XPS Evaluation of Samples Surface Cleaned by the XEI Evactron^®

Abstract

With the advent of field emission gun equipped SEMs and TEMs with clean vacuum systems, it has been shown repeatedly that the surface cleanliness of samples exposed to the small, high current density electron beam available in these instruments is critical with respect to controlling hydrocarbon contamination under the electron beam. in previous studies of dedicated plasma cleaners for TEM samples by one of the authors (SDW), it was shown that surface analytical techniques are the best methods for determining the effectiveness of such cleaners in removing hydrocarbons from the samples’ surfaces. in the current study, some of the experiments that were used in these previous studies were repeated using the XEI Evactron^® system in order to compare the relative effectiveness of this system for surface cleaning of EM samples.

Figure 1 shows a picture of the sample introduction chamber of a VG Scientific ESCALAB Mkll system (XPS) with the Evactron^® in place. The Evactron^® system consists of an RF head unit that attaches to the vacuum chamber with an adaptable flange, an RF impedance matching unit, and an RF generator/vacuum controller. Although a 100% O₂ system can be used and is recommended, for safety reasons, a 20%O₂/80%Ar by volume gas mixture was selected because of the hydrocarbon oil used in the mechanical pump. Cleaning was also performed using laboratory air. The major difference between the dedicated plasma cleaners and the Evactron^® configuration is that the sample is not immersed in the plasma but is exposed to the activated oxygen species in the downstream flow.