Detection of oxygen vacancy defect states in capacitors with ultrathin Ta2O5 films by zero-bias thermally stimulated current spectroscopy

Abstract

Defect state D (0.8 eV) was experimentally detected in Ta2O5 capacitors with ultrathin (physical thickness <10 nm) Ta2O5 films using zero-bias thermally stimulated current spectroscopy and correlated with leakage current. Defect state D can be more efficiently suppressed by using N2O rapid thermal annealing (RTA) instead of using O2 RTA for postdeposition annealing and by using TiN instead of Al for top electrode. We believe that defect D is probably the first ionization level of the oxygen vacancy deep double donor. Other important defects are Si/O-vacancy complex single donors and C/O-vacancy complex single donors.

HYSTERESIS-LIKE FLATBAND VOLTAGE INSTABILITIES IN Al/Ta2O5-SiO2/Si STRUCTURES AND THEIR CONNECTION WITH J-V CHARACTERISTICS

“…Practically the same value (0.7 eV) was found in [32] for the electron trapping centres responsible for the leakage currents in Ta 2 O 5 . This value is close to the value of the activation energy of the traps of type D (0.8 eV), found in [33] using zero-bias thermally stimulated current spectroscopy and attributed to the first ionization level of the double-donor oxygen vacancy and later theoretically explained in [34]. The second much broader peak is located at approximately 0.9 eV from the valence band of silicon, which corresponds to approximately 0.3 eV from the conduction band of Ta 2 O 5 .…”

Effects of the post-annealing ambience on the microstructure and optical properties of tantalum oxide films prepared by pulsed laser deposition

“…Tantalum pentoxide (Ta 2 O 5 ) has rapidly evolved as a potentially important film material in a wide range of industrial applications such as optical coatings [1], dielectric films [2], and corrosion [3] and heat-resistant coatings [4]. For instance, it has a high refractive index (n∼2.2 at 633 nm wavelength), a large band gap (E g ∼4.2 ev), almost free-absorption between 300 nm and 2.0 m [5], making it as an important potential material in optical applications as anti-reflective or high-reflective film mirrors for solar cells, and high power laser equipments [6][7][8].…”

Application of zero-temperature-gradient zero-bias thermally stimulated current spectroscopy to ultrathin high-dielectric-constant insulator film characterization

“…13 Recently, we pointed out that defect A is probably a Si-O vacancy complex. 10,18 As shown in Fig. 5, using our old approach, there is a thermoelectric parasitic current rising with temperature and switching sign at about 270 K and then rising with temperature in the other direction.…”

“…Previously, we proposed that defect D may be the first ionization level of the oxygen vacancy double donor. 10 In addition, we pointed out that defect D can be difficult to detect because of ͑1͒ its relatively high peak temperature and ͑2͒ its poor carrier capture rate because it has an electron-repulsive energy barrier. 19,20 Using our approach proposed in this letter, it is much easier to detect defect D because of the suppression of the thermoelectric parasitic current.…”

“…It can be easily seen that the sensitivity of the TSC technique can be significantly improved by eliminating the bias voltage applied to the sample during TSC measurement, resulting in the zero-bias thermally stimulated current ͑ZBTSC͒ technique, which has been used by us on Ta 2 O 5 thin films. 6,[8][9][10] The driving force for the electrons or holes during ZBTSC can be due to a built-in electric field or a temperature gradient. 11 A built-in electric field exists in many types of semiconductor device structures, for example, p-n junctions, Schottky barriers, metal-insulator-semiconductor ͑MIS͒ diodes, etc.…”