Temperature effect on structural properties of boron oxide thin films deposited by MOCVD method

Boron oxide (B₂O₃) thin films were deposited on Si (100) substrates using a single source precursor by thermal MOCVD method under a pressure of 150 mTorr and the temperature range of 500-650 °C. Tri-isopropyl borate ([(CH₃)₂CHO]₃B) was used as a precursor without carrier and bubbler gases. In this study, the structural properties of boron oxide thin films with various deposition temperatures were mainly investigated. A highly oriented cubic B₂O₃ thin film in the [310] direction was grown on Si (100) substrate at 600-650 °C. XPS analysis shows that the chemical compositions of as-grown film at 500-600 °C have a non-stoichiometric value as B₂O_3+x, while those of films grown at above 600 °C have a stoichiometric value as B ₂O₃ film. From FT-IR and contact angle analysis, we realized that crystallinity of the deposited films was decreased by B-O-H bond formation. We also observed the surface morphology, grain size, and film thickness of the as-grown films by SEM. The average grain sizes and film thickness are varied, in the range of 10-40 and 200-500 nm, depending on deposition temperature. With increasing deposition temperature, the grain size as well as film thickness are also increased. In conclusion, the structural properties of the as-grown boron oxide thin films are strongly dependent upon deposition temperature. Therefore, as mentioned, more stoichiometric films are produced in the surrounding of high temperature (above 600 °C). In addition, we formed that the film crystallinity is also improved with increasing deposition temperature.