INVESTIGATION OF LOW-TEMPERATURE SIO2 PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITION

Low temperature (<270 degrees C) plasma enhanced chemical vapor deposi tion (PECVD) of SiO2 thin films using tetraethylorthosilicate (TEOS) a nd O-2 plasma was investigated. Depositions were carried out in a PECV D reactor with a helical resonator discharge source. Transmission infr ared spectroscopy, spectroscopic ellipsometry, and wet etch rate measu rements were used to characterize the deposited films as a function of rf power, gas composition, and substrate temperature. Most pronounced effects were observed when the substrate temperature and TEOS:O-2 flo w ratio R were varied. Good quality SiO2 films can be obtained at high temperature and/or low R. For R>0.1, while the deposition rate was we akly dependent on temperature between 260 and 100 degrees C, it increa sed almost by a factor of 2 between 100 and 45 degrees C. This is also accompanied by drastic changes in film properties such as refractive index, increase in OH and -OC2H5 content, and decrease in film density . Studies using in situ attenuated total reflection Fourier transform infrared (ATR FTIR) spectroscopy indicated that stable good quality Si O2 films without any SiOH at higher temperature (250 degrees C) and wi th very little SiOH at room temperature could be deposited using very low R. Based on the understanding provided by ATR FTIR, films with pro perties approaching to these of thermal oxide have been deposited at r oom temperature. (C) 1996 American Vacuum Society.