AVS 52nd International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS2-MoA

Paper PS2-MoA7
Spectroscopic and Real-Time Study of Ar@sup +@ and XeF@sub 2@ Etching of Si(100) by Second Harmonic Generation

Monday, October 31, 2005, 4:00 pm, Room 304

Session: Silicon Etching
Presenter: A.A.E. Stevens, Eindhoven University of Technology, The Netherlands
Authors: A.A.E. Stevens, Eindhoven University of Technology, The Netherlands
P.M. Gevers, Eindhoven University of Technology, The Netherlands
J.J.H. Gielis, Eindhoven University of Technology, The Netherlands
M.C.M. Van De Sanden, Eindhoven University of Technology, The Netherlands
W.M.M. Kessels, Eindhoven University of Technology, The Netherlands
H.C.W. Beijerinck, Eindhoven University of Technology, The Netherlands
Correspondent: Click to Email
To gain new insights into the fundamental processes occurring at surfaces during plasma etching, Second Harmonic Generation (SHG) has been employed to study the etching of Si(100) in an Ar@sup +@/XeF@sub 2@ beam etching experiment. SHG by a medium is only allowed when inversion symmetry of the medium is broken and is therefore possibly extremely sensitive to surfaces and interfaces. Using a Ti:Sapphire laser in the 710 to 920 nm wavelength range the strain-induced resonance of Si-Si bonds (2.70-3.44 eV) has been probed before, during and after etching by Ar@sup +@ ions and XeF@sub 2@. Low-energy (20-2000 eV) ions impinging onto the Si(100) create a damaged, amorphized Si layer, which leads to an enormous increase in the SH signal within less than 1 ML Ar@sup +@ dose, and broadening of the resonance, indicative for an amorphous medium. XeF@sub 2@ passivation of the surface after the ions are switched off reveals that the signal originates not only from the surface but also from a buried interface between the damaged and crystalline silicon. At the switch-on of the XeF@sub 2@ after the ion bombardment an immediate increase of the SH signal (at 3.42 eV) can be observed showing an instant reaction of F with the highly reactive amorphous silicon surface. For XeF@sub 2@ etching of Si(100) two separate spectral features in the SH signal can be distinguished. After the XeF@sub 2@ is switched off, the spectral features change, indicating a reconstruction of the reaction layer. Furthermore, dosing a hydrogen terminated surface with XeF@sub 2@ shows an increase in the SH signal over the full spectral range before the actual etching begins as a result of the initial binding of F to Si. These and other observations will be discussed, which have led to some surprising new insights in the etch mechanism of Ar@sup +@ and XeF@sub 2@ of Si(100), showing that SHG is a promising, powerful diagnostic tool for surface sensitive studies of etch mechanisms.