Characterization of local dielectric breakdown in ultrathin SiO2 films using scanning tunneling microscopy and spectroscopy

Watanabe, Heiji; Baba, Takanobu; Ichikawa, Masakazu

doi:10.1063/1.370182

Cited by 40 publications

(24 citation statements)

References 27 publications

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“…19 Each point represents data averaged from more than 5 measurements of the same flake. The EBD obtained in this study is in agreement with that reported previously for thin BN.…”

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confidence: 99%

Layer-by-Layer Dielectric Breakdown of Hexagonal Boron Nitride

Hattori

Taniguchi²,

Watanabe³

et al. 2014

ACS Nano

200

218

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Hexagonal boron nitride (BN) is widely used as a substrate and gate insulator for two-dimensional (2D) electronic devices. The studies on insulating properties and electrical reliability of BN itself, however, are quite limited. Here, we report a systematic investigation of the dielectric breakdown characteristics of BN using conductive atomic force microscopy. The electric field strength was found to be ~12 MV/cm, which is comparable to that of conventional SiO2 oxides because of the covalent bonding nature of BN. After the hard dielectric breakdown, the BN fractured like a flower into equilateral triangle fragments. However, when the applied voltage was terminated precisely in the middle of the dielectric breakdown, the formation of a hole that did not penetrate to the bottom metal electrode was clearly observed. Subsequent I-V measurements of the hole indicated that the BN layer remaining in the hole was still electrically inactive. Based on these observations, layer-by-layer breakdown was confirmed for BN with regard to both physical fracture and electrical breakdown. Moreover, statistical analysis of the breakdown voltages using a Weibull plot suggested the anisotropic formation of defects. These results are unique to layered materials and unlike the behavior observed for conventional 3D amorphous oxides.

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“…19 Each point represents data averaged from more than 5 measurements of the same flake. The EBD obtained in this study is in agreement with that reported previously for thin BN.…”

mentioning

confidence: 99%

Layer-by-Layer Dielectric Breakdown of Hexagonal Boron Nitride

Hattori

Taniguchi²,

Watanabe³

et al. 2014

ACS Nano

200

218

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“…5 Recently, the use of scanned probes to perform local electrical measurements on thin SiO 2 films has provided an opportunity for studying the underlying breakdown mechanisms, which operate at the nanoscale. 6 Conductive-atomic force microscopy ͑CAFM͒ has been employed to examine local variations in Fowler-Nordheim tunneling due to variations in oxide thickness. 7 Scanning tunneling microscopy has been used to generate, and subsequently image, isolated stress induced quasibreakdown sites, 6 and CAFM employed further to observe local current fluctuations attributed to charging of stress-induced defect sites.…”

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confidence: 99%

“…6 Conductive-atomic force microscopy ͑CAFM͒ has been employed to examine local variations in Fowler-Nordheim tunneling due to variations in oxide thickness. 7 Scanning tunneling microscopy has been used to generate, and subsequently image, isolated stress induced quasibreakdown sites, 6 and CAFM employed further to observe local current fluctuations attributed to charging of stress-induced defect sites. 8 In this letter we make use of CAFM to study the nanoscale spatial distribution of quasibreakdown in native SiO 2 films.…”

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confidence: 99%

“…Figure 1 shows a typical current image, obtained for a constant sample bias of 1.0 V. Several sites can be identified by an enhanced local conductivity, each extending over an area of order 100 nm 2 , which is the estimated quasibreakdown area. 6 The electrical conductivity of the film is dominated by quasibreakdown through such localized leakage paths ͑dark areas in Fig. 1 represent a current up to 10 nA͒; in other regions of the film the current remains low ͑light areas in Fig.…”

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confidence: 99%

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Nanoscale electrical characterization of trap-assisted quasibreakdown fluctuations in SiO2

Pakes

Ramelow

Prawer

et al. 2004

Applied Physics Letters

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Conductive atomic force microscopy has been used to electrically image quasibreakdown sites in thin, native SiO2 films. Local current–voltage spectroscopy reveals, at individual sites, fluctuations in the breakdown current between well-defined conductivity states. Theoretical modeling has been performed to show that conduction through the film is governed by local trap-assisted tunneling, with typically one or two charge traps contributing to conduction through a quasibreakdown site. Our study provides a semiquantitative analysis to characterize the effective trap states that give rise to local random telegraph signals in the oxide film.

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“…Watanabe et al 16 have investigated the local dielectric breakdown of ultrathin SiO 2 films by STM/STS and observed quasibreakdown spots on the surface as a result of the change of conductance due to the hot electron injection at high bias voltage of 10 V. Although in our case a considerably smaller bias voltage of 100 mV was applied to the sample during topography imaging, a local breakdown might still occur due to the stronger electric field that may exist at the top of the nanocolumn. However, an electrical breakdown should lead to observable surface topographical change, which was not detected in our scans.…”

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confidence: 99%