Tailoring the Electrical Properties of HfO₂ MOS-Devices by Aluminum Doping

Abstract

In this work dielectric and electrical properties of Al-doped HfO2 layers deposited by plasma-enhanced atomic layer deposition in dependence on the thickness and the added Al amount in the films have been investigated. Special attention is dedicated to C-V and I-V hysteresis analysis as a measure for trapping phenomena in the films. A detailed study of conduction mechanisms in dependence on the composition of the layers has also been performed. The densities and spatial and energy positions of traps have been examined. It is found that only a small amount of Al-doping decreases the trapping which is assigned to a reduction of oxygen vacancy-related traps in HfO2. On the contrary, higher amounts of Al introduced in HfO2 films increase the trapping ability of the stacks which is due to the introduction of deeper Al2O3-related traps. The results imply that by adding a proper amount of Al into HfO2 it is possible to tailor dielectric and electrical properties of high-k layers toward meeting the criteria for particular applications.

Consideration of conduction mechanisms in high-k dielectric stacks as a tool to study electrically active defects

“…1.8 Fig. 22 logJ vs. logE hk curves representing the space-charge-limited conduction at low fields in HAHAH sample [52].…”

“…Three types of layers have been deposited on nitrided Si by atomic layer deposition (ALD)pure HfO 2 (75 cy), HfO 2 (36 cy)/Al 2 O 3 (5 cy)/HfO 2 (36 cy) (HAH), and HfO 2 (24 cy)/Al 2 O 3 (2 cy)/HfO 2 (24 cy)/Al 2 O 3 (2 cy)/HfO 2 (24 cy) (HAHAH). More details on deposition conditions and technology of structures could be found in [52]. Temperature dependent I-V measurements (Fig.…”

“…a) Representation of I-V curves in Poole coordinates (lnJ vs. E hk ) of HAHAH sample.The inset shows the dependence of activation energy E a =  t -s p E hk of Poole conduction on the electric field. (b) Arrhenius plot of the current in HAHAH sample in the whole temperature range (30-100° C) and for different applied voltages[52].…”

Atomic Layer Deposition and Properties of HfO2-Al2O3 Nanolaminates

“…[16][17][18] Al-doping in HfO 2 has been found useful when modifying defect densities and stoichiometry in dielectrics for MOS-devices. 19,20 Cubic and tetragonal polymorphs of HfO 2 knowingly possess higher dielectric permittivity compared to that of monoclinic phase, 21 and have thus been attractive for applications in capacitive memory devices and electronic switches. 22 The orthorhombic phase may also be considered as an interesting one in terms of electrical charge polarization, since, due to its noncentrosymmetric lattice, it could be responsible for the ability of the material to nonlinearly and saturatively polarize in external electric field.…”

Depth profiling of very thin HfO2/Al2O3 stacks by ellipsometry

“…As HfO2 is already being employed in the production of highperformance logical integrated circuits such as microprocessors, the opportunity of using the HfO2 technology in non-volatile memory applications is quite attractive. It has also been shown recently that the charge-trapping efficiency and retention characteristics of HfO2 can be substantially enhanced by incorporation of Al in its matrix, either by creating bi-layered stacks or by Al-doping [1,2]. Thus, (HfO2):(Al2O3) stacks have been considered as a promising candidate for the next generation of nonvolatile flash memories.…”