Deposition of silicon oxide films from TEOS by low frequency plasma chemical vapor deposition

Abstract

Recently, TEOS has been studied as a silicon source of silicon oxide films deposited by plasma chemical vapor deposition (CVD) because the deposited films show good step coverage compared with films deposited from SiH4. In this work, the authors deposited silicon oxide films using TEOS as a silicon source by using a low frequency (50 Hz) plasma CVD. It has been demonstrated in previous articles that low frequency (50 Hz) plasma CVD can deposit high quality silicon nitride films and amorphous carbon films without substrate heating. It is found in the present work that the substrate heating at deposition is required to obtain acceptable electrical properties when silicon oxide films are deposited from a TEOS and oxygen mixture, even by low frequency (50 Hz) plasma CVD. The films deposited at 200 °C from the plasma of a 3% TEOS mixture were found to be high quality insulating films; the resistivity was 1016 Ω cm and the breakdown strength 7×106 V/cm. Moreover, Auger electron spectrum analysis revealed that carbon atoms were not detected from the films in spite of the presence of carbon atoms in the TEOS molecule. With optical emission spectrum analysis of the TEOS and oxygen mixture plasma, strong emissions from the CO and CO2 molecules were observed. It may be concluded that in the plasma carbon atoms react with oxygen atoms to yield the CO and CO2 molecules which are stable enough to remain in the gas and thus not be taken into the films.