Charge trapping and reliability characteristics of sputtered Y₂O₃high-kdielectrics on N- and S-passivated germanium

Abstract

We demonstrate the potential of sulfur passivation to improve the interface characteristics between germanium (Ge) and Y 2 O 3 high-k gate dielectric. Effects of nitrogen (N) and sulfur (S) passivation of the Ge surface on the charge trapping and reliability properties of Y 2 O 3 /Ge gate stacks are studied in detail and the results are compared. Sulfur passivation of the Ge surface has been performed using both the wet sulfidation technique with aqueous ammonium sulfide and plasma sulfidation with H 2 S gas. N-passivation of Ge substrates has been performed in NO plasma for comparison. Ultrathin (∼15 nm) Y 2 O 3 films are deposited on both the N-and S-passivated p-Ge (1 0 0) wafers. Y 2 O 3 films on the S-passivated Ge surface show low fixed oxide charge and interface state density than what is achieved with N-passivation. The electrical characterization results of MOS capacitors with Y 2 O 3 films reveal the potential of S-passivation for the fabrication of Y 2 O 3 /Ge gate stacks for Ge MOSFETs.

Dielectric relaxation of high-k oxides

“…Among them are cerium oxide CeO 2 [16-23], cerium zirconate CeZrO 4 [24], gadolinium oxide Gd 2 O 3 [25-27], erbium oxide Er 2 O 3 [28,29], neodymium oxide Nd 2 O 3 [30,31], aluminum oxide Al 2 O 3 [32,33], lanthanum aluminum oxide LaAlO 3 [34,35], lanthanum oxide La 2 O 3 [36], yttrium oxide Y 2 O 3 [37], tantalum pentoxide Ta 2 O 5 [38], titanium dioxide TiO 2 [39], zirconium dioxide ZrO 2 [40,41], lanthanum-doped zirconium oxide La x Zr 1 −x O 2 −δ [42,43], hafnium oxide HfO 2 [44], HfO 2 -based oxides La 2 Hf 2 O 7 [45], Ce x Hf 1-x O 2 [46], hafnium silicate HfSi x O y [47], and rare-earth scandates LaScO 3 [48], GdScO 3 [49], DyScO 3 [50], and SmScO 3 [51]. Among them, HfO 2 , HfO 2 -based materials, ZrO 2 , and ZrO 2 -based materials are considered as the most promising candidates combining high dielectric permittivity and thermal stability with low leakage current due to a reasonably high barrier height that limits electron tunneling.…”

Electronic Structure and Optical Quality of Nanocrystalline Y2O3 Film Surfaces and Interfaces on Silicon

“…Oxide dielectrics have been the subject of numerous investigations for many years due to their possible device integration in a wide range of technologies involving electronics, electro-optics, optoelectronics, and magneto-electronics. − Yttrium oxide (Y 2 O 3 ), a stable oxide of yttrium metal, has received significant attention in recent years in view of its possible integration into a wide range of scientific and technological applications. − Y 2 O 3 films exhibit excellent electronic properties such as transparency over a broad spectral range (0.2–8 μm), high dielectric constant (∼14–18), high refractive index (∼2), large band gap (∼5.8 eV), low absorption (from near-UV to IR), and superior electrical breakdown strength (>3 MV/cm). ,− ,− These properties make Y 2 O 3 films interesting for various electrical and optical devices. − Yttrium oxides were proposed as hosts for rare-earth elements, and efficient thin film phosphors were prepared. − The interface layer formation, however, was detected for several compounds, and structural and chemical parameters of the interface were dependent on the deposition conditions. Therefore, controlled growth and manipulation of microstructure, particularly at the nanoscale dimensions, has important implications for the design and applications of Y 2 O 3 films.…”

S-Passivation of the Ge Gate Stack Using (NH₄)₂S

“…Some work has been published on the Spassivation of Ge by (NH 4 ) 2 S [2,3] but the passivation of the gate stack has not been addressed in these references. Recently, some work has been reported on S-passivation by (NH 4 ) 2 S of the gate stack [4,5]. In this work, we will present the results of the S-passivation of the Ge gate stack by using (NH 4 ) 2 S.…”