Nonvolatile Memory Effects of NiO Layers Embedded in Al2O3 High-k Dielectrics Using Atomic Layer Deposition

Nonvolatile Memory Effects of NiO Layers Embedded in Al2O3 High-k Dielectrics Using Atomic Layer Deposition
조원태이선숙정택모김창균안기석안재평이준영Jong-Won LeeJin-Ha Hwang
Issue Date
Electrochemical and solid-state letters
VOL 13, NO 6, H209-H212
Nanoscale nonvolatile memories have been gaining widespread attention in research and development because of the advent of digital convergent and ubiquitous societies. The next-generation nonvolatile memories should meet two prerequisites, i.e., faster programming/erasing speed and longer data retention time: 106 programming/erasing cycles, 10 years charge retention at 85°C, and 5 V or less programming voltage.1 Dynamic random access memories suffer from volatile data storage along with issues involving the scaling down of device structures and flash memories encountering variations in both operation voltages and oxide integrity. One alternative, polysilicon/oxide/nitride/oxide/Si SONOS devices, has been proposed as highly promising. Despite the continuous vertical scaling process, the SONOS structure suffers from two drawbacks, i.e., in terms of program/erase speed and charge retention. To improve the operation speed and charge retention features, replacing the blocking SiO2 layer and the conventional nitride trapping layer with high-k materials was attempted. The applications or modifications incorporate TaN/Al2O3/SiNx/SiO2/Si, metal gate/SiO2/high-k dielectrics/SiO2/Si, and metal nitride/high-k/high-k trapping layer/high-k/Si.2-4 Furthermore, tunnel barrier engineering was attempted using an ultrathin multiple layer instead of the SiO2 tunnel layer in the SONOS structure, where hole direct tunneling is suppressed.4-8 The charge-trapping memories require the artificial control conduction band offset between the tunnel layer and the charge-trapping layer to enhance the corresponding charge retention by reducing the trapped electron leakage from the charge-trapping layer. Tan et al. improved the retention issue using a hafnium oxide charge storage layer based on the energy band diagram.9
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