Effects of post deposition annealing atmosphere on interfacial and electrical properties of HfO2/Ge3N4 gate stacks

• Published in: Thin solid films 2019-04, Vol.675, p.16-22
• Main Authors: Mallem, Kumar, Jagadeesh Chandra, S.V., Ju, Minkyu, Dutta, Subhajit, Phanchanan, Swagata, Sanyal, Simpy, Pham, Duy Phong, Hussain, Shahzada Qamar, Kim, Youngkuk, Park, Jinjoo, Cho, Young-Hyun, Cho, Eun-Chel, Yi, Junsin
• Format: Article
• Language: English
• Subjects: Electrical properties; HfO2/Ge3N4/Ge interface; Interfacial properties; Metal oxide semiconductor devices; Post deposition annealing ambient
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2019.02.034

Effects of post deposition annealing (PDA) atmosphere, including oxygen (O2) gas and forming gas (FG), on interfacial and electrical properties of a HfO2 gate dielectric on nitrided Ge are analyzed. Experiments to study the dielectric morphology, interface quality, and chemical composition of HfO2/Ge3N4/Ge devices were carried out using X-ray diffraction, high-resolution transmission electron microscopy (HRTEM) imaging, and X-ray photoelectron spectroscopy (XPS) measurements, respectively. The XPS study confirmed that O2 PDA effectively improves the HfO2 film stoichiometry, and the stability of the interface between HfO2/Ge3N4/Ge stacks is enhanced. Further, HRTEM images showed that the interface between HfO2/Ge3N4/Ge stacks for O2-annealed devices was smooth, uniform, and flat. The experimental results for devices annealed in O2 at 500 °C exhibited improved interfacial and electrical characteristics, such as a high dielectric constant of ~19.50; high capacitance, 1.24 nF, low equivalent oxide thickness, 1.74 nm; interface trap density, 2.18 × 1011 cm−2 eV−1; oxide charges, 2.50 × 1012 cm−2; and gate leakage currents in the order nA of 0.5 × 10−9 A/cm2, as compared with FG annealing devices. The Fowler−Nordheim tunneling current conduction mechanism was also verified. Therefore, these results are evidence that the O2 PDA process improves the interfacial and electrical properties of HfO2/Ge3N4/Ge metal-oxide-semiconductor (MOS) devices as compared with FG annealing, which is important for future Ge-based complementary MOS device performance and reliability. •HfO2/Ge3N4 gate stacks were prepared on a germanium (Ge) substrate.•Ge3N4 was carried by rapid thermal processes at 575 °C in NH3 for 85 s.•The Ge3N4 layer acted as a sharp and clear interface between HfO2/Ge.•Effects of PDA with O2/FG on properties of HfO2/Ge3N4 stacks were analyzed.•PDA in O2-annealed devices exhibited improved structural, electrical, and interfacial properties.