Relaxation Behavior and Breakdown Mechanisms of Nanocrystals Embedded Zr-doped HfO2 High-k Thin Films for Nonvolatile Memories

Abstract

Semiconducting or metallic nanocrystals embedded high-k films have been investigated. They showed promising nonvolatile memory characteristics, such as low leakage currents, large charge storage capacities, and long retention times. Reliability of four different kinds of nanocrystals, i.e., nc- Ru, -ITO, -Si and -ZnO, embedded Zr-doped HfO2 high-k dielectrics have been studied. All of them have higher relaxation currents than the non-embedded high-k film has. The decay rate of the relaxation current is in the order of nc-ZnO > nc-ITO > nc-Si > nc-Ru. When the relaxation currents of the nanocrystals embedded samples were fitted to the Curie-von Schweidler law, the n values were between 0.54 and 0.77, which are much lower than that of the non embedded high-k sample. The nanocrystals retain charges in two different states, i.e., deeply and loosely trapped. The ratio of these two types of charges was estimated. The charge storage capacity and holding strength are strongly influenced by the type of material of the embedded nanocrystals. The nc-ZnO embedded film holds trapped charges longer than other embedded films do. The ramp-relax result indicates that the breakdown of the embedded film came from the breakdown of the bulk high-k film. The type of nanocrystal material influences the breakdown strength.

Reliability of nc-ZnO Embedded ZrHfO High-kNonvolatile Memory Devices Stressed at High Temperatures

“…Yang et al [16,17] demonstrated that the nc-ZnO embedded ZrHfO sample had a larger breakdown voltage than the non-embedded ZrHfO sample. Yang et al [16,17] demonstrated that the nc-ZnO embedded ZrHfO sample had a larger breakdown voltage than the non-embedded ZrHfO sample.…”

“…Therefore, the nanocrystals embedded high-k structure can potentially replace the conventional poly-Si floating-gate structure in high-density NVMs [3][4][5]. Yang et al [16] also reported that the nc-ZnO embedded ZrHfO film had a large charge holding capability with strong breakdown strength. Recently, nanocrystalline (nc) metals, metal oxides or semiconductor materials, such as Ru, Ni, indium tin oxide (ITO), Si, and zinc oxide (ZnO), have been embedded into the high-k dielectric for nonvolatile memory applications.…”

“…The Zr-doped HfO 2 (ZrHfO) high-k film has many superior material and electrical properties than the undoped HfO 2 film in areas such as the high crystallization temperature, the large effective k value, and the low interface state density [6][7][8][9][10]. However, most reliability studies on nonvolatile memories were done at the room temperature [16][17]. They provide more choices on work functions, nanocrystal sizes, deposition methods, etc.…”

Stress-Induced Deterioration of Nanocrystalline ITO Embedded ZrHfO High-k Nonvolatile Memories

“…Recently, Yang et al (11) showed that nc-ITO embedded ZrHfO film also has the large charge holding capability and strong breakdown strength. However, there is lack of information on the reliability properties of this kind of device, such as the stress-induced deterioration process (11)(12)(13). In this work, authors investigated the stress-induced deterioration mechanism of the nc-ITO embedded ZrHfO MOS capacitor.…”

(Invited) Performance and Reliability of Nanocrystals Embedded High-k Nonvolatile Memories

“…Time dependent breakdown curves of the ZrHfO and the nc-ZnO embedded ZrHfO capacitors at various stress V g 's(15).…”