AVS 53rd International Symposium
    Thin Film Friday Sessions
       Session TF+EM-FrM

Paper TF+EM-FrM2
Optical and Morphological Studies on SiO@sub 2@-like Films Deposited by Means of Ion Bombardment- Assisted Expanding Thermal Plasma CVD

Friday, November 17, 2006, 8:20 am, Room 2022

Session: In-Situ/Ex-Situ & Real-Time Monitoring and Characterization
Presenter: A. Milella, Eindhoven University of Technology, The Netherlands
Authors: A. Milella, Eindhoven University of Technology, The Netherlands
M. Creatore, Eindhoven University of Technology, The Netherlands
M.A. Blauw, Eindhoven University of Technology, The Netherlands
M.C.M. Van De Sanden, Eindhoven University of Technology, The Netherlands
Correspondent: Click to Email
The role of ion bombardment in the growth of plasma-deposited thin films has been often investigated in literature as a route towards film matrix densification at low temperature, this latter being a requirement when thermally sensitive substrates, such as polymers, are studied. In the present paper we report our latest results on the densification of SiO@sub 2@-like films by applying an external rf bias to the substrate holder during film deposition by means of an Ar-fed expanding thermal plasma, in which hexamethyldisiloxane and oxygen are injected downstream. A comprehensive study of the optical properties of the deposited films, as determined by Spectroscopic Ellipsometry, with increasing dc bias voltage will be presented. In particular, it will be shown that ion bombardment can effectively improve film density when parameters such as the energy of the ions impinging the surface of the growing film and the ion-to-depositing radical flux ratio, are carefully controlled. Densification of film network by ion bombardment can be furthermore assessed by Fourier Transform IR spectroscopy, following changes in SiOSi asymmetric stretching absorption band with dc bias voltage. Film porosity increases with increasing deposition rate which results in a different absorption band shape. Surface morphology evolution of SiO@sub 2@-like films deposited under increasing dc bias voltage conditions as determined by Atomic Force Microscopy will be presented. In absence of ion bombardment, films display growth of spherical nodules distributed uniformly across the surface, with heights and lateral dimensions depending on the process parameters selected. Quantitative analysis shows that both RMS roughness and mean peak-to-valley distance decrease almost exponentially with increasing dc bias voltage. These results correlate with refractive index trends as determined from spectroscopic ellipsometry.