Electrical Properties of TiO2 Thin Films on Si Substrate Prepared by MOCVD

• Main Authors: Wei-Cheng Chen, 陳維成
• Other Authors: Ming-Kwei Lee
• Format: Others
• Language: en_US
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/84611101409380412219

碩士 === 國立中山大學 === 電機工程學系研究所 === 91 === Recently, many dielectric materials have been considered as future promising candidates for a thin dielectric in DRAM storage capacitors. Due to its properties of high dielectric constant (ε// = 170, ε⊥ = 89), high refractive index (~2.5) and high chemical stability. TiO2 is a promising candidate for fabricating thin dielectrics in dynamic random access memory (DRAM) storage capacitors and as gate dielectrics of metal-oxide-semiconductor field effect transistor (MOSFET) without the problem of conventional SiO2 thickness scaling down in ULSI processes because of its high dielectric constant. TiO2 thin films grown on p-type (100) Si substrate are investigated by a cold wall horizontal MOCVD system using Ti(i-OC3H7)4, N2O and O2 as precursors in the growth temperature range from 400℃ to 700℃. The growth rate of using N2O as the oxidizer is quicker than the growth rate of using O2 as the oxidizer because N2O is the more efficient in producing free O atoms. XRD results indicate that the structures of TiO2 films are polycrystalline and the phase transformation temperature of TiO2 films from the anatase phase to the rutile phase is about 650℃. Electrical properties are strongly influenced by the growth temperature. The electrical properties of as-grown TiO2 films can be improved by annealing treatment. The TiO2 films using O2 as the oxidizer at the growth temperature of 600℃ has the highest dielectric constant of 119.3 and the lowest leakage current density of 1.43×10-6 A/cm2 at the applied electric field of 1 MV/cm after annealing for 20 minutes in O2. In order to obtain the better electrical properties of TiO2 films on Si substrate, we prepared TiO2 films by combination of MOCVD and LPD. The dielectric constant of post-annealed TiO2 films prepared by combination of MOCVD and LPD is 34.1. And the leakage current density of it is 3.7×10-6 A/cm2 at the applied electric field of 1 MV/cm. It is lower than the films prepared in the same MOCVD-TiO2 growth condition (about 8.2×10-6 A/cm2). It suggests that this growth method can reduce the leakage current density.