Plasma analyser for plasma-assisted surface process diagnostics up to 100 mbar

Abstract

Ion beam mass spectrometer (IBMS) has been developed for in situ, real-time monitoring of the ion composition of a plasma in the vicinity of the substrate surface up to a pressure of 100 mbar. IBMS is a quadruple mass spectrometer-based plasma sampling system installed into a separately pumped small analysis chamber. The top part of the IBMS is specially designed to serve as the sample holder of the reactor chamber. A technique containing wet etching and laser treatment has been developed to form an orifice in various substrates, that matches the pressure range to be studied. This orifice samples the particles arriving onto the surface from the plasma, but is small enough to maintain effusive gas flow into the analysis chamber. Behind the orifice, a specially designed ion optics directs the ions coming from the process chamber into the QMS for mass and energy separation. Since particles are not altered after sampling, non-stable species can also be detected. The ion optics ensures that a high rate of ions reaches the QMS. The intensity ratios in the spectra correspond to the concentration ratios of the ions arriving to the substrate surface. The QMS is also equipped with a conventional cross beam ion source allowing measurements of neutral species with post-ionization. The performace of the system is demonstrated in a microwave plasma enhanced diamond CVD system.