Amorphous Mixed TiO 2 and SiO 2 Films on Si(100) by Chemical Vapor Deposition

Amorphous thin films of composition Ti x Si 1-x O 2 have been grown by low pressure chemical vapor deposition on silicon (100) substrates using Si(O-Et) 4 and either Ti(O- i Pr) 4 or anhydrous Ti(NO 3 ) 4 as the sources of SiO 2 and TiO 2 , respectively. The substrate temperature was varied between 300 and 535°C, and the precursor flow rates ranged from 5 to 100 sccm. Under these conditions growth rates ranging from 0.6 to 90.0 nm/min were observed. As-deposited films were amorphous to X-rays and SEM micrographs showed smooth, featureless film surfaces. Cross-sectional TEM showed no compositional inhomogeneity. RBS revealed that x (from the formula Ti x Si 1-x O 2 ) was dependent upon the choice of TiO 2 precursor. For films grown using TTIP-TEOS x could be varied by systematic variation of the deposition conditions. For the case of TN-TEOS x remained close to 0.5 under all conditions studied. One explanation is the existence of a specific chemical reaction between TN and TEOS prior to film deposition. TEOS was mixed with a CCl 4 solution of TN at room temperature to produce an amorphous white powder (Ti/Si = 1.09) and 1 HNMR of the CCl 4 solution indicated resonances attributable to ethyl nitrate.