Temperature Dependence of the Current Conduction Mechanisms in Sm[sub 2]O[sub 3] Thin Films

Abstract

Metal-oxide-semiconductor capacitors with Sm 2 O 3 dielectric film were fabricated and the temperature dependence of the conduction mechanisms was studied. The Sm 2 O 3 films were deposited by radio frequency magnetron sputtering. The thickness of Sm 2 O 3 was 18.8 nm. The dielectric permittivity and the equivalent oxide thickness of capacitors with Sm 2 O 3 film were 15.0 and 4.8 nm, respectively. The X-ray photoelectron spectroscopy analysis showed a silicate interfacial layer formed between Sm 2 O 3 and Si. When the aluminum electrode was biased positive, the dominant conduction mechanism was Schottky emission in the temperature range 475 K Ͻ T Ͻ 500 K and at an electrical field of 0.8 MV/cm Ͻ E Ͻ 1.4 MV/cm. In the temperature range 300-425 K, the dominant conduction mechanism was most likely space-charge-limited conduction. When the aluminum electrode was biased negative, the dominant conduction mechanism in the temperature range from 325 to 500 K and at an electrical field from 0.08 to 0.81 MV/cm was Schottky emission. At 77 K and with the electrical field above 0.9 MV/cm, the conduction mechanism was Fowler-Nordheim ͑F-N͒ tunneling. The Al/Sm 2 O 3 electron barrier height and the effective electronic mass calculated from Schottky emission and F-N tunneling were 0.82 eV and 0.13 m 0 , respectively.Recently, many candidates such as tantalum oxide ͑Ta 2 O 5 ͒, 1 titanium dioxide ͑TiO 2 ͒, 2 aluminum oxide ͑Al 2 O 3 ͒, 3 zirconium ͑ZrO 2 ͒, 4-6 hafnium oxide ͑HfO 2 ͒, 4-8 dysprosium oxide ͑Dy 2 O 3 ͒, 9-12 and samarium oxide ͑Sm 2 O 3 ͒ have been introduced as alternative gate dielectrics. Among these high-k oxides, Sm 2 O 3 is a potential candidate to achieve high dielectric constant ͑12-13͒, large energy bandgap ͑4.33 eV͒, high thermal stability, and low leakage current density. [13][14][15][16] In the literature, Dakhel 17 observed Schottky emission at the Al/Sm 2 O 3 interface in Al/Sm 2 O 3 /Al devices and extracted a Schottky barrier of s = 0.85 eV. Rozhkov et al. 18 reported that the energy barriers at the Al/Sm 2 O 3 and the Si/Sm 2 O 3 interfaces extracted from internal photoemission of carriers were 2.89-2.91 and 2.70-2.72 eV, respectively. Yang and Xue 19 showed that the leakage current density of Sm 2 O 3 was 10 −4 A/cm 2 for an electric field of 0.24 MV/cm. However, there are relatively few reports on the temperature dependence of the conduction mechanisms with Sm 2 O 3 dielectric. In this work, the material properties were investigated by X-ray photoelectron spectroscopy ͑XPS͒ and transmission electron microscopy ͑TEM͒. The conduction mechanisms such as Schottky emission, Fowler-Nordheim ͑F-N͒ tunneling, and space-chargelimited conduction ͑SCLC͒ were also studied.Experimental p-Type, ͑100͒ orientation, 4 in. diameter silicon wafers with 5-10 ⍀ cm resistivity were used as the starting substrates. Following wafer cleaning, the Sm 2 O 3 films were deposited at room temperature by radio frequency magnetron sputtering in argon ͑Ar͒. The pressure of Ar gas during deposition was 5 ϫ 10 −3 Torr. The thic...

Material and electrical characterizations of high-k Ta2O5 dielectric material deposited on polycrystalline silicon and single crystalline substrate

“…Until now, studies have investigated different material compositions, processes and treatments for better electrical reliability, fewer interfacial states, and lower leakage current. In contrast to previous literature, this research studies the influence of substrate on dielectric performance [5][6][7]. Ta 2 O 5 dielectrics were sputtered on top of a polysilicon substrate in one group of samples, and on top of single crystalline substrate in another [8][9][10].…”