Spectroscopic Study on Metallorganic Chemical Vapor Deposition of Manganese Oxide Films

Abstract

The reaction mechanism of a manganese precursor, tris͑dipivaloylmethanato͒manganese ͓Mn͑DPM͒ 3 ͔, was investigated in liquid delivery metallorganic chemical vapor deposition ͑MOCVD͒ of manganese oxide films. The behavior of Mn͑DPM͒ 3 in the gas phase was analyzed under actual CVD conditions by in situ infrared absorption spectroscopy. The temperature dependence of the infrared absorption indicates that Mn͑DPM͒ 3 was decomposed in the gas phase under the actual deposition conditions. We discuss the correlation between the thermal decomposition of Mn͑DPM͒ 3 in the gas phase and film deposition of manganese oxides. When the substrate temperature is raised above 360°C, the deposition rate decreases, synchronized with the decrease of the infrared absorption by Mn͑DPM͒ 3 in the gas phase. The oxidation state of Mn in the deposited films was also investigated by highresolution X-ray fluorescence spectroscopy. No significant difference in the oxidation state of Mn is found between the deposited films and the starting source material, Mn͑DPM͒ 3 .Manganese-containing oxides have been receiving much attention due to their interesting physical and chemical properties and their related applications to rechargeable batteries, catalysts, sensors, and magnetic devices. Thin films of manganese-containing oxides have been synthesized by various deposition methods. From the viewpoint of practical use in device processes, metallorganic chemical vapor deposition ͑MOCVD͒ is regarded as one of the most promising techniques for the deposition of manganese-containing oxide films because of its excellent step coverage and good composition controllability. The MOCVD technique using liquid source delivery has the advantage of providing a stable and efficient supply of source materials. Although intensive work has been performed for process development, 1-3 the deposition chemistry is still not well understood in the liquid source MOCVD of manganese oxide films. In view of a lack of established guiding principles to control film quality, attempts to accumulate experimental data on gas-phase and surface reactions under actual CVD conditions are necessary to understand the film deposition mechanism. Recently, we have demonstrated that spectroscopic techniques such as in situ infrared absorption spectroscopy 4-10 and microdischarge optical emission spectroscopy 11,12 are useful for studying gas-phase reactions of various MOCVD precursors.In this work, in situ infrared absorption spectroscopy was employed under actual liquid delivery CVD conditions to understand gas-phase reactions of a manganese precursor, tris͑dipivaloylmetha-nato͒manganese ͓Mn͑DPM͒ 3 ,Mn͑C 11 H 19 O 2 ͒ 3 ͔. The chemical structure of Mn͑DPM͒ 3 is shown in Fig. 1. We observed the temperature dependence of the infrared absorbance and measured the deposition rate and atomic composition of the deposited films. The spectroscopic data on the gas-phase reactions, such as thermal decomposition and oxidation, were correlated with the characteristics of the deposited oxide films. Figur...

Intermolecular interaction between rare earth and manganese precursors in metalorganic chemical vapor deposition of perovskite manganite films

“…The vibration peak at 869 cm -1 is assigned to C-C(CH 3 ) 3 stretching mode with the in-plane DPM ring deformation [27]. For comparison, similar experimental data on the individual source molecules of Pr(DPM) 3 and Mn(DPM) 3 [16,26] are also included in Fig. 3.…”

“…Figure 3 Temperature dependence of the infrared absorption of the mixture of Pr(DPM) 3 and Mn(DPM) 3 at 869 cm -1 . Similar experimental data on the individual source molecules of Pr(DPM) 3 and Mn(DPM) 3 are added for comparison [16,26]. Figure 4 shows the temperature dependence of the infrared absorption spectra of the mixture of La(DPM) 3 and Mn(DPM) 3 at the substrate temperature between 240 and 640 o C. The mixing ratio of La(DPM) 3 and Mn(DPM) 3 was set to be 1.0.…”

“…Figure 5 shows the temperature dependence of the infrared absorption of the mixture of La(DPM) 3 and Mn(DPM) 3 at 869 cm -1 . For comparison, the similar experimental data on the individual source molecules of La(DPM) 3 and Mn(DPM) 3 [25,26] are also included in Fig. 5.…”

“…In view of a lack of established guiding principles to control film quality, attempts to accumulate experimental data on gas-phase and surface reactions under actual CVD conditions are necessary to understand the film deposition mechanism. In recent years, we have demonstrated that in situ infrared absorption spectroscopy [9,16,25,26] is useful for studying gas-phase reactions of various MOCVD source molecules.…”

“…We observed infrared absorption spectra under actual CVD conditions. Details of the in situ infrared absorption measurements have been described elsewhere [9,16,25,26]. Manganite films were deposited on Si(100) substrates.…”