IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Surface Science Tuesday Sessions
       Session SS3-TuP

Paper SS3-TuP10
Real-Time Monitoring of Desorption and Restoration on Cl/Si(111) Surface with Second Harmonic Generation

Tuesday, October 30, 2001, 5:30 pm, Room 134/135

Session: Adsorption/Desorption Poster Session
Presenter: K. Shudo, Yokohama National University, Japan
Authors: K. Shudo, Yokohama National University, Japan
T. Sasaki, Yokohama National University, Japan
M. Tanaka, Yokohama National University, Japan
Correspondent: Click to Email
Surface etching with halogen is most elementary process in semiconductor fabrication. To elucidate thermal process on Cl-covered Si(111)-1x1 surface, second harmonic (SH) generation was measured in real time with 1.17 eV photons from a pulsed laser (8 nsec). From isothermal change in the SH signal, energetics on related reactions can be discussed. On clean Si(111)-7x7 dimer-adatom-stackingfault (DAS) surfaces, SH intensity was calibrated in Cl-adsorption compared with temperature programmed desorption. The weakened SH signal by disappearing dangling bonds was interpreted as chlorine coverage on the surface. Initial sticking probability of Cl on the surface was determined to be 0.58, that is actually the same as obtained with SDR.@footnote 1@ Under the isothermal treatment of the Cl/Si(111)-1x1 surface from 843 to 963 K, time-evolution of SH recovery showed that fast and slow steps are involved in the process. The fast one turned out to be of a first order process. Temperature dependence of the rate in the fast component indicates a barrier of 2.1 eV. It corresponds to an energy against emerging of dangling bonds at desorption of silicon chlorides. The following slow component has 2.4 eV of barrier, being activation energy to reform the surface into 7x7 DAS structure. To reduce the dangling bond, 5x5 or 9x9 structures are known to appear temporarily before 7x7 DAS appears. The barrier is considered as the energy required for the slow structural restoration to form and/or move stacking faults. @FootnoteText@ @footnote 1@ Desorption from Cl/Si(111) is also discussed with surface differential reflectance (SDR) spectroscopy, presented elsewhere of SS17 in the conference.