A Mass Spectrometric Study of Reaction Mechanisms in Chemical Vapor Deposition of (Ba, Sr)TiO3 Films

Reaction mechanisms in chemical vapor deposition (CVD) of SrTiO3 films have been studied using dipivaloylmethanato (DPM) complexes as sources, to gain insight into the complicated mechanisms for the CVD of (Ba, Sr)TiO3 films. Thermal decomposition processes were investigated for Sr(DPM)2 and TiO(DPM)2 using quadruple mass spectrometry (QMS), and the sticking probabilities of film precursors were estimated from trench coverages of SrO, TiO2 and SrTiO3 films. Intense signals at m/e=126 and 110 were observed in the decomposition spectra from Sr(DPM)2 and TiO(DPM)2, respectively, and their intensities increased substantially during the initial stages of reaction. This indicates that the m/e=126 and 110 peaks are attributable to products derived directly from Sr(DPM)2 and TiO(DPM)2, respectively. In the mixture of Sr(DPM)2 and TiO(DPM)2, the rate of increase of the intensity of the m/e=126 peak was reduced, while the peak at m/e=110 continued to increase with time. This implies that the decomposition rate for Sr(DPM)2 was reduced, and different products were produced in the mixture. The sticking probabilities for SrO, TiO2 and SrTiO3 film precursors were estimated to be 0.5, 0.03 and 0.05, respectively; the sticking probability for SrTiO3 was found to be much lower than the average of those for SrO and TiO2. Based on these results, we conclude that different film precursors are produced in the mixture of Sr(DPM)2 and TiO(DPM)2 during SrTiO3 film deposition.