M. J. Tsai

Low-Power and Nanosecond Switching in Robust Hafnium Oxide Resistive Memory With a Thin Ti Cap

The memory performance of hafnium oxide (HfOx)-based resistive memory containing a thin reactive Ti buffer layer can be greatly improved. Due to the excellent ability of Ti to absorb oxygen atoms from the HfOx film after post-metal annealing, a large amount of oxygen vacancies are left in the HfOx layer of the TiN/Ti/HfOx/TiN stacked layer. These oxygen vacancies are crucial to make a memory device with a stable bipolar resistive switching behavior. Aside from the benefits of low operation power and large on/off ratio (>100), this memory also exhibits reliable switching endurance (>106 cycles), robust resistance states (200°C), high device yield (~100%), and fast switching speed (<10 ns).

Good Endurance and Memory Window for

A scaling feasibility for the process integration of the Ti/HfO_x, resistance memory with pillar structure is studied in this letter. An empirical model is successfully developed to correlate the forming voltage of devices to their cell sizes. The abnormal increase in the breakdown voltage and the absence of the resistance switching characteristic for the scaled devices (<; 150 nm) are observed for the devices encapsulated with the SiO₂ film. This result is attributed to the reduction in the oxy gen-gettering ability of the Ti top layer by the SiO₂ passivation layer. For scaled devices with the Si₃N₄ passivation layer, the Ti film retains the same oxygen-gettering ability as the large devices. A 0.5-V reduction in the forming voltage for the 50-nm devices by using the S₃N₄, instead of the SiO₂, layer is observed. The 50-nm devices with the Si₃N₄ encapsulating layer exhibits improved memory performances such as large on/off ratio (>; 100), high temperature stability at 200 °C for 500 min, and satisfactory endurance (10⁴ cycles).

\hbox{Ti/HfO}_{x}

Department of Electronic Engineering, Chang Gung University, Tao-Yuan, Taiwan, R.O.C. Electronics and Optoelectronics Research Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan, R. O. C. Department of Material Science Engineering, National Taiwan University, Taipei, Taiwan, R.O.C. Department of Electrical Engineering, National Central University, Chungli, Taiwan, R.O.C. Corresponding author: Tel: 886-3-5913913 Fax: 886-3-5917690 E-mail: sidhu@mail.cgu.edu.tw

Pillar RRAM at 50-nm Scale by Optimal Encapsulation Layer

The scalability issue of 1T-1R Ti/HfOx BRM, which is resulted from the interaction between BRM and transistor, is demonstrated. While a sufficiently lower Vforming can mitigate the RP, an alternative buffer layer Ta is also proposed to further scale the 1T-1R HfOx based BRM.

Very low voltage operation of p-Si/Al2O3/HfO2/TiO2/Al2O3/Pt single quantum well flash memory devices with good retention

Many kinds of nonvolatile memory (NVM) devices with the technical limitations of scalability potential, higher switching power, nonvolatility, and reliability, etc have been reported by several groups[1-3]. To overcome those problems, a resistive switching memory device is one of the promising candidates for future nanoscale memories in the semiconductor industry. Different binary oxide memory elements such as NiOx [4], HfOx [5], Cu2O [6], etc have been reported by several groups. It is also expected that the flash memory device can be replaced by resistive switching memory in future. Recently, the resistive switching memory of the electrochemical formation and removal of metallic pathways in the GeSe solid electrolytes have been reported [7]. Due to the GeSe process limitation, the high-κ solid electrolyte can be used for the nanoscale resistive switching memory applications. In this study, we have investigated the resistive switching memory in a Cu/Ta2O5/TiN/Si structure for the first time.

Scalability issue in Ti/HfO bipolar resistive memory with 1T-1R configuration by resistance pinning effect during 1 st RESET and its solution

Y. S. Chen, H. Y. Lee, P. S. Chen, P. Y. Gu, Y. Y. Hsu, W. H. Liu, C. H. Tsai, S. M. Wang, S. S. Sheu, P. C. Chiang, W. P. Lin, W. S. Chen, F. T. Chen, C. H. Lien, and M.-J. Tsai Electronics and Optoelectronics Research Laboratory, Industrial Technology Research Institute, Institute of Electronics Engineering, National Tsing Hua University, Department of Chemical and Materials Engineering, MingShin University of Science & Technology, Taiwan R.O.C., Phone: 886-3-5912958, Fax: 886-3-5917690, E-mail: yusheng@itri.org.tw

Resistive Switching Memory using High-κ Ta 2 O 5 Films

The HfOx device with CMOS compatible W BE is successfully demonstrated. The devices exhibit the low VFORM and good switching performance. The coexistence of bipolar and unipolar switching for the Ti/HfOx/W device is presented. The current reduction of bipolar and unipolar operation is by the decrease of compliance current and cell size, respectively.

Overview and Future Challenges of Hafnium Oxide ReRAM

Promising resistive switching memory characteristics in a IrO_x/GdO_x/W structure have been investigated. The surface roughness of bottom electrode plays a major role for forming-free and low current resistive switching, due to electric field enhancement. Memory device shows repeatable switching cycles with a small compliance current of 20 μA (60μW), long program/erase endurance of >10⁴ cycles, and excellent data retention of >10⁴ s at 85°C.

Good memory performance and coexistence of bipolar and unipolar resistive switching for CMOS compatible Ti/HfO x /W memory

Improved resistive switching memory characteristics in a novel W/TaO_x/TiO_xN/TiN device with a small current compliance of 50 μA have been investigated. Memory device has shown consecutive repeatable resistive switching cycles (>10²) with small operation voltage of ±1.5V. The device with TaO_x/TiO_xN shows improved resistance ratio of ~40 as compared to TiO_xN device (~7). The switching mechanism is attributed to the formation/dissolution of O_xygen vacancy filament. The memory device has shown good read endurance of >7.5×10⁵ cycles and excellent data retention of >5 hours at 85°C.

Rough surface improved formation-free low power resistive switching memory using IrO x /GdO x /W structure

1T-1R Zr/HfO_x RRAM with improved uniformity is proposed, which is due to the easily O_xidation of Zr layer from both HfO_x and supporting SiO₂. The formation of ZrO_x become a good current limiter which help the device prevent scalability issue.