Silicon diffusion control in atomic-layer-deposited Al2O3/La2O3/Al2O3 gate stacks using an Al2O3 barrier layer

Abstract

In this study, the physical and electrical characteristics of Al2O3/La2O3/Al2O3/Si stack structures affected by the thickness of an Al2O3 barrier layer between Si substrate and La2O3 layer are investigated after a rapid thermal annealing (RTA) treatment. Time of flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS) tests indicate that an Al2O3 barrier layer (15 atomic layer deposition (ALD) cycles, approximately 1.5 nm) plays an important role in suppressing the diffusion of silicon atoms from Si substrate into the La2O3 layer during the annealing process. As a result, some properties of La2O3 dielectric degenerated by the diffusion of Si atoms are improved. Electrical measurements (C-V, J-V) show that the thickness of Al2O3 barrier layer can affect the shift of flat band voltage (VFB) and the magnitude of gate leakage current density.

Advances in La-Based High-k Dielectrics for MOS Applications

“…LaYO [37], LaTaO [41]), and addition of an interfacial passivation layer (e.g. Al2O3 [27]). However, because of the trade-off between the k value and the dielectric/semiconductor interface quality, there is still ample room to improve the device performance…”

“…For many years, in order to decrease the defect density of the La 2 O 3 gate dielectric, many efforts have been made, including high-temperature annealing, N incorporation, F or NH 3 treatment, doping other high-k metal elements to form complex oxides (e.g. LaYO [37], LaTaO [41]), and addition of an interfacial passivation layer (e.g., Al 2 O 3 [27]). However, because of the trade-off between the k value and the dielectric/semiconductor interface quality, there is still ample room to improve the device performance…”

“…However, the uncertainty in the phase of perovskite oxide is still limiting the performance of relevant MOS devices. Then, rare-earth oxide as a high-k dielectric has been studied, and La2O3 is a representative that has attracted much attention in recent years due to its high k value (~27) [27], large band gap (5.8~6.0 eV) [28], high breakdown field (> 13 MV/cm) [29], low leakage current for small effective oxide thickness (EOT) [30], good thermodynamic stability, and good high-field reliability on Si [30,31]. Based on the WKB approximation, the direct tunneling currents of ideal MOS structures with different dielectrics were modeled and simulated by H. Wu, et al, with results demonstrated in Figure 4 [32].…”

“…So, based on the advantages of La2O3 over other high-k materials and with the motivation of providing guidelines for making good use of La-based high-k materials to improve the performance of MOS devices for meeting the requirements of the technology nodes in the future, this review focuses on the advances of La-based high-k dielectrics in MOS applications. To have a better understanding of the characteristics of the La-based films; the basic theories for the main concerns of La2O3 as gate dielectric and the proposed solutions to these problems are discussed in section 2, including the hygroscopicity Then, rare-earth oxide as a high-k dielectric has been studied, and La 2 O 3 is a representative that has attracted much attention in recent years due to its high k value (~27) [27], large band gap (5.8~6.0 eV) [28], high breakdown field (> 13 MV/cm) [29], low leakage current for small effective oxide thickness (EOT) [30], good thermodynamic stability, and good high-field reliability on Si [30,31]. Based on the WKB approximation, the direct tunneling currents of ideal MOS structures with different dielectrics were modeled and simulated by H. Wu, et al, with results demonstrated in Figure 4 [32].…”

Effects of Rapid Thermal Annealing and Different Oxidants on the Properties of LaxAlyO Nanolaminate Films Deposited by Atomic Layer Deposition

“…The replacement of SiO 2 with high dielectric constant ( k ) materials has recently attracted considerable attention because their large physical thickness can suppress a gate tunneling leakage current at a scaled equivalent oxide thickness (EOT) [1–4]. Several candidate materials for the gate dielectric films such as HfO 2 [5], ZrO 2 [6], La 2 O 3 [7], Y 2 O 3 [8], Ta 2 O 5 [9], and Al 2 O 3 [10] have been studied extensively during the past decade. As a promising high- k material, La 2 O 3 has advantages of high dielectric constant (~30) and good thermal stability, but the hygroscopicity would lead to high leakage [11].…”