AVS 45th International Symposium
    Plasma Science and Technology Division Friday Sessions
       Session PS-FrM

Paper PS-FrM7
Experimental Investigation of the Respective Roles of Oxygen Atoms and Electrons in the PECVD Deposition of SiO@sub 2@ in O@sub 2@/TEOS Helicon Plasmas

Friday, November 6, 1998, 10:20 am, Room 318/319/320

Session: Plasma-Surface Interactions - II
Presenter: A. Granier, Institut des Materiaux de Nantes, France
Authors: A. Granier, Institut des Materiaux de Nantes, France
C. Vallée, Institut des Materiaux de Nantes, France
A. Goullet, Institut des Materiaux de Nantes, France
K. Aumaille, Institut des Materiaux de Nantes, France
G. Turban, Institut des Materiaux de Nantes, France
Correspondent: Click to Email
The respective roles of electrons and oxygen atoms in the plasma enhanced chemical vapor deposition of SiO@sub 2@-like films are investigated in a rf helicon oxygen/tetraethoxysilane (TEOS) plasma. The O atom density (a few 10@super 13@ cm@super -3@) and flux are monitored by actinometry and the electron density (a few 10@super 10@ cm@super -3@) by combination of optical emission spectroscopy (OES) and Langmuir probe analyses. The variations of the electron and atomic oxygen densities are studied as a function of the rf power (up to 500 W), the pressure (1-25 mTorr) and the organosilicon fraction in the O@sub 2@/TEOS plasma, simultaneously to the measurement of the deposition rate (using in situ ellipsometry) and analysis of the deposited films. The incorporation of ethoxy and silanol groups is determined from infrared spectroscopy. The refractive index and density of the films are deduced from UV-visible spectroscopic ellipsometry and gravimetric measurements respectively. It is shown that the TEOS fragmentation and the deposition rate are strongly related to the electron density while the main role of oxygen atoms is the etching of the organic part of the growing film, and not to dissociate the organosilicon molecules. In order to gain insight into the etching of the growing film by oxygen atoms, organosilicon films freshly deposited in a TEOS rich plasma are exposed to a pure oxygen plasma. During this post-exposure to an oxygen plasma, the film and the plasma are analyzed by ellipsometry and OES respectively : the film etching is clearly evidenced by the significant decrease in film thickness and the emission from CO, OH and H excited species which are related to the CO, CO@sub 2@ and H@sub 2@O etching products. It is furthermore shown that the film undergoes structural modifications over several ten nanometers.