Improved reliability and switching performance of atom switch by using ternary Cu-alloy and RuTa electrodes

Tada, Munehiro; Sakamoto, Toshitsugu; Banno, Naoki; Okamoto, K.; Miyamura, Miharu; Iguchi, N.; Hada, H.

doi:10.1109/iedm.2012.6479133

Cited by 12 publications

(11 citation statements)

References 4 publications

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“…Conductive Bridging RAM (CBRAM) are envisaged as a promising candidate for future memory generations, due to their high speed, low voltage, low consumption and ease of integration in the back end of a logic process [1][2][3][4][5]. New CBRAM generations use an oxide as electrolyte and a Cubased active electrode in order to improve the thermal stability (i.e.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the physical mechanisms governing data-retention in down to 10nm nano-trench Al<inf>2</inf>O<inf>3</inf>/CuTeGe conductive bridge RAM (CBRAM)

Molas

Vianello

et al. 2013

2013 IEEE International Electron Devices Meeting

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In this work, we present an experimental and theoretical analysis of scaled (down to 10nm) Al 2 O 3 /CuTeGe based CBRAM. We focus on the understanding of the physical mechanisms responsible for the failure of high and low resistance states at high temperature. Using a numerical model combined with ab-initio calculations, we elucidate for the 1 st time at our knowledge the role of the filament morphology on the resistance instability. We demonstrate that an optimized filament shape (tuned by adjusting the operating conditions) significantly improves the memory window stability at high temperatures.

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Section: Introductionmentioning

confidence: 99%

Investigation of the physical mechanisms governing data-retention in down to 10nm nano-trench Al<inf>2</inf>O<inf>3</inf>/CuTeGe conductive bridge RAM (CBRAM)

Molas

Vianello

et al. 2013

2013 IEEE International Electron Devices Meeting

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“…A buffer prevents Cu oxidation and forms the Cu alloy at the surface of Cu electrode. It also stabilizes the ON-state by doping AlTi into the Cu bridge [8], [9]. The upper part of the buffer changes to metal oxides during the fabrication process.…”

Section: Methodsmentioning

confidence: 99%

“…4(c)]. The PSE and alloy electrodes [6]- [9] contribute to forming-free programming and superior ON-state stability. The local Cu interconnect of M5 and semiglobal Cu interconnects of M6 and M7 were formed on the devices using dual-damascene processing and a low-k dielectric (k = 2.8).…”

Section: Methodsmentioning

confidence: 99%

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Cu Atom Switch With Steep Time-to-ON-State Versus Switching Voltage Using Cu Ionization Control

Banno

Tada

Sakamoto

et al. 2015

IEEE Trans. Electron Devices

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To break the tradeoff relationship between fast and low-voltage programming of a Cu atom switch, the effect of the composition in the AlTi oxide buffer layer placed on a Cu electrode is investigated. To improve the voltage dependence of time-to-ON-state, namely, switching slope (SS), the Cu ionization rate is increased by changing the composition ratio of the AlTi oxide buffer. An Al 0.5 Ti 0.5 O y buffer leads to an extremely steep SS of 56 mV/decade by eliminating metallic Al residue on the Cu electrode. This buffer enables fast (10 ns) and lowvoltage (∼2 V) programming, as demonstrated in a 1-Mbit array. Cycle endurance (>10 3 cycles) with a high ON/ OFF resistance ratio (>10 4 ) was also confirmed. The steep SS technology is indispensable for conducting bridges used in a low-power nonvolatile field-programmable gate array.Index Terms-Atom switch, electrochemical reaction, fieldprogrammable gate array (FPGA), nonvolatile memory, polymer, reconfigurable logic, solid electrolyte.

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“…Upper two layer semi-global interconnects were formed by a trench first dual-damascene process and finally upper Al-pads were fabricated. Figure 3(b) shows the Cross sectional TEM image of the fabricated Cu atom switches integrated on the 65nm-node CMOS [7]. The atom switch is formed under the via.…”

Section: Introductionmentioning

confidence: 98%

(Invited) Opportunities and Challenges of Atom Switch for Low-Power Programmable Logic

Tada¹,

Sakamoto²,

Hada³

2013

ECS Trans.

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Opportunities and challenges of atom switch featuring Cu nanometer-scale conducting bridge in the solid-electrolyte are discussed with comparing the other emerging memories. Atom switch having the high on/off conductance ratio is suitable to directly replace the conventional CMOS switch element, realizing the low-power, nonvolatile programmable logic. Reliability challenges of the atom switch are also discussed in the view point of the stabilization of the on-and off-states. IntroductionWith the increasing requirement of tasks and functions in digital circuit, flexibility and energy-efficiency play important roles in addressing future low-power computing systems. A flexible hard wired-logic such as a field-programmable gate array (FPGA) becomes of great interest as an accelerator for the low-power systems since no redundant hardware, namely no instruction fetch mechanisms and cache, is advantageous to shift critical code from CPU to the accelerator and run those algorithms using multiple streaming processes. However, the FPGA with the large area suffers from large parasitic resistance and capacitance, limiting power/performance improvement.One solution for overcoming the issues of conventional FPGAs is a replacement of the CMOS switch element composed of SRAM and transmission gate (TMG) to a compact resistive-change switch [1]. Figure 1 shows the schematic image of the operation principle of atom switch. The solid-electrolyte is sandwiched between the active (Cu) anode and the inert cathode (Ru). When a positive voltage is applied to the Cu electrode, a nanometer-scale conducting Cu-bridge is formed and the switch is turned on. Cu + ions are supplied via electrolysis from the solid-electrolyte/Cu interface. A positive voltage applied to the inert electrode annihilates the Cu bridge and turns the switch off. Figure 2 (a) shows a tradeoff relationship between on/off ratio and endurance in emerging nonvolatile memories. Figure 2 (b) shows a concept of a crossbar switch integrated in BEOL [2, 3], where the atom switches are densely-packed and directly route signals flexibly. The replacement of the switch block reduces the chip area, lowering dynamic power consumption. The nonvolatility also decreases the static power since an efficient tuning of power-gating can be realized. For the switch application, atom switch having the high on/off conductance ratio is more suitable than the other memories. In the previous work, the 70 % dynamic power and 72 % area reductions were demonstrated in a 90 nm-node, test-vehicle [4]. In reality, once the FPGA is programmed, the configuration is not so much frequently re-programmed. Therefore, the >10 3 endurance of atom switch is acceptable for the programmable logic application so far.In this paper, an operation principle of the atom switch is reviewed and the application is discussed. For reliability challenge, a complementary atom switch (CAS) [5,6] and alloying electrode [7] are proposed. The pair of the switches works as one

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Improved reliability and switching performance of atom switch by using ternary Cu-alloy and RuTa electrodes

Cited by 12 publications

References 4 publications

Investigation of the physical mechanisms governing data-retention in down to 10nm nano-trench Al<inf>2</inf>O<inf>3</inf>/CuTeGe conductive bridge RAM (CBRAM)

Investigation of the physical mechanisms governing data-retention in down to 10nm nano-trench Al<inf>2</inf>O<inf>3</inf>/CuTeGe conductive bridge RAM (CBRAM)

Cu Atom Switch With Steep Time-to-ON-State Versus Switching Voltage Using Cu Ionization Control

(Invited) Opportunities and Challenges of Atom Switch for Low-Power Programmable Logic

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