| AVS 54th International Symposium | |
| Plasma Science and Technology | Wednesday Sessions |
| Session PS2-WeM |
| Session: | Plasma-Surface Interactions I |
| Presenter: | J.J.H. Gielis, Eindhoven University of Technology, The Netherlands |
| Authors: | J.J.H. Gielis, Eindhoven University of Technology, The Netherlands P.M. Gevers, Eindhoven University of Technology, The Netherlands P.J. van den Oever, Eindhoven University of Technology, The Netherlands A.A.E. Stevens, 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 |
Surface and interface properties increasingly govern device performance in microelectronics, therefore, obtaining profound knowledge of these properties in real time during plasma processing is essential. In this respect, the nonlinear optical technique of second-harmonic generation (SHG) is very promising, as it has proven to be an ultra-sensitive probe for surface and interface states such as dangling bonds and strained Si-Si bonds in crystalline Si (c-Si) surface science.1 In this work the real time and spectroscopic SHG response of amorphous silicon (a-Si) will be addressed in two areas of plasma processing, ion-assisted etching of c-Si and deposition of hydrogenated amorphous silicon (a-Si:H). In addition, spectroscopic ellipsometry was used to deduce linear optical properties. The experiments were carried out under well-defined conditions in high vacuum setups, using ion and radical beams to circumvent the complexity of the plasma.2 Ion bombardment of c-Si using a low-energy Ar+-ion gun (70-1000 eV) results in a layer of a-Si with a thickness of several nanometers. For fundamental photon energies from 1.35-1.75 eV, the SHG signal increases with an order of magnitude upon ion bombardment and it is shown that the SHG signal is governed by a two-photon resonance at 3.36 eV, related to modified Si-Si bonds at the a-Si/c-Si interface with an additional a-Si surface contribution. In the 0.8-1.1 eV fundamental photon energy range the increase in SHG signal is even stronger. It is discussed that the time-resolved SHG signal is governed by dangling bond creation and annihilation dynamics at the a-Si surface and a-Si/c-Si interface. Thin films of a-Si:H deposited on c-Si by a SiH3 dominated beam have been investigated with SHG in the same photon energy ranges. For many applications, such as heterojunction solar cells, the abruptness of the a-Si:H/c-Si interface is crucial. Also in this system the SHG signal displays a strong resonance at ~3.3 eV from the a-Si:H/c-Si interface. It will be demonstrated that real time SHG provides a method to distinguish between direct heterointerface formation and nanometer-level epitaxial growth at a very early stage of film growth.
1 U. Höfer, Appl. Phys. A 63, 533 (1996).
2 J. W. Coburn and H. F. Winters, J. Appl. Phys. 50, 3189 (1979).