| Summary: | 博士 === 國立中山大學 === 電機工程學系研究所 === 93 === The dielectric constant of poly-crystalline titanium oxide (TiO2) films grown on silicon (Si) by metal organic chemical vapor deposition (MOCVD) is high. The leakage current is also high, which is dominated by the grain boundary and lower barrier height. Silicon oxide (SiO2) film is used as an interfacial layer for the structure of MOCVD-TiO2/SiO2/Si. The leakage current is much improved due to the high quality and high barrier height of SiO2/Si, but the total capacitance is lost due to the series of low-dielectric constant SiO2 films and amorphous low dielectric constant of TiO2 film grown on SiO2. Liquid-phase-deposited SiO2 is used as a cap layer for the structure of LPD-SiO2/MOCVD-TiO2/Si, the high dielectric constant of MOCVD-TiO2/Si is preserved. The leakage current is much improved due to the high barrier height SiO2 and the passivation of the dangling bonds of the grain boundary of poly-crystalline MOCVD-TiO2 films by the F from LPD-SiO2 films. Therefore, high dielectric constant and low leakage current LPD-SiO2/MOCVD-TiO2/Si films were obtained. Therefore, MOSFET with LPD-SiO2/MOCVD-TiO2 gate oxide can have lower off state leakage current, smaller subthreshold swing, higher transconductance, and higher field effect mobility.
On the other hand, LPD-SiO2/MOCVD-TiO2 film on (NH4)2Sx-treated InP not only can lower leakage current but can lower interface state density. The leakage current densities are 1.37×10-7 A/cm2 and 1.45×10-7A/cm2 under positive and negative electric fields at 1.5 MV/cm, respectively. The lowest interface state density is 4.7×1011 cm-2eV-1 in the band gap. Moreover, the dielectric constant can reach 61.2. Therefore, LPD-SiO2/MOCVD-TiO2 structure is a high dielectric constant and low leakage current film.
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