Efficient Detection of Oxygen Vacancy Double Donors in Capacitors with Ultra-thin Ta₂O₅ Films for DRAM Applications by Zero-bias Thermally Stimulated Current Spectroscopy

Abstract

Previously, defect D (V O + ) was barely detected in ultra-thin (physical thickness < 10 nm) Ta 2 O 5 capacitors for DRAM applications using zero-bias thermally stimulated current (ZBTSC) spectroscopy and correlated with leakage current. Our explanation is that defect D (V O + ) behaves like an electron trap with an electron-repulsive energy barrier and thus small electron capture cross section at low temperature such that it is difficult for defect D to capture electrons during ultraviolet illumination at low temperature. We modified our experimental technique to a twoscan ZBTSC technique and managed to detect oxygen vacancies much more efficiently in ultrathin Ta 2 O 5 films for the first time. Two-scan ZBTSC can also be applied to other high-K dielectric materials for process diagnosis.

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

“…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.…”