Charge Trapping and TDDB Characteristics of Ultrathin MOCVD $\hbox{HfO}_{2}$ Gate Dielectric on Nitrided Germanium

Abstract

In this letter, we investigate the long-term reliability characteristics of ultrathin HfO 2 dielectrics on nitrided germanium for the first time. Stress-polarity dependence in charge trapping and time-dependent dielectric-breakdown (TDDB) characteristics has been observed in germanium n-and p-type devices. The p-MOS devices exhibit severe charge trapping under stress, while no significant charge trapping and stress-induced leakage current were found in the n-MOS devices. In terms of operationvoltage projection for a ten-year lifetime, V g = 2.8 and −2.1 V is projected for the germanium p-and n-MOS devices, respectively, with an equivalent oxide thickness of 11 Å. Compared to Si control samples, germanium devices show a comparable projected operation voltage, indicating that the TDDB for high-κ dielectrics on nitrided germanium is not a concern. The stress-polarity dependence in germanium devices is believed to result from the asymmetrical band structure and the significant difference of the electric field strength across the gate dielectric between the positive and negative stress conditions. Index Terms-Ammonia treatment, germanium, hafnium oxide, high-κ dielectric, MOS, reliability, time-dependent dielectric breakdown (TDDB).

Germanium surface passivation and atomic layer deposition of high-kdielectrics—a tutorial review on Ge-based MOS capacitors

“…Many approaches were investigated to form a stable and desirable IL with Ge surface nitridation. One of the most frequently used methods was thermal NH 3 treatment at various temperatures [12,[29][30][31][32][33][34][35][36]. Single GeO x N y [29,32] or Ge 3 N 4 [37] layers were attempted as gate dielectrics.…”

“…Single GeO x N y [29,32] or Ge 3 N 4 [37] layers were attempted as gate dielectrics. However, since they possess a rather low k value, more reports were using GeO x N y [30,31,[33][34][35] or GeN x [38,39] as a passivation layer, with another higher k dielectric on top. Otani et al reported a low D it of 4 × 10 11 eV −1 cm −2 at midgap using a 2 nm thick GeN x passivation layer [38], while a lower D it of 1.8 × 10 11 eV −1 cm −2 was demonstrated with a slightly thicker (∼2.4 nm) GeN x IL [39].…”

Novel Sn-assisted nitridation of Ge/HfO2 interface and improved electrical properties of the MOS capacitor

“…The nitridation of Ge surfaces prior to high-k film deposition is one of the best-known solutions because it is effective in suppressing Ge diffusion in metal oxides and leads to improved performance of Ge-based devices. [4][5][6][7][8][9][10][11] Annealing in NH 3 ambient is widely used for Ge surface nitridation and the formation of the GeON interface layer. [6][7][8][9][10] However, these methods for introducing the nitrogen element always involve high-temperature treatment above 550 °C.…”

“…[4][5][6][7][8][9][10][11] Annealing in NH 3 ambient is widely used for Ge surface nitridation and the formation of the GeON interface layer. [6][7][8][9][10] However, these methods for introducing the nitrogen element always involve high-temperature treatment above 550 °C. Since a clean Ge surface without any incorporation of oxygen is totally inert to NH 3 at temperatures up to 600 °C, 12) high-temperature treatment would result in nitrogen accumulation at the Ge/GeON interface, resulting in deterioration of the interface properties.…”