IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Plasma Science Friday Sessions
       Session PS-FrM

Paper PS-FrM4
Time-resolved Radical Measurements in a Remote Silane Plasma Using the Cavity Ringdown Absorption Technique

Friday, November 2, 2001, 9:20 am, Room 104

Session: Diagnostics III
Presenter: J.P.M. Hoefnagels, Eindhoven University of Technology, The Netherlands
Authors: J.P.M. Hoefnagels, Eindhoven University of Technology, The Netherlands
A.E.E. Stevens, Eindhoven University of Technology, The Netherlands
W.M.M. Kessels, Eindhoven University of Technology, The Netherlands
D.C. Schram, Eindhoven University of Technology, The Netherlands
M.C.M. van de Sanden, Eindhoven University of Technology, The Netherlands
Correspondent: Click to Email
The highly sensitive cavity ringdown spectroscopy technique (CRDS) has been used for the determination of the density and plasma chemistry of SiH@sub x@ radicals in our remote silane plasma, which is used for high rate deposition of a-Si:H and µc-Si:H. Recently, a new CRDS based technique has been developed for measuring time-resolved radical densities (@tau@-CRDS) to obtain further insight into the dynamics of SiH@sub x@ radicals and to study the interaction of these radicals with the depositing surface. In @tau@-CRDS, the plasma is modulated and the corresponding response of the SiH@sub x@ radical density is monitored by sampling the SiH@sub x@ density at various times. For this measurement, a "state of the art" data acquisition system (100 MHz, 12 bit) has been developed such that single CRDS transients can be handled up to a repetition rate of 2 kHz. It will be shown that single transient handling improves the signal-to-noise ratio drastically, even for conventional CRDS measurements. The modulation of the plasma is done by application of pulsed rf power to the substrate holder in addition to the regularly operating remote plasma. This creates only a minor additional SiH@sub x@ radical density. In this way, gas phase and surface reactivities of the species are obtained under steady state plasma operation conditions. The feasibility of the @tau@-CRDS technique has been proven on SiH radicals probing the A@super 2@@DELTA@<-X@super 2@@PI@ electronic transition at ~413 nm. By using different modulation frequencies the measurements have also revealed that a previously unidentified broadband absorption on this wavelength is due to a rather unreactive species created in the silane plasma. Furthermore, @tau@-CRDS measurements on Si and SiH@sub 3@ will be presented and the gas phase and surface reactivity of these species will be discussed on the basis of a model.