Effects of annealing conditions on optical and electrical characteristics of titanium dioxide films deposited by electron beam evaporation

Abstract

We report measured evolutions of the optical band gap, refractive index, and relative dielectric constant of TiO2 film obtained by electron beam gun evaporation and annealed in an oxygen environment. A negative shift of the flat band voltage with increasing annealing temperatures, for any film thickness, is observed. A dramatic reduction of the leakage current by about four orders of magnitude to 5×10−6 A/cm2 (at 1 MV/cm) after 700 °C and 60 min annealing is found for films thinner than 15 nm. An equivalent SiO2 thickness of the order of 3–3.5 nm is demonstrated. An approach is presented to establish that at different ranges of applied voltage the hopping, space charge limited current, and Fowler–Nordheim are the basic mechanisms of carrier transport into the TiO2 film.

The structural and electrical properties of thermally grown TiO2thin films

“…• C in O 2 for 60 min [10]. From figure 12, it is clear that leakage currents in our thermally grown TiO 2 thin films are very similar to those in the post-growth annealed oxide layers.…”

“…Figure 11 compares the I -V characteristics of our thermally grown TiO 2 with those of as-deposited oxide layers grown by other techniques [8][9][10]. It is observed that the leakage current in the thermally grown TiO 2 is about three orders of magnitude lower than that in plasma-oxidized TiO 2 [8] and in e-beam deposited TiO 2 [10]. At low bias, thermally grown TiO 2 also has a lower leakage current than in PECVD-grown TiO 2 [9].…”

“…Various techniques are used to grow TiO 2 , e.g. plasma oxidation [8], plasma-enhanced chemical vapour deposition (PECVD) [9], direct electron-beam evaporation [10] and metal organic chemical vapour deposition (MOCVD) [11]. The metal oxide semiconductor (MOS) capacitor structure is of fundamental importance for device application of TiO 2 thin films grown on Si substrates.…”

A highly sensitive evaluation method for the determination of different current conduction mechanisms through dielectric layers

“…As already mentioned, the difference between the leakage current conduction mechanisms for the studied sample in accumulation and in inversion can be explained, respectively, by the plasma process induced damage of the SiO 2 surface and the surface near the bulk region during gate metal formation. 13 Most probable, Ti is reacting during FGA with oxygen, resulting in oxygen deficiencies in the SiO 2 near the gate electrode that represent traps for charge carriers. In accumulation, the created traps act as traps for PF emission, resulting in multiple current conduction mechanisms (i.e., FN tunneling and PF emission).…”

“…However, they could not evaluate and model their measurement data for the whole voltage range consistently. 13 In this paper, the current conduction mechanisms for conventional MOS capacitors with SiO 2 layers, for which the possible conduction mechanisms are well known, are investigated by means of a-voltage (a-V) plots using, for the first time, successfully physical meaningful PF and FN modeling to demonstrate the potential of the method. The presented results suggest that the a-V plot is a very sensitive evaluation method for the current conduction mechanisms of dielectric films.…”