THERMODYNAMIC STUDY, COMPOSITIONAL AND ELECTRICAL CHARACTERIZATION OFLPCVD SIO2-FILMS GROWN FROM TEOS N2O MIXTURES/

The theoretical phase diagram describing the growth of SiO2 films from TEOS and N2O mixtures within the temperature range 500-1100 degrees C and pressure 0.3 Torr has been obtained, minimizing the total Gibbs e nergy of the chemical system involved in the deposition. It was found that at temperatures up to 900 degrees C and N2O/TEOS molar ratios up to approximately 7, the SiO2 films deposited contained carbon impuriti es. For higher N2O/TEOS molar ratios the obtained films are carbon fre e. SiO2 films were grown from TEOS/N2O mixtures in a conventional hori zontal low pressure chemical vapor deposition reactor at temperatures of 710 degrees C and 820 degrees C and at a pressure of 0.3 Torr. Thes e films were analyzed using X-ray photoelectron spectroscopy, Rutherfo rd backscattering spectroscopy, atomic force microscopy and C-V measur ements taken on metal-insulator-semiconductor structures formed with t he deposited films as insulators. It was found that the films contain carbon impurities the concentration of which decreases with the increa se of N2O/TEOS molar ratio, in agreement with the results of the therm odynamic study. Carbon atoms were 90% bonded to other carbon atoms and only 10% to oxygen. It was found that the films are substoichiometric in oxygen with O/Si atomic ratios ranging between 1.95 and 1.80. The films were found to be positively charged, the charge increasing with N2O flow and decreasing with deposition temperature. (C) 1998 Elsevier Science Ltd.