Trapping mechanism of charge trap capacitor with Al2O3/High- k/Al2O3 multilayer

Charge trap flash memories with Al2O3/High-k/Al2O3 multilayer have been considered to reduce leakage current and improve electrical properties under low operation voltage for further device scaling down capability [1, 2]. In case of charge trap capacitor with SiO2/SiN/Al2O3 multilayer, the several mechanism have been proposed to recognize where injected electron is trapped. For example, the injected electrons are piled up in a center of SiNcharge trap layer (SiN-CTL) or interface between SiO2 tunneling layer (TL) and SiN-CTL or other interface between SiN-CTL and Al2O3-blocking layer (AlO-BL) [3]. However, the trapping mechanism of the High-k-charge trap layer (High-k-CTL) is still not clear. In this paper, we focus on the trapping mechanism of High-k-CTLs, such as an amorphous (Ta/Nb)Ox (TNO-CTL), a crystallized ZrO2 (ZrO-CTL) and a ferroelectric HfZrOx (HZO-CTL), from the data of flatband voltage (Vfb) characteristics under program mode. Pt-gated charge trap capacitors with Al2O3/(Ta/NbOx)/Al2O3 (ATNA), Al2O3/ZrO2/Al2O3 (AZA), and Al2O3/HfZrOx/Al2O3 (AHZA) were prepared by atomic layer deposition and annealing processes. The thicknesses of the TNO, ZrO and HZO-CTLs were varied from 5 to 20 nm while Al2O3-tunneling layer (AlO-TL) and AlO-BL were kept to be 8 nm thickness. Please click Additional Files below to see the full abstract

Invited - Characteristics of oxide TFT using atomic-layer deposited InOx-based metal oxide channel

InOx-based metal oxide semiconductors (InOx-OSs) including In-Ga-Zn-O (IGZO) [1,2] have been investigated as active channel materials in oxide thin film transistors (TFTs) for flat-panel display applications. These InOx-OSs have recently attracted attention for n-channel field effect transistor (n-FET) in back-end of line [3-5] and ferroelectric FET with HfO2-based ferroelectric gate insulator [6] First, InOx-OS films were deposited vis sputtering method. Considering to the growth of ultra-thin films, atomic layer deposition (ALD) technique is of great interest in the angstrom-scale thickness controllability, atomically smooth surface and composition control of multicomponent films as well as excellent step coverage on three-dimensional structure. The superior transistor performance of TFTs with ALD-In2O3 and IGZO channels and n-FET with ALD-In2O3 channel have been demonstrated [3,4,7]. Here, In2O3 films have been deposited via ALD with a combination of various precursors and oxidant gases such as trimethyl indium-O2, O3, H2O, or H2O2, and ethylcycropentadienyl indium (InEtCp)-H2O/O3 [8-10]. Please click Download on the upper right corner to see the full abstract

Vacancy-type defects in Al2O3/GaN structure probed by monoenergetic positron beams

Defects in the Al2O3(25 nm)/GaN structure were probed by using monoenergetic positron beams. Al2O3 films were deposited on GaN by atomic layer deposition at 300 °C. Temperature treatment above 800 °C leads to the introduction of vacancy-type defects in GaN due to outdiffusion of atoms from GaN into Al2O3. The width of the damaged region was determined to be 40–50 nm from the Al2O3/GaN interface, and some of the vacancies were identified to act as electron trapping centers. In the Al2O3 film before and after annealing treatment at 300–900 °C, open spaces with three different sizes were found to coexist. The density of medium-sized open spaces started to decrease above 800 °C, which was associated with the interaction between GaN and Al2O3. Effects of the electron trapping/detrapping processes of interface states on the flat band voltage and the defects in GaN were also discussed