Characteristics of electron-beam-gun-evaporated Er2O3 thin films as gate dielectrics for silicon

Abstract

Structural properties of an ultrathin, 4.5 nm, erbium-oxide film and electrical properties of metal–oxide–semiconductor structure based on it are described. The evolution of the dielectric constant, total charge density, breakdown electric field, and leakage current density with annealing temperature in an oxygen environment are reported. The dielectric constant in the as-deposited state is relatively low, ∼7, possibly because the initial deposition forms ErO (with low polarizibility) rather than Er2O3. Annealing causes a transformation of ErO to Er2O3 but at the same time it initiates the growth of an interfacial SiO2 layer so that the effective dielectric constant is reduced to 5.5. Using the 4.5 nm film following annealing at up to 750 °C, we demonstrate an effective oxide thickness in the range 2.4–3.2 nm, with a leakage current density as low as 1–2×10−8 A/cm2 at an electric field of 106 V/cm and a breakdown electric field of 0.8–1.7×107 V/cm. A shift of the flat band voltage to the positive side and lowering of the total positive charge density down to 1012 cm−2 with annealing temperature are observed and can be explained by a charge compensation mechanism between the charges accumulated at the SiO2/Er2O3 and Si/SiO2 interface.

Superior electrical properties of crystalline Er2O3 films epitaxially grown on Si substrates

“…Other researchers have reported the value of fixed charge density from 8 ϫ 10 13 to 1 ϫ 10 10 cm −2 . 8,10,19 Based on our measurements, we have obtained that the maximum fixed charge density in our Er 2 O 3 thin film is less than 10 12 cm −2 . Figure 3͑b͒ shows the I-V curve of the Er 2 O 3 thin film with the MOS structure.…”

“…7 Among these materials, HfO 2 has been believed to be a promising high-k oxide in the near future. In general, rare earth ͑RE͒ oxides have relatively high dielectric constants, larger band gaps ͑ϳ5.4 eV͒, 8 higher conduction band offset with Si ͑over 2 eV͒, 9 and a good thermodynamic stability. 10 18 In recent years, Er 2 O 3 thin films grown on Si substrates were achieved in several groups with different techniques.…”

Optical and structural characterization of thermal oxidation effects of erbium thin films deposited by electron beam on silicon

“…For the first two sputter cycles, a shoulder peak (532.8 eV) can be seen at the higher energy side of the O 1 s line. This peak is attributed to the presence of hydrated erbium oxide, Er(OH) 3 , 24 due to interactions of the Er film with ambient moisture. As expected, peak intensity is significantly decreased as the surface layer is removed by ion sputtering.…”

“…In particular, erbium-based oxides are a promising candidate for high-k gate dielectrics in MOS devices. [2][3][4] Erbium oxide (Er 2 O 3 ) is characterized by a high dielectric constant (j ¼ 10-14), a wide bandgap (E g $ 5 eV), and is chemically inert with silicon. 4 Additionally, high-j dielectric materials, such as annealed Er-doped HfO 2 (15 at.…”

Electrochemical Synthesis of Rare Earth Ceramic Oxide Coatings

“…There is a long list of processing techniques for producing rare earth oxides including spray hydrolysis, pulsed laser deposition, chemical vapor deposition, solid state reactions, sol-gel method, and melt infiltration [19][20][21][22][23][24]. However, electrochemical synthesis has not been used extensively to deposit rare earth oxide coatings.…”