Detection of defect states responsible for leakage current in ultrathin tantalum pentoxide (Ta2O5) films by zero-bias thermally stimulated current spectroscopy

Abstract

Defect states responsible for leakage current in ultrathin (physical thickness <10 nm) tantalum pentoxide (Ta2O5) films were measured with a novel zero-bias thermally stimulated current technique. It was found that defect states A, whose activation energy was estimated to be about 0.2 eV, can be more efficiently suppressed by using N2O rapid thermal annealing (RTA) instead of using O2 RTA for postdeposition annealing. The leakage current was also smaller for samples with N2O RTA than those with O2 RTA for postdeposition annealing. Hence, defect states A are quite likely to be important in causing leakage current.

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

“…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 . It corresponds to the trap that has been attributed to the Si/Ovacancy complex shallow single donor (type A, 0.2 to 0.4 eV) [35]. Doted line corresponds to an idealized U-shaped distribution without peaks, with a flat part in the middle of the bandgap at about 2.210 12 eV -2 cm -2 .…”

Comparison of tunnel currents through SiO<inf>2</inf>, HfO<inf>2</inf>, Ta<inf>2</inf>O<inf>5</inf>, ZrO<inf>2</inf> and Dy<inf>2</inf>O<inf>3</inf> dielectrics in MOS devices for ultra large scale integration using first principle calculations

“…There occurs a decrease in the barrier height to the gate tunneling current with increasing dielectric constant of the gate oxide material. All these issues and technological constraints have led to the quest for new gate dielectric materials for future ultra-large scale integration (ULSI) devices with adequate diffusion barrier properties and high dielectric constant with better stability, tuned to the existing semiconductor process technology [1,7].…”

“…Such materials tend to disintegrate at high temperatures In addition, alternate CMOS process steps must be developed, including chemical and reactive ion etching of these materials. Therefore, the sub-100 nm silicon technology and deep sub-micron silicon technology would require not only the development of new gate materials but also complete re-engineering of CMOS manufacturing processes [1,7].…”

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

“…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.…”

“…Postdeposition anneal of Ta 2 O 5 samples was done by rapid thermal processing ͑RTP͒ in O 2 or N 2 O at 700-900°C at atmospheric pressure. 9 The sample under test was mounted onto a thin sheet of mica with silver paint. Then the mica sheet with the sample was mounted on the sample stage of the cryostat.…”