AVS 52nd International Symposium
    Surface Science Friday Sessions
       Session SS1-FrM

Paper SS1-FrM3
Optical Second Harmonic Generation as a Diagnostic Tool in Ar@super +@ and XeF@sub 2@ Beam Etching Studies of Silicon

Friday, November 4, 2005, 9:00 am, Room 202

Session: Surface Modification through Etching
Presenter: J.J.H. Gielis, Eindhoven University of Technology, The Netherlands
Authors: J.J.H. Gielis, Eindhoven University of Technology, The Netherlands
A.A.E. Stevens, Eindhoven University of Technology, The Netherlands
P.M. Gevers, Eindhoven University of Technology, The Netherlands
H.C.W. Beijerinck, 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
Correspondent: Click to Email
Insight into surface and interface properties during plasma etching of micro- and nanostructures is essential to obtain optimal device performance. In this work we study surface and interface processes during etching of Si by implementing the surface and interface sensitive nonlinear optical technique of second harmonic generation (SHG) in a UHV multiple-beam experiment including an Ar@super +@ ion gun and a XeF@sub 2@ beam. SHG has been applied both spectroscopically and in real-time to study H-terminated Si(100) during ion bombardment and (subsequent) XeF@sub 2@ etching using a fs Ti:sapphire laser. Low-energy (50-1000 eV) ion bombardment of c-Si results in a layer of amorphous silicon (a-Si) with a thickness of several nanometers and is expected to create defects such as dangling bonds and strained bonds in this damaged layer. For the applied fundamental photon energy range of 1.35-1.75 eV the SHG signal for c-Si is mainly governed by a two-photon resonance at 3.3 eV related to strained Si-Si bonds in the surface region. This resonance has been characterized before, during, and after ion-induced etching of H-terminated Si(100). It has for example been observed that the resonance at 3.3 eV substantially increases in amplitude during ion bombardment while an additional broad resonance at 3.2 eV seems to emerge. From comparison with spectroscopic ellipsometry studies and by XeF@sub 2@ dosing experiments, the former resonance is likely to originate mainly from strained Si-Si bonds at the a-Si / c-Si interface while the latter seems to be related to strained bonds in the a-Si surface region. Prolonged XeF@sub 2@ etching of a-Si and c-Si results in an almost complete quenching of the SHG signal, followed by a partial recovery of the SHG signal in which two separate resonances can be distinguished. The dynamics of the spectral SHG signal can aid in understanding the role of strained bonds in the Ar@super +@ and XeF@sub 2@ etching process of silicon.