Hyoseok Song

Resistive switching of a TaOx/TaON double layer via ionic control of carrier tunneling

Resistance random access memory (RRAM) is an attractive candidate for future non-volatile memory due to its superior features. As the oxide thickness is scaled down, the charge transport mechanism is also subject to the transition from hopping to tunneling dominant process, which is critically related to the interfacial electronic band structure. A TaOx/TaON double layer-based RRAM is fabricated and characterized in this work. Upon TaON insertion at the lower interface, the improved switching behavior is observed. The TaON at the bottom electrode interface blocks oxygen vacancy percolation due to strong N-O bonds and also modifies interfacial band alignment to lower the injected electron energy from bottom electrode due to higher tunneling barrier height than that of TaOx/Pt. This study suggested that a defect-minimized insertion layer like TaON with a proper interfacial band alignment is pivotal in RRAM for the effective ionic control of carrier tunneling resulting in non-linear I-V behavior with improved properties.

Nonlinear and complementary resistive switching behaviors of Au/Ti/TaOx/TiN devices dependent on Ti thicknesses

The fabricated Au/Ti/TaOx/TiN devices demonstrate nonlinear behavior at a low resistance state and a complementary resistive switching (CRS) behavior that is dependent upon the thickness of the Ti insertion layer. The nonlinear behavior can be explained by the presence of an ultrathin TiOx layer that acts as a tunnel barrier. In addition, the CRS behavior can be understood in relation to the redistribution of oxygen vacancies between the Ti/TaOx top interfaces. A thicker Ti insertion layer forms a thicker TiOx layer at the Ti/TaOx interface, which can serve as another switching layer. The Au/Ti/TaOx/TiN devices in this study are fabricated with fully complementary metal-oxide-semiconductor-compatible materials and exhibit nonlinear behavior at a low resistance state and a CRS behavior that present possible solutions for the suppression of the sneak current in the crossbar arrays.

Stabilization of Ni conductive filaments using NH3 plasma treatment for electrochemical metallization memory

In this study, NH3 plasma treatment was utilized to enhance the resistive switching (RS) properties. Au/Ni/TaOx/NiSi and Au/Ni/NH3 plasma-treated TaOx/NiSi resistance RAM (RRAM) devices were fabricated and the resistive switching (RS) properties of these devices were subsequently investigated. Both RRAM devices exhibited conventional electrochemical metallization memory (ECM) behaviors. However, the NH3 plasma-treated samples exhibited improved resistance distribution compared with that of non-treated samples due to the remaining Ni conductive filaments (CF), even following a RESET process. Additionally, superior retention properties longer than 104 s were observed due to the formation of stable Ni CFs. The formation of a defect-minimized TaON layer, observed via X-ray photoelectron spectroscopy (XPS), could be the source of stability for the Ni CFs, resulting in improved device behavior for the NH3 plasma-treated samples.

Dielectric barrier characteristics of Si-rich silicon nitride films deposited by plasma enhanced atomic layer deposition

This work proposes a new method toward improving dielectric barrier characteristics through low dielectric permittivity (k) amorphous silicon nitride films (SiNx) deposited by plasma enhanced atomic layer deposition (PEALD). The dielectric constants of the atomic layer deposition (ALD) SiNx films were in the range of 4.25–4.71 and were relatively lower than that of SiNx deposited by plasma enhanced chemical vapor deposition (PECVD). The dielectric constants of the PEALD SiNx films were nearly identical to the values for PECVD silicon carbon nitride films (SiCN). Although the ALD SiNx films were low-k, they exhibited similar levels of film stress as PECVD SiNx, and the density of ALD SiNx film was higher than that of PECVD SiCN films. The ability to suppress copper (Cu) diffusion through 10-nm thick SiNx dielectric barriers in silicon dioxide/barrier/Cu/tantalum nitride structures on Si substrates was evaluated via Auger electron spectroscopy analysis. Although PEALD SiNx films possessed low dielectric con...