Shenghu Tan

Microscopic origin of read current noise in TaOx-based resistive switching memory by ultra-low temperature measurement

TaOx-based resistive random access memory (RRAM) attracts considerable attention for the development of next generation nonvolatile memories. However, read current noise in RRAM is one of the critical concerns for storage application, and its microscopic origin is still under debate. In this work, the read current noise in TaOx-based RRAM was studied thoroughly. Based on a noise power spectral density analysis at room temperature and at ultra-low temperature of 25 K, discrete random telegraph noise (RTN) and continuous average current fluctuation (ACF) are identified and decoupled from the total read current noise in TaOx RRAM devices. A statistical comparison of noise amplitude further reveals that ACF depends strongly on the temperature, whereas RTN is independent of the temperature. Measurement results combined with conduction mechanism analysis show that RTN in TaOx RRAM devices arises from electron trapping/detrapping process in the hopping conduction, and ACF is originated from the thermal activatio...

Resistive-Gate Field-Effect Transistor: A Novel Steep-Slope Device Based on a Metal—Insulator—Metal—Oxide Gate Stack

A novel silicon-based resistive-gate field-effect transistor (ReFET) with metal-insulator-metal-oxide gate stack is proposed. With the abrupt resistance change event from high-resistance state to low-resistance state in the introduced insulator layer, the threshold voltage of ReFET can be suddenly decreased, resulting in an abrupt switching of drain current. The device is capable of sub-60-mV/decade subthreshold slope (SS), as well as MOSFET-comparable ON-current. The fabricated n-type ReFET device with Pt/TiN/TaOx/Poly-Si/SiO2 gate stack can achieve steep SS of 8 mV/decade. With future materials and threshold voltage optimization, high ION/IOFF ratio with reduced operation voltage can be expected, which shows that ReFET is a promising candidate for ultralow power applications.

Material engineering technique for SiO X -based embedded RRAM with CMOS compatible process

The resistive switching behavior recently observed in silicon oxide (SiOX) makes this material attractive to embedded resistive random access memory (RRAM) fabrication due to process compatibility. In SiOX-based RRAM devices, switching mechanism is closely correlated with defects in the oxides. Therefore developing a method to control the defects is necessary for performance enhancement. In this paper, a new material engineering technique for SiOX-based embedded RRAM fabrication is proposed and experimentally demonstrated. Metal-Insulator-Metal (MIM) Al/SiO2/TiN capacitor can be converted into RRAM device with nitrogen ion implantation, which is fully compatible with CMOS process. The doped MIM device exhibits stable bipolar resistive switching behavior with large OFF/ON ratio. Compared with PECVD SiOXNY resistive switching device, this material engineering technique with better control of defects density is shown to improve the low resistance uniformity of the fabricated device.

Thermal impact on the resistance switching properties in tantalum oxide based RRAM

In this paper, the switching layer thickness and temperature impacts on resistance switching polarity of tantalum oxide (TaO_x) based resistive random access memory (RRAM) have been investigated. Our results show that at room temperature unipolar behavior was activated in thick TaO_x but failed in thin TaO_x, while in 280 °C condition thin TaO_x layer RRAM can also show stable unipolar characteristics. For thick TaO_x device, the unipolar behavior is attributed to more heat accumulation in thicker switching layer. In 280 °C condition, stable unipolar characteristic of thin TaO_x device is due to extra ambient heat offered. In addition, thin TaO_x RRAM with SiO₂ buffer layer is also fabricated to investigate the heat accumulation impact on operation polarity of RRAM devices. These results are helpful in obtaining the insight on understanding the switching mechanism of TaO_x RRAM and improve the RRAM device performance and reliability capability.