Characterization of La[sub 2]O[sub 3] and Yb[sub 2]O[sub 3] Thin Films for High-k Gate Insulator Application

Abstract

Rare earth oxides, such as La2O3 and Yb2O3, deposited on Si(100) were investigated for high-k gate insulator applications. La2O3 has the largest bandgap and smallest lattice energy among the rare earth oxides, while Yb2O3 has a smaller bandgap and larger lattice energy compared to La2O3. La2O3 showed excellent electrical properties, such as small capacitance equivalent thickness and low leakage current density with smooth film surface and interface after rapid thermal annealing (RTA) at 400-600°C. On the other hand, the surface of Yb2O3 thin film was easily roughened after RTA even at 400°C, and the leakage current density was higher compared to La2O3. The difference in characteristics for the films was considered to be attributed to the difference of their properties, such as bandgap and lattice energy. La2O3 was able to keep the amorphous phase at least up to 600°C RTA, and this seems promising for future high-k gate insulator applications. © 2003 The Electrochemical Society. All rights reserved.

Tunneling in sub-5nm La2O3 films deposited by E-beam evaporation

“…In this regard, transmission electron microscopy (TEM) studies combined with medium energy ion scattering analysis performed on atomic beam deposited La 2 O 3 films, have revealed that the composition of this material is far from uniform with significant penetration of silicon into the films from the substrate [5]. Similar results, pointing out the formation of interfacial lanthanum silicate (La x Si 1Àx O y ) layers, have been reported by Jun et al [4] using X-ray photoelectron spectroscopy and by Ohmi et al [6] using TEM images. Moreover, reliability studies have also demonstrated that the presence of weak spots in high-K dielectric films is common in such materials [7].…”

“…Even though the electron transport properties of La 2 O 3 films were investigated in the past, the reported results are mostly qualitative [4,6,17,19] or limited in voltage [16]. To our knowledge, no report exists concerning the simulation of the direct and Fowler-Nordheim regimes in such material.…”

Rare-earth oxide thin films for gate dielectrics in microelectronics

“…Achievement of epitaxy in Pr 2 O 3 films on Si(1 0 0) and Si(1 1 0) may occur complicated [24], but has been realized at 675 • C by MBE [26]. La 2 O 3 has the lowest and Lu 2 O 3 has the highest lattice energy −12.687 and −13.871 kJ/mol, respectively [27,28]. The energy of band gap is the highest in La 2 O 3 (5.5 eV) and lowest in Lu 2 O 3 (4.9 eV).…”

“…The EOT and leakage currents for several oxides grown by MBE on Si have been studied by Iwai et al [40], and La 2 O 3 has been recognized as the material with the thinnest interface oxide, very stable C-V characteristic, very low leakage current, high resistance to the crystallization and superior smoothness. Superior performance of La 2 O 3 has been attributed to its wide band-gap and the lowest lattice energy [42]. Jun et al have shown that MOCVD based on La(thd) 3 -tetraglyme results in La 2 O 3 films of slightly higher permittivity and lower leakage compared to La(thd) 3 and La(thd) 3 -TETEA [108].…”

DC-conduction mechanism in crystalline oxidised La and La–Mn films grown on p-Si substrate

“…Furthermore, lanthana thin-film insulators have excellent low leakage currents; 10 −4 to 10 −7 A/cm 2 at about 1 MV/cm [6,7,[9][10][11][12]. However, it is important to know the detailed conduction mechanism in La 2 O 3 films to ensure their reliability.…”