Thin Film Deposition from Plasmas of Tetramethylsilane– Helium–Argon Mixtures with Oxygen and with Nitrogen NILSON C. DA CRUZ, STEVEN F. DURRANT, MA ´ RIO A. BICA DE MORAES Laborato ´ rio de Processos de Plasma, Instituto de Fı B sica Gleb Wataghin, Universidade Estadual de Campinas, CP 6165, 13083-970, Campinas, SP, Brazil Received 11 July 1997; accepted 7 January 1998 ABSTRACT: Films were produced by plasma enhanced chemical vapor deposition ( PECVD ) of tetramethylsilane ( TMS ) – helium – argon mixtures with either oxygen or nitrogen in a vacuum system fed with radiofrequency power. Actinometric optical emis- sion spectroscopy was used to determine trends in the concentrations of plasma species of interest (H, CH, O, CO, and CN) as a function of the ratio of the inorganic reactive gas (oxygen or nitrogen) to the monomer (TMS) in the system feed. As the ratio of oxygen to TMS in the feed is increased, the degree of oxygenation of the deposited material, as revealed by transmission infrared spectroscopy, is also increased. Simi- larly, the degree of nitrogenation of the films increases with increasing nitrogen to monomer ratio in the feed. Strong correlations exist between the plasma concentrations of the above-mentioned plasma species and film structure and composition.  1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1873–1879, 1998 Keywords: plasma-enhanced chemical vapor deposition; actinometric optical emission spectroscopy; tetramethylsilane; nitrogen; oxygen INTRODUCTION on optical devices, 22,23 semiconducting devices, 24 moisture sensors, 25 and coatings for lithographic processes in integrated circuit fabrication 13 are Plasma deposition allows the production of or- important applications of these materials. ganic polymer films from monomers that cannot Understanding of the mechanisms occurring in be polymerized by conventional means. 1 Such the discharge is generally held to be much less films are typically pinhole free and exhibit good advanced than the practical applications of the adhesion to metal, glass, and other insulating films themselves. In this work, both discharges substrates. Amorphous organosilicon polymer films have been deposited from monomers such and films were studied to shed some light on the as hexamethyldisiloxane, 2 hexamethyldisilazane, 3 mechanisms at work in the plasma. Tetrameth- and vinyltrimethylsilane. 4 Film deposition from ylsilane (TMS) was used as the monomer, and tetramethylsilane ( TMS ) alone has received con- either oxygen or nitrogen was used as a como- siderable attention over the last 20 years. 5–16 In nomer. In both mixtures helium was used as a addition, a few studies have shown that the use dilution gas and argon as a probe gas for optical of comonomers such as hydrogen, 17 ammonia, 18 emission measurements, as explained below. tetrafluoromethane, 19 and oxygen 20,21 allows vari- Actinometric optical emission spectroscopy ation of the physical and physicochemical proper- [AOES], suggested by Coburn and Chen, 26 has ties of the deposited films. Protective coatings been extensively applied to studies of polymeriz- ing discharges. 27–31 This method, which involves adding a small amount of a noble gas or actinome- Correspondence to: S. F. Durrant. ter to the plasma feed, and monitoring of a charac- Journal of Polymer Science: Part B: Polymer Physics, Vol. 36, 1873–1879 (1998)  1998 John Wiley & Sons, Inc. CCC 0887-6266/98 / 111873-07 teristic emission from species of interest, X , and 1873 8q5d 9707009 / 8q5d$$7009 05-18-98 16:56:40 polpa W: Poly Physics