Scaling down of DRAM¡¦s dimensions is a continuous trend since its inception. Therefore, the high dielectric constant material is necessary because the application of conventional SiO2 will reach its physical limits. Due to TiO2 have high dielectric constant (£`// = 170, £`¡æ = 90), high refractive index (~2.5) and high chemical stability, it is a promising candidate for fabricating thin dielectrics in DRAM storage capacitors and as gate dielectrics of MOSFET without the problem of conventional SiO2 thickness scaling down in ULSI processes.
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 as precursors at the growth temperature which ranges from 400 oC to 650 oC. 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 film defect and the grain boundary. The electrical characteristics are also strongly associated with growth temperature. After oxygen annealing, the leakage current is improved due to the reduction of the oxygen vacancy of TiO2 film. However, the electrical characteristics can be further improved by the postmetallization annealing treatment especially under the negative electric field.
Post-metallization annealing (PMA) is an effective method in MOS technology to reduce the effective charge density and the interface state density. The mechanism of PMA is to use the reaction between the aluminum contact and hydroxyl groups existed on oxide surface to form active hydrogen and diffuse through the oxide to passivate the oxide traps. Therefore, MOCVD-TiO2/Si films which treated by O2-annealing and PMA with high dielectric constant and low leakage current can be obtained. The leakage current can reach 3.44¡Ñ10^-6 A/cm2 under a negative electric field of 5 MV/cm. The hysteresis loop shift voltage and the interface state densities are 5 mV and 1.17 ¡Ñ 10^11 cm−2 eV^−1, respectively.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0715105-105304 |
| Date | 15 July 2005 |
| Creators | Hung, Yu-Hsiang |
| Contributors | Jyi-Tsong Lin, Ming-Kwei Lee, Da-Ren Hang, I-Kai Lo |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0715105-105304 |
| Rights | withheld, Copyright information available at source archive |
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