Effects of O3 and H2O as oxygen sources on the atomic layer deposition of HfO2 gate dielectrics at different deposition temperatures

Lee, Sang Young; Kim, Hyo Kyeom; Lee, Jong Ho; Yu, Il-Hyuk; Lee, Jae-Ho; Hwang, Cheol Seong

doi:10.1039/c3tc32561j

Cited by 45 publications

(22 citation statements)

References 45 publications

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“…Although the HfO 2 thin‐film deposited at 200 °C shows the highest ionic conductivity, the XPS spectra in Figure 2c show a non‐negligible carbon peak near 288.8 eV, indicating carbon‐containing residue from incomplete ALD reactions which may contaminate the ECRAM device. [ 40 ] Therefore, deposition temperature of 250 °C was chosen for the best available ion conducting film. The effect of the measurement temperature on the ionic conductivity of the HfO 2 thin‐film deposited at 250 °C was further characterized to estimate the ionic conductivity of the film at room temperature (Figure 2e).…”

Section: Resultsmentioning

confidence: 99%

Elucidating Ionic Programming Dynamics of Metal‐Oxide Electrochemical Memory for Neuromorphic Computing

Jeong

Lee

Ryu

et al. 2021

Adv Elect Materials

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Cross‐point arrays of synaptic devices have been investigated as a core platform for neuromorphic computing architectures. To achieve a significant speed boost in deep neural network computations compared to the von Neumann architecture, it is essential to develop synaptic devices with optimal performance for fully parallel vector‐matrix‐multiplication. Among various non‐volatile memory candidates, metal‐oxide based electrochemical random‐access memory (ECRAM) is considered as a promising analog synapse due to its superior switching characteristics and CMOS‐compatibility. However, the switching mechanisms of metal‐oxide ECRAM remain to be understood, impeding improvements of the synaptic characteristics and device performance. Here, ionic programming dynamics based on oxygen ion migration and associated redox‐reactions are investigated in metal‐oxide ECRAMs by considering ion transport via the electrolyte and diffusion in the channel. Additionally, the origins of update asymmetry and long‐term retention found in voltage‐pulse programming measurements are explained by non‐uniform distribution of the off‐stoichiometry in the channel layer. By exploiting the programming mechanism, ECRAMs can achieve desirable synaptic characteristics under voltage‐pulse mode. Finally, experimental and simulation studies consistently suggest that channel and electrolyte with high ionic transport properties can improve the performance of metal‐oxide ECRAMs, opening a path toward optimized synaptic device characteristics for the maximum computation performance.

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Section: Resultsmentioning

confidence: 99%

Elucidating Ionic Programming Dynamics of Metal‐Oxide Electrochemical Memory for Neuromorphic Computing

Jeong

Lee

Ryu

et al. 2021

Adv Elect Materials

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“…The O 3 sample has higher capacitance values than the H 2 O sample. Although the O 3 precursor has a stronger oxidizing ability than H 2 O precursor, unwanted interfacial growth of SiO x on a silicon substrate is higher [58,59], but since there are fewer interface traps at the interface in the O 3 sample, it was judged that the capacitance value will be larger in O 3 sample. A correlation study of the growth rate, thickness uniformity, stoichiometry, and hydrogen impurity level was discussed in previous work [60].…”

Section: Resultsmentioning

confidence: 99%

Effects of Oxygen Precursor on Resistive Switching Properties of CMOS Compatible HfO2-Based RRAM

Ryu

Kim

2021

Metals

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In this work, we investigate the resistive switching behaviors of HfO2-based resistive random-access memory (RRAM) in two different oxidants (H2O and O3) in an atomic layer deposition system. Firstly, the surface characteristics of the Ni/HfO2/Si stack are conducted by atomic force microscopy (AFM). A similar thickness is confirmed by scanning electron microscope (SEM) imaging. The surface roughness of the HfO2 film by O3 (O3 sample) is smoother than in the sample by H2O (H2O sample). Next, we conduct electrical characteristics by current–voltage (I–V) and capacitor–voltage (C–V) curves in an initial process. The forming voltage of the H2O sample is smaller than that of the O3 sample because the H2O sample incorporates a lot of H+ in the film. Additionally, the smaller capacitor value of the H2O sample is obtained due to the higher interface trap in H2O sample. Finally, we compare the resistive switching behaviors of both samples by DC sweep. The H2O sample has more increased endurance, with a smaller on/off ratio than the O3 sample. Both have good non-volatile properties, which is verified by the retention test.

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“…announced that HfO2, a high-k inorganic material with an ultrahigh melting point (3085 K) [5], a sufficient electrical breakdown field (3.9-6.7 MV/cm) [6], low thermal conductivity (~2.55 W•K -1 •m -1 ), and four times the density (9.68 g/cm 3 ) of SiO2 (2.26 g/cm 3 ) [7], as the most promising dielectric layer material to replace the traditional SiO2 layer for a new generation of supercomputers [8]. for HfO2 films grown using different methods, such as metal-organic CVD (MOCVD) [9][10][11], thermal CVD (TCVD) [12], atomic layer deposition (ALD) [13][14][15][16][17], sol-gel [18][19][20], radio frequency magnetron sputtering (RFMS) [21] and pulsed laser deposition (PLD) [22]. As a result of the extremely low deposition rate of HfO2 films, only a few scholars have studied the growth of films with thicknesses below 100 nm over the last decade, such that HfO2 films have not been exploited at the micron scale.…”

Section: Introductionmentioning

confidence: 99%

High-Throughput Growth of HfO2 Films Using Temperature-gradient Laser Chemical Vapor Deposition

Liu

WANG

et al. 2021

Preprint

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The use of hafnia (HfO2) has facilitated recent advances in combining uprated dielectric layers (UDLs) and environmental barriers (EBs) in supercomputers. However, an extremely low deposition rate limits further development and fabrication efficiency of HfO2 films. In this study, high-throughput growth of HfO2 films was realized via laser chemical vapor deposition using a laser spot with a gradient temperature distribution. In HfO2 films fabricated by a single growth process, four regions with different morphologies could be discerned for deposition temperatures increasing from 1300 K to 1600 K: leaf-like, pyramid-like, bromeliad-like and pinecone-like. Two growth modes were observed for Regions I and II: Stranski-Krastanov and Volmer-Weber. Regions III and IV contained coexisting monoclinic and tetragonal HfO2 grains with an in-plane boundary for m-HfO2 (-110) {111}//t-HfO2 (1-11) {111}. The maximum deposition rate reached 362 μm/h, which was 102 - 104 times higher than that obtained using existing deposition methods.

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Effects of O₃ and H₂O as oxygen sources on the atomic layer deposition of HfO₂ gate dielectrics at different deposition temperatures

Abstract: Variations in the (a) growth rate and (b) film density, measured via the XRR of the HfO2 films with O3 and H2O oxidants as a function of Ts (160–360 °C).

Cited by 45 publications

References 45 publications

Elucidating Ionic Programming Dynamics of Metal‐Oxide Electrochemical Memory for Neuromorphic Computing

Elucidating Ionic Programming Dynamics of Metal‐Oxide Electrochemical Memory for Neuromorphic Computing

Effects of Oxygen Precursor on Resistive Switching Properties of CMOS Compatible HfO2-Based RRAM

High-Throughput Growth of HfO2 Films Using Temperature-gradient Laser Chemical Vapor Deposition

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