Dissociation processes in plasma enhanced chemical vapor deposition of SiO2 films using tetraethoxysilane

Abstract

Dissociations in plasma enhanced chemical vapor deposition for SiO2 deposition using tetraethoxysilane (TEOS) were investigated by means of mass spectrometry. First, we showed basic dissociation patterns of TEOS as a function of electron energy. It was shown that TEOS dissociates by electron impact at electron energies below 8 eV, removing the ethyl group (C2H5). Next, we presented dissociation patterns in TEOS/He plasma. Finally, dissociation in TEOS/O2 plasma was studied. It was shown that high molecular intermediate products containing carbon and hydrogen, such as Si(OC2H5)2H, Si(OC2H5)2OCH3, and Si(OC2H5)3OCH2, are present only in the TEOS/He plasma but not in the TEOS/O2 plasma. It was also shown that eliminated hydrocarbon gases such as C2H2, C2H4, C2H5, and OC2H5 are converted into H2O and CO2. Fourier-transformed infrared and x-ray photoelectron spectroscopy studies revealed that the degree of impurity concentration in the film decreased with increasing O2 concentration. Characteristics of metal–insulator–semiconductor devices reflected the degree of impurity concentration in the oxide films. It was found that oxygen gas plays an indispensable role for preparing high quality SiO2 films by oxidizing the intermediate dissociation products and eliminating hydrocarbon gases.