Oxygen migration in TiO2-based higher-k gate stacks

Abstract

Articles you may be interested inEngineering crystallinity of atomic layer deposited gate stacks containing ultrathin HfO2 and a Ti-based metal gate: Effects of postmetal gate anneal and integration schemes J. Vac. Sci. Technol. B 32, 03D122 (2014); 10.1116/1.4869162 Oxygen passivation of vacancy defects in metal-nitride gated HfO 2 / SiO 2 / Si devices Appl. Phys. Lett. 95, 042901 (2009); 10.1063/1.3186075 Stability of HfO 2 / SiO x / Si surficial films at ultralow oxygen activityWe report on the stability of high-permittivity ͑high-k͒ TiO 2 films incorporated in metal-oxide-silicon capacitor structures with a TiN metal gate electrode, focusing on oxygen migration. Titanium oxide films are deposited by either Ti sputtering ͓physical vapor deposition ͑PVD͔͒ followed by radical shower oxidation or by plasma-enhanced atomic layer deposition ͑PEALD͒ from titanium isopropoxide ͑Ti͕OCH͑CH 3 ͒ 2 ͖ 4 ͒ and O 2 plasma. Both PVD and PEALD films result in near-stoichiometric TiO 2 prior to high-temperature annealing. We find that dopant activation anneals of TiO 2 -containing gate stacks at 1000°C cause 5 Å or more of additional SiO 2 to be formed at the gate-dielectric/Si-channel interface. Furthermore, we demonstrate for the first time that oxygen released from TiO 2 diffuses through the TiN gate electrode and oxidizes the poly-Si contact. The thickness of this upper SiO 2 layer continues to increase with increasing TiO 2 thickness, while the thickness of the regrown SiO 2 at the gate-dielectric/Si interface saturates. The upper SiO 2 layer degrades gate stack capacitance, and simultaneously the oxygen-deficient TiO x becomes a poor insulator. In an attempt to mitigate O loss from the TiO 2 , top and bottom Al 2 O 3 layers are added to the TiO 2 gate dielectric as oxygen barriers. However, they are found to be ineffective, due to Al 2 O 3 -TiO 2 interdiffusion during activation annealing. Bottom HfO 2 / Si 3 N 4 interlayers are found to serve as more effective oxygen barriers, reducing, though not preventing, oxygen downdiffusion.

Electrical Properties of Ultrathin Hf-Ti-O Higher k Gate Dielectric Films and Their Application in ETSOI MOSFET

“…As for TiO 2 , oxygen migration leads to oxygen vacancies [21], the common defects in TiO 2 . Oxygen vacancies decrease the resistivity of TiO 2 , which makes TiO 2 an n-type semiconductor [22, 23].…”

Extremely Scaled (∼0.2 nm) Equivalent Oxide Thickness of Higher-k (k = 40) HfO2 Gate Stacks Prepared by Atomic Layer Deposition and Oxygen-Controlled Cap Post-Deposition Annealing

“…This means that, for further EOT scaling, further enhancement of the permittivity of high-k dielectrics (higher-k) would be a possible solution. [8][9][10][11][12][13][14][15][16][17][18][19][20][21] In our previous study, we developed an oxygen-controlled cap post-deposition annealing (cap-PDA) technique, which realized a higher-k HfO 2 gate stack without a SiO 2 IL. 19,21) A high-permittivity ''cubic'' phase HfO 2 was generated by abrupt and short-time annealing with a Ti capping layer.…”

Damage Characteristics of TiO2 Thin Film Surfaces Etched by Capacitively Coupled Radio Frequency Helium Plasmas

“…TiO 2 thin film is also considered as one of the MOS gate dielectric material candidates. 4,5) This is because TiO 2 has a high dielectric constant (30-170) and an excellent thermal stability, which results in a decrease in the gate leakage current. However, there are lots of issues in fabrication processes of MOS device with the TiO 2 gate dielectric because TiO 2 is a binary compound.…”