Thickness independent reduced forming voltage in oxygen engineered HfO<sub>2</sub> based resistive switching memories

Sharath, Sankaramangalam Ulhas; Kurian, J.; Komissinskiy, Philipp; Hildebrandt, Erwin; Bertaud, T.; Walczyk, Christian; Calka, P.; Schroeder, Thomas; Alff, Lambert

doi:10.1063/1.4893605

Cited by 62 publications

(42 citation statements)

References 27 publications

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“…Particularly, the batch ALD technique with reduced cost per wafer has been developed for future mass production of related devices9. Despite of a bunch of detailed studies focusing on unveiling the RS mechanism (normally on μm-size devices1011) and on attempting to improve the cell-performances (with different methods like doping12131415, filament confinement1617 and bilayers18192021 etc. ), a fundamental but indispensable study correlating the material properties (e.g.…”

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confidence: 99%

Material insights of HfO2-based integrated 1-transistor-1-resistor resistive random access memory devices processed by batch atomic layer deposition

Niu

Kim

Roelofs

et al. 2016

Sci Rep

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With the continuous scaling of resistive random access memory (RRAM) devices, in-depth understanding of the physical mechanism and the material issues, particularly by directly studying integrated cells, become more and more important to further improve the device performances. In this work, HfO2-based integrated 1-transistor-1-resistor (1T1R) RRAM devices were processed in a standard 0.25 μm complementary-metal-oxide-semiconductor (CMOS) process line, using a batch atomic layer deposition (ALD) tool, which is particularly designed for mass production. We demonstrate a systematic study on TiN/Ti/HfO2/TiN/Si RRAM devices to correlate key material factors (nano-crystallites and carbon impurities) with the filament type resistive switching (RS) behaviours. The augmentation of the nano-crystallites density in the film increases the forming voltage of devices and its variation. Carbon residues in HfO2 films turn out to be an even more significant factor strongly impacting the RS behaviour. A relatively higher deposition temperature of 300 °C dramatically reduces the residual carbon concentration, thus leading to enhanced RS performances of devices, including lower power consumption, better endurance and higher reliability. Such thorough understanding on physical mechanism of RS and the correlation between material and device performances will facilitate the realization of high density and reliable embedded RRAM devices with low power consumption.

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confidence: 99%

Material insights of HfO2-based integrated 1-transistor-1-resistor resistive random access memory devices processed by batch atomic layer deposition

Niu

Kim

Roelofs

et al. 2016

Sci Rep

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“…Optimal learning rate constant η was found to be equal to 2 for used initial weights uniformly distributed on the interval. 2,8 The possible position of separating lines (in bold red), implemented by the hidden neurons, and the calculated output signal (heat map) are shown in Fig. 4a.…”

Section: Analogue Task Solvingmentioning

confidence: 99%

“…Memristive properties were found in inorganic (such as TiO x , HfO x , SiO x , etc. ), [7][8][9][10] organic (polyaniline, polyimide) 11,12 and hybrid organic/inorganic 13 materials. Organic or polymeric materials have unique advantages over traditional inorganic memristive devices, including high flexibility for biocompatible neuromorphic circuits and implants, low cost, solution processability, large-area implementation.…”

Section: Introductionmentioning

confidence: 99%

First steps towards the realization of a double layer perceptron based on organic memristive devices

et al. 2016

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Memristors are widely considered as promising elements for the efficient implementation of synaptic weights in artificial neural networks (ANNs) since they are resistors that keep memory of their previous conductive state. Whereas demonstrations of simple neural networks (e.g., a single-layer perceptron) based on memristors already exist, the implementation of more complicated networks is more challenging and has yet to be reported. In this study, we demonstrate linearly nonseparable combinational logic classification (XOR logic task) using a network implemented with CMOS-based neurons and organic memrisitive devices that constitutes the first step toward the realization of a double layer perceptron. We also show numerically the ability of such network to solve a principally analogue task which cannot be realized by digital devices. The obtained results prove the possibility to create a multilayer ANN based on memristive devices that paves the way for designing a more complex network such as the double layer perceptron.

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“…One origin of this layer is the extremely oxygen deficient layer itself as shown previously by XPS and hard X-ray photoelectron spectroscopy. 9,10 In this case, the conductivity arises from overlapping oxygen defect states. 7 The second origin is the formation of HfCx, i.e.…”

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confidence: 99%

“…7,8 RRAM devices based on these films show forming free resistive switching and the forming voltage is independent on the thickness of the highly oxygen deficient HfO2-x layer. 9,10 In this paper we discuss the reaction of carbon impurities to hafnium carbide and its influence on hafnium oxide-based resistive switching. The role of carbon impurities is of extremely high importance, as they are inherent to most of today's deposition techniques commonly used for fabricating complementary metal oxide semiconductor (CMOS) devices, such as atomic layer deposition (ALD) based on organic precursors.…”

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confidence: 99%

Hafnium carbide formation in oxygen deficient hafnium oxide thin films

Rodenbücher

Hildebrandt

Szot

et al. 2016

Applied Physics Letters

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On highly oxygen deficient thin films of hafnium oxide (hafnia, HfO2-x) contaminated with adsorbates of carbon oxides the formation of hafnium carbide (HfCx) at the surface during vacuum annealing at temperatures as low as 600 °C is reported. Using X-ray photoelectron spectroscopy the evolution of the HfCx surface layer related to a transformation from insulating into metallic state is monitored in situ. In contrast, for fully stoichiometric HfO2 thin films prepared and measured under identical conditions, the formation of HfCx was not detectable suggesting that the enhanced adsorption of carbon oxides on oxygen deficient films provides a carbon source for the carbide formation. This shows that a high concentration of oxygen vacancies in carbon contaminated hafnia lowers considerably the formation energy of hafnium carbide. Thus the presence of a sufficient amount of residual carbon in resistive random access memory devices might lead to a similar carbide formation within the conducting filaments due to Joule heating. HfO2 (hafnia) has been studied extensively in the last decades as a high- dielectric being used as replacement of the standard gate dielectric SiO2 in order to produce high-density logic and memory devices.1 Furthermore, it was found that HfO2 can undergo a local insulator-metal (IM) transition under the influence of an electric field opening up the possibility to use it as resistive switching material in redox-based random access memories (RRAM). 2,3During resistive switching in HfO2, a local redox reaction associated with a formation or modification of conducting filaments takes place, in which the movement of oxygen vacancies plays the key role for the modulation of the electric properties. [4][5][6] Hence, the investigation of the behavior of oxygen vacancies is important for RRAM device performance.In contrast to the local insulator-metal transition as observed in conducting filaments in HfO2 on the nanoscale, also a global insulator-metal transition on a macroscopic scale has been found in oxygen deficient hafnium oxide thin films grown by molecular beam epitaxy (MBE). 7,8 The oxygen deficiency in these films is created during growth under oxygen deficient conditions leading to a homogeneous distribution of oxygen vacancies. With increasing amount of oxygen vacancies, the band gap is consistently reduced and defect states inside the gap eventually form a defect band at the Fermi level.7,8 RRAM devices based on these films show forming free resistive switching and the forming voltage is independent on the thickness of the highly oxygen deficient HfO2-x layer. 9,10 In this paper we discuss the reaction of carbon impurities to hafnium carbide and its influence on hafnium oxide-based resistive switching. The role of carbon impurities is of extremely high importance, as they are inherent to most of today's deposition techniques commonly used for fabricating complementary metal oxide semiconductor (CMOS) devices, such as atomic layer deposition (ALD) based on organic precursors. Based on an in-ope...

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Thickness independent reduced forming voltage in oxygen engineered HfO₂ based resistive switching memories

Cited by 62 publications

References 27 publications

Material insights of HfO2-based integrated 1-transistor-1-resistor resistive random access memory devices processed by batch atomic layer deposition

Material insights of HfO2-based integrated 1-transistor-1-resistor resistive random access memory devices processed by batch atomic layer deposition

First steps towards the realization of a double layer perceptron based on organic memristive devices

Hafnium carbide formation in oxygen deficient hafnium oxide thin films

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Thickness independent reduced forming voltage in oxygen engineered HfO2 based resistive switching memories

Cited by 62 publications

References 27 publications

Material insights of HfO2-based integrated 1-transistor-1-resistor resistive random access memory devices processed by batch atomic layer deposition

Material insights of HfO2-based integrated 1-transistor-1-resistor resistive random access memory devices processed by batch atomic layer deposition

First steps towards the realization of a double layer perceptron based on organic memristive devices

Hafnium carbide formation in oxygen deficient hafnium oxide thin films

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Thickness independent reduced forming voltage in oxygen engineered HfO₂ based resistive switching memories