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

Abstract

Reaction mechanisms in chemical vapor deposition (CVD) of SrTiO 3 films have been studied using dipivaloylmethanato (DPM) complexes as sources, to gain insight into the complicated mechanisms for the CVD of (Ba, Sr)TiO 3 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, TiO 2 and SrTiO 3 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, TiO 2 and SrTiO 3 film precursors were estimated to be 0.5, 0.03 and 0.05, respectively; the sticking probability for SrTiO 3 was found to be much lower than the average of those for SrO and TiO 2 . Based on these results, we conclude that different film precursors are produced in the mixture of Sr(DPM) 2 and TiO(DPM) 2 during SrTiO 3 film deposition.