Structural dependence of dielectric breakdown in ultra-thin gate oxides and its relationship to soft breakdown modes and device failure

Wu, Ernest Y.; Nowak, E.; Aitken, J.; Abadeer, W.; Han, Lei; Lo, Shih-Shou

doi:10.1109/iedm.1998.746316

Cited by 79 publications

(43 citation statements)

References 3 publications

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“…Weir et al [99] concluded that there was no significant degradation observed in the transistor parameters and following soft breakdown and indicated that perhaps only analog circuitry would be affected by an increased gate current noise. Similar findings were reported on the effect of soft breakdown on transistor performance if the breakdown spot was not located in the device's source or drain region [103], [106], [107]. It was shown in [106] that hard breakdown and catastrophic device failure occurred more frequently as the channel length of the device was decreased.…”

Section: ) Device-level Failuresupporting

confidence: 80%

Ultrathin gate oxide reliability: physical models, statistics, and characterization

Suehle

2002

IEEE Trans. Electron Devices

144

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Abstract-The present understanding of wear-out and breakdown in ultrathin ( 5 0 nm) SiO 2 gate dielectric films and issues relating to reliability projection are reviewed in this article. Recent evidence supporting a voltage-driven model for defect generation and breakdown, where energetic tunneling electrons induce defect generation and breakdown will be discussed. The concept of a critical number of defects required to cause breakdown and percolation theory will be used to describe the observed statistical failure distributions for ultrathin gate dielectric breakdown. Recent observations of a voltage dependent voltage acceleration parameter and non-Arrhenius temperature dependence will be presented. The current understanding of soft breakdown will be discussed and proposed techniques for detecting breakdown presented. Finally, the implications of soft breakdown on circuit functionality and the applicability of applying current reliability characterization and analysis techniques to project the reliability of future alternative gate dielectrics will be discussed.

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Section: ) Device-level Failuresupporting

confidence: 80%

Ultrathin gate oxide reliability: physical models, statistics, and characterization

Suehle

2002

IEEE Trans. Electron Devices

144

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“…The obtained results, shown in Fig. 2, clearly indicate that the SBD probability increases with decreasing stress voltage and device area, in agreement with the results reported in [11].…”

Section: Resultssupporting

confidence: 81%

“…OFT BREAKDOWN (SBD) has been extensively studied in recent years because of its implications on the reliability of thin silicon dioxide films [1]- [11]. Such phenomenon is characterized by a large increase of the low field current and of the noise at the gate electrode.…”

mentioning

confidence: 99%

Characterization of soft breakdown in thin oxide NMOSFETs based on the analysis of the substrate current

Crupi

Iannaccone

Crupi

et al. 2001

IEEE Trans. Electron Devices

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We have investigated the properties of soft breakdown (SBD) in thin oxide (4.5 nm) nMOSFETs with measurements of the gate and substrate leakage currents using the carrier separation technique. We have observed that, at lower gate voltages, the level of the substrate current exhibits a plateau. We propose that the observed plateau is due to the Shockley-Hall-Read (SHR) generation of hole-electron pairs in the space charge region and at the Si-SiO2 interface. At higher voltages, the substrate current steeply increases with voltage, due to a tunneling mechanism, trap-assisted or due to a localized effective thinning of the oxide, from the substrate valence band to the gate conduction band, which becomes possible for gate voltages higher than the threshold voltage. The proposed interpretation is consistent with the results of measurements performed at different operating conditions, in the presence of light and in the case of substrate reverse bias. The presented results are also useful for characterizing the performance of MOSFETs after SBD

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“…This view was not consistent with a later statistical analysis of data [176] showing that the distribution of breakdown times is independent of whether they are soft or hard, and that an HBD which occurs after an SBD is a random event uncorrelated with the first SBD spot. It was also shown that SBD and HBD follow similar area dependence [177] but the temperature dependence and voltage dependence were found to be different [178] or the same [179] in different laboratories. The similar light emission spectral characteristics of SBD and HBD [180] also support the idea that they are related phenomena, differing only in the size of the breakdown spot.…”

Section: A Soft Breakdownmentioning

confidence: 95%

“…This will be referred to as "device breakdown." In a study of the channel length-and width-dependence of device breakdown in n-FETs stressed at 4.1 V, Wu [135], [177] showed that, for short-channel devices (0.2-m channel length), the distribution of oxide breakdown times for the first breakdown event coincides with the distribution of device breakdown times, whereas for longer channels (10 m) the device breakdown occurs some time after the first soft breakdown. After a "hard" breakdown, the device is clearly nonfunctional by any ordinary criterion, exhibiting a negative drain current when the gate-to-drain leakage exceeds the normal transistor on current [194].…”

Section: B Device Breakdownmentioning

confidence: 99%

Physical and predictive models of ultrathin oxide reliability in CMOS devices and circuits

Stathis

2001

IEEE Trans. Device Mater. Relib.

163

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Abstract-The microelectronics industry owes its considerable success largely to the existence of the thermal oxide of silicon. However, recently there is concern that the reliability of ultra-thin dielectrics will limit further scaling to slightly thinner than 2 nm. This paper will review the physics and statistics of dielectric wearout and breakdown in ultrathin SiO 2 -based gate dielectrics. Electrons or holes tunneling through the gate oxide generate defects until a critical density is reached and the oxide breaks down. The critical defect density is explained by the formation of a percolation path of defects across the oxide. Only 1% of these paths ultimately lead to destructive breakdown, and the microscopic nature of these defects is not known. The rate of defect generation decreases approximately exponentially with supply voltage, below a threshold voltage of about 5 V for hot electron-induced hydrogen release. However, the tunnel current also increases exponentially with decreasing oxide thickness, leading to a decreasing time-to-breakdown and a diminishing margin for reliability as device dimensions are scaled. Estimating the reliability of the dielectric requires an extrapolation from the measurement conditions (e.g., higher voltage) to operation conditions. Because of the diminished reliability margin, it has become imperative to try to reduce the error in this extrapolation.Long-term ( 1 year) stress experiments are now being used to measure the wearout and breakdown of ultrathin ( 2 nm) dielectric films as close as possible to operating conditions. These measurements have revealed the details of the voltage dependence of the defect generation rate and critical defect density, allowing better modeling of the voltage dependence of the time-to-breakdown. Such measurements are used to guide the technology development prior to the manufacturing stage. We then discuss the nature of the electrical conduction through a breakdown spot and the effect of the oxide breakdown on device and circuit performance. In some cases, an oxide breakdown does not lead to immediate circuit failure, so more research is needed in order to develop a quantitative methodology for predicting the reliability of circuits.

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Structural dependence of dielectric breakdown in ultra-thin gate oxides and its relationship to soft breakdown modes and device failure

Cited by 79 publications

References 3 publications

Ultrathin gate oxide reliability: physical models, statistics, and characterization

Ultrathin gate oxide reliability: physical models, statistics, and characterization

Characterization of soft breakdown in thin oxide NMOSFETs based on the analysis of the substrate current

Physical and predictive models of ultrathin oxide reliability in CMOS devices and circuits

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