode cover materials on the etching performance will be presented. In the case of silicon etching with pure SF6 emission spectroscopy and quadrupole mass spectrometry have been applied to reveal densities of neutral particles and ions in the etch plasma under various operating conditions and for commonly used cathode cover materials (i.e. coated alumina, stainless steel, quartz, ARDEL, MACOR). On the other hand etched structures have been investigated by SEM to comment on anisotropy of the etch process, and etchrate measurements have been performed. The results elucidate the important role of non-inert cathode cove ring materials, as supplier of etch species and as a consumer of them as well. Consequently a strong loading effect is found, depending on both the size of the etched areas and cover material. An attempt to make a correlation between plasma species and etch behaviour is made for some surveyable cases. (IMT