Thermal desorption spectra of SiO2 films deposited on Si and on thermal SiO2 by tetraethylorthosilicate/O-3 atmospheric-pressure chemical vapor deposition

SiO2 films deposited on Si and on thermal SiO2 by tetraethylorthosilicate [ TEOS, Si(OC2H5)(4)]/O-3 atmospheric-pressure chemical vapor deposition (APC VD) were analyzed by thermal desorption spectra (TDS). The TDS results show that more silanols were incorporated during deposition and more water was absorbed during and after deposition in films deposited on Si substrates th an on thermal oxide substrates. The latter result indicates that the elimin ation of water by-products is not the limiting step in TEOS/O-3 APCVD. Base d on the former result, a silanol model was proposed for the surface proces ses. On surfaces with a uniform and high density of silanol sites, or on wh ich silanols readily form under TEOS/O-3 APCVD conditions, the active silan ol groups in the gas phase contribute to film formation and replenish silan ol sites, resulting in continuous, high growth rates. On surfaces with few silanol sites, it is difficult to form silanol sites and the nonsilanol-con taining polysiloxanes contribute to film formation, resulting in continuous , low growth rate. This model explains well both the surface dependence and the memory effect of TEOS/O-3 APCVD. (C) 1999 American Institute of Physic s. [S0021-8979(99)07110-8].