Charge trapping effects in nonvolatile memory cells with HfO2/Al2O3 nanolaminated trapping layer

• Published in: Journal of physics. Conference series 2023-01, Vol.2436 (1), p.012016
• Main Authors: Spassov, D, Paskaleva, A, Guziewicz, E, Stanchev, T, Ivanov, Tz
• Format: Article
• Language: English
• Subjects: Aluminum oxide; Atomic layer epitaxy; Charge density; Computer memory; Electrons; Hafnium oxide; Illumination; Physics; Silicon dioxide; Stacks; Trapped charge; Trapping; Tunnels
• ISSN: 1742-6588; 1742-6596
• DOI: 10.1088/1742-6596/2436/1/012016

The charge trapping effects in memory cells with HfO2/Al2O3 nanolaminated stacks with two different thicknesses (2.4 and 3.5 nm) of the tunnel SiO2 layer were investigated. The HfO2/Al2O3 stacks were fabricated by atomic layer deposition and received post deposition annealing in O2. The structures with 3.5 nm tunnel oxide were found to provide higher density of trapped charges. The obtained trapped negative charge density is -3.56×10−6 C/cm2 and the positive one is 4.03×10−6 C/cm2. It is demonstrated that the electron trapping is significantly influenced by the amount of available electrons in the inversion layer. Under illumination, pulses with duration of 1 ms could provide trapped negative charge density equal to ~60% the value obtained at 10 s duration, where a saturation of the trapped charge is found. The hole trapping is not influenced by the illumination of capacitors and it is found to be slower than the electron one. Some aspects of the trapping process as well as some of the peculiarities in the capacitance-voltage curves obtained in the course of the measurements are briefly discussed.