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Synergic Impacts of CF4 Plasma Treatment and Post-thermal Annealing on the Nonvolatile Memory Performance of Charge-Trap-Assisted Memory Thin-Film Transistors Using Al–HfO2 Charge Trap and In–Ga–Zn–O Active Channel Layers

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journal contribution
posted on 07.03.2022, 12:03 authored by Jin-Ju Kim, Sung-Min Yoon
Charge-trap-assisted memory thin-film transistors (CTM-TFTs) using the engineered Al-doped HfO2 (Al:HfO2) CTL and In–Ga–Zn–O channel were fabricated and characterized to investigate the effects of CTL engineering processes including Al doping, CF4 plasma treatment, and thermal annealing on nonvolatile memory performances. The CTM-TFTs using the Al:HfO2 CTL treated with CF4 plasma and postannealing (A4) exhibited a wider memory window of 13.0 V with a gate voltage sweep range of ±20 V and a higher program/erase (P/E) ratio of 8.0 × 104 even with 1-μs-long P/E pulses. On the contrary, smaller memory windows were obtained to be 2.0, 3.5, and 4.5 V for the devices using the nontreated (A1), only CF4 plasma-treated (A2), and only thermally annealed Al:HfO2 CTLs (A3), respectively. Furthermore, for the A4 CTM-TFT device, the stable operational reliabilities including a long-term retention after a lapse of time for 104 s and a robust data endurance after repeated P/E cycles of 104 were obtained without any degradation of the P/E ratio. The improvement in memory device (A4) characteristics can be suggested to originate from the remarkable increase in the density of stable charge-trap sites located within the CTL and the effective suppression of undesirable trapping events in interfaces thanks to the optimum implementation of CTL engineering processes.