Strontium-based high dielectric materials such as SrTiO_3, and (Ba, Sr)TiO_3 have attracted great interest in recent years because of their high dielectric constants and small variations of electrical properties with frequency and aging treatment. Main applications are capacitor dielectrics for very...
Strontium-based high dielectric materials such as SrTiO_3, and (Ba, Sr)TiO_3 have attracted great interest in recent years because of their high dielectric constants and small variations of electrical properties with frequency and aging treatment. Main applications are capacitor dielectrics for very high density dynamic random access memory (DRAM) cells. Many research results for fabricating SrTiO_3 thin films by MOCVD (Metal Organic Chemical Vapor Deposition) and rf magnetron sputtering have been reported, but little work has been done on the plasma enhanced metal organic chemical vapor deposition (PEMOCVD) of SrTiO_3. One of the most critical parameters for the growth of high quality SrTiO_3 thin films is the substrate temperature. Hence, the design, construction, and performance of a substrate heater for PEMOCVD are described. This work is to model heat transfer of substrate heater and the results are compared with the experimental measurements. Also the effects of the pressure and rf source power on the substrate temperature was investigated. The substrate temperature increased linearly with the pressure and rf source power. From this work, the design of an efficient substrate heater was proposed. In this work, to study the growth characteristics and deposition mechanism of SrTiO_3 thin films by PEMOCVD, the films were deposited on Pt/Si and Ir/Si substrates using high purity titanuim isopropoxide(Ti(O- i ?C_3H_7)_4 TTIP), bis(2,2,6,6-tetramethyl-3,5-heptanedionato) strontium(Sr(tmhd)_2) and oxygen. Experiments were carried out under various operation conditions. Structural properties of as-deposited SrTiO_3 films were evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy dispersive spectrometry (EDS). Also decomposition mechanism was investigated for Sr(tmhd)_2 and TTIP using quadruple mass spectrometry (QMS). The decomposition of TTIP was substantially enhanced by increasing the rf source power, while that of Sr(tmhd)_2 increased with the substrate temperature. The deposition rates were quite dependent on bubbler temperature (T_b), substrate temperature (T_s), and rf source power. The optimum conditions for deposition of SrTiO_3 films on Pt/Si and Ir/Si substrates were; T_b = 220 ℃ for Sr(tmhd)_2 and 60 ℃ for TTIP, T_2 = 550 ℃, carrier gas flow rates of 130 sccm for Sr(tmhd)_2 and 40 sccm for TTIP, oxygen flow rate of 130 sccm, and rf power of 160W. There is no clear difference in growth characteristics on the two substrates. The surface morphology examined by AFM and SEM showed a smooth surface and good adhesion at the interface. Based on the growth characteristics of films, the deposition mechanism of SrTiO_3 films was proposed. It was found that the deposition of SrTiO_3 films was limited by the decomposition rate of Sr(tmhd)_2 on the substrate surface.
Strontium-based high dielectric materials such as SrTiO_3, and (Ba, Sr)TiO_3 have attracted great interest in recent years because of their high dielectric constants and small variations of electrical properties with frequency and aging treatment. Main applications are capacitor dielectrics for very high density dynamic random access memory (DRAM) cells. Many research results for fabricating SrTiO_3 thin films by MOCVD (Metal Organic Chemical Vapor Deposition) and rf magnetron sputtering have been reported, but little work has been done on the plasma enhanced metal organic chemical vapor deposition (PEMOCVD) of SrTiO_3. One of the most critical parameters for the growth of high quality SrTiO_3 thin films is the substrate temperature. Hence, the design, construction, and performance of a substrate heater for PEMOCVD are described. This work is to model heat transfer of substrate heater and the results are compared with the experimental measurements. Also the effects of the pressure and rf source power on the substrate temperature was investigated. The substrate temperature increased linearly with the pressure and rf source power. From this work, the design of an efficient substrate heater was proposed. In this work, to study the growth characteristics and deposition mechanism of SrTiO_3 thin films by PEMOCVD, the films were deposited on Pt/Si and Ir/Si substrates using high purity titanuim isopropoxide(Ti(O- i ?C_3H_7)_4 TTIP), bis(2,2,6,6-tetramethyl-3,5-heptanedionato) strontium(Sr(tmhd)_2) and oxygen. Experiments were carried out under various operation conditions. Structural properties of as-deposited SrTiO_3 films were evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy dispersive spectrometry (EDS). Also decomposition mechanism was investigated for Sr(tmhd)_2 and TTIP using quadruple mass spectrometry (QMS). The decomposition of TTIP was substantially enhanced by increasing the rf source power, while that of Sr(tmhd)_2 increased with the substrate temperature. The deposition rates were quite dependent on bubbler temperature (T_b), substrate temperature (T_s), and rf source power. The optimum conditions for deposition of SrTiO_3 films on Pt/Si and Ir/Si substrates were; T_b = 220 ℃ for Sr(tmhd)_2 and 60 ℃ for TTIP, T_2 = 550 ℃, carrier gas flow rates of 130 sccm for Sr(tmhd)_2 and 40 sccm for TTIP, oxygen flow rate of 130 sccm, and rf power of 160W. There is no clear difference in growth characteristics on the two substrates. The surface morphology examined by AFM and SEM showed a smooth surface and good adhesion at the interface. Based on the growth characteristics of films, the deposition mechanism of SrTiO_3 films was proposed. It was found that the deposition of SrTiO_3 films was limited by the decomposition rate of Sr(tmhd)_2 on the substrate surface.
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