HfO₂/Al₂O₃Bilayered High-kDielectric for Passivation and Gate Insulator in 4H-SiC Devices

Abstract

The electrical and chemical properties of high-k dielectric stacks consisting of Hafnium oxide (HfO 2 ) and Aluminum oxide (Al 2 O 3 ) deposited on 4H-SiC have been investigated by preparing metal insulator semiconductor (MIS) structures of HfO 2 /Al 2 O 3 /SiC. The bilayer gate stack was deposited by using atomic layer deposition (ALD). The samples were also treated by rapid thermal annealing (RTA) at 970 • C for 5 mins in an inert gas atmosphere. Structural properties of the deposited films were analyzed with X-ray diffraction (XRD), atomic force microscopy (AFM) and Rutherford backscattering spectroscopy (RBS). Capacitance-voltage (CV) measurements performed on as-deposited and RTA treated structures at room temperature show that the RTA treatment increases the effective oxide charges in the whole dielectric but decreases the interface trap density. Current-voltage (IV) measurements have been performed in order to extract the leakage current density as well as the breakdown characteristics of the stack. Our results show that a combination of HfO 2 and Al 2 O 3 can be a better choice for SiC than individual Al 2 O 3 layer because of the higher value of effective dielectric constant. It is shown that the stacked dielectrics are stable at high temperatures and under annealing conditions up to 300 • C, which makes the layers compatible with SiC device processing and higher operating temperatures compared to silicon.

Influence of annealing environment on the ALD-Al2O3/4H-SiC interface studied through XPS

“…In recent years, the main focus in alternate dielectric search was on interface stability, easy process integration, and di electric constant value. The dielectrics investigated for this purpose are Al 2 O 3 [5][6][7], AlN [8], HfO 2 [9,10], Ta 2 O 5 [11], TiO 2 , etc and combinations of one or two dielectrics in layered form [9,14], as well as mixed form such as aluminum oxynitride (AlON) [15], Hf x Ti 1−x O 2 and Hf x Ti 1−x ON [13,16,17]. It is particularly important to note that most of the stacked and mixed dielectric efforts were made by adding thin SiO 2 as a first layer interfacing with 4H-SiC [18].…”

Structural and Insulating Behaviour of High-Permittivity Binary Oxide Thin Films for Silicon Carbide and Gallium Nitride Electronic Devices

“…In summary, among the pure high-κ oxides, Al 2 O 3 thin films represent the best compromise, especially in combination with a very thin SiO 2 interfacial layer. Some possible other high-κ bilayers, such as HfO 2 /Al 2 O 3 [64], Y 2 O 3 /Al 2 O 3 [65], or ZrO 2 /SiO 2 [66], exhibited some potentiality, although not many reports have been made available to date, especially regarding devices.…”

Improvement of self-heating effect in Ge vertically stacked GAA nanowire pMOSFET by utilizing Al2O3 for high-performance logic device and electrical/thermal co-design

“…This can cause a I gate issue. Fortunately, the higher bandgap of Al 2 O 3 (7.0 eV) (see bandgap of HfO 2 : 5.6 eV) 40) can act as a buffer to alleviate this issue. In this section, the I gate issue will be discussed with a detailed explanation.…”