Stressing and high field transport studies on device-grade SiO2 by ballistic electron emission spectroscopy

Ludeke, R.; Wen, Huimin; Cartier, E.

doi:10.1116/1.588845

Cited by 35 publications

(23 citation statements)

References 20 publications

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“…This high voltage low current imaging was done at the expense of lateral resolution, but was necessary to generate repeatable scans. Similar setpoint voltages with nanoamp currents have been used by others in STM experiments with thinner oxides, 25,29 as well as BASTM, 27 and BEEM 10,12,28 experiments. Initially the chips were scanned over 10 m to image the patterned circles to verify that our scan parameters were producing a reliable image.…”

Section: Resultsmentioning

confidence: 99%

“…However ultrathin (Ͻ3.5 nm͒ layers of silicon dioxide, such as those used in the TSD, allow sufficient tunneling current to make STM a viable tool for examining local conductivity. Others have been able to study ultrathin oxides in experiments with beam assisted scanning tunneling microscopy ͑BASTM͒, 27 with BEEM, 10,12,28 and with STM of thinner oxides. 25,29 We have found that by operating at high tip voltages ͑1-5 V͒ and lower than usual tunneling currents ͑1-5 pA͒, the tip may be rastered over the silicon dioxide surface, yielding an image without crashing.…”

Section: A Introductionmentioning

confidence: 99%

“…Studies of current-voltage (I-V) and capacitance voltage (C-V) characteristics, [1][2][3][4][5][6][7] as well as more basic surface studies using x-ray photoemission spectroscopy ͑XPS͒ 4,8,9 and ballistic electron emission microscopy ͑BEEM͒, [10][11][12] have greatly enhanced our understanding of current transport through these oxides, the chemical nature of the Si-SiO 2 interface, and the effects of electrical stressing. However, as the bulk of this work has been aimed at studying the future of the MOSFET, few studies have attempted to stress thin oxides (Ͻ3.5 nm͒ with very high current densities (Ͼ4ϫ10 3 A/cm 2 ).…”

Section: Introductionmentioning

confidence: 99%

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Macroscopic and microscopic studies of electrical properties of very thin silicon dioxide subject to electrical stress

Daniel

Jones

Marsh

et al. 1997

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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The electrical characteristics of various size tunnel switch diode devices, composed of Al/SiO 2 /n-Si/p ϩ -Si layers, which operate with a range of parameters ͑such as current densities in excess of 10 4 A/cm 2 ) that stress the oxide layer far beyond the levels used in typical thin oxide metal-oxide semiconductor research have been examined. It is found that the first time a large current and electric field are applied to the device, a ''forming'' process enhances transport through the oxide in the vicinity of the edges of the gate electrode, but the oxide still retains its integrity as a tunnel barrier. The device operation is relatively stable to stresses of greater than 10 7 C/cm 2 areally averaged, time-integrated charge injection. Duplication and characterization of these modified oxide tunneling properties was attempted using scanning tunneling microscopy ͑STM͒ to stress and probe the oxide. Electrical stressing with the STM tip creates regions of reduced conductivity, possibly resulting from trapped charge in the oxide. Lateral variations in the conductivity of the unstressed oxide over regions roughly 20-50 nm across were also found.

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Section: Resultsmentioning

confidence: 99%

Section: A Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Macroscopic and microscopic studies of electrical properties of very thin silicon dioxide subject to electrical stress

Daniel

Jones

Marsh

et al. 1997

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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“…7 As a main result, it was found that the breakdown of state-of-the-art gate oxides is still controlled by defects and impurities in the oxide and far away from the theoretical limit.…”

Section: ͓S0163-1829͑99͒06704-1͔mentioning

confidence: 98%

Temperature-dependent studies of InAs base layers for ballistic electron emission microscopy

et al. 1999

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InAs is a promising base material for ballistic electron emission microscopy ͑BEEM͒, since in this material the attenuation length of ballistic electrons is more than one order of magnitude larger than for metal base layers and the corresponding transmission factor for ballistic electrons is strongly enhanced. In this work, temperature-dependent BEEM studies on InAs base layers grown on GaAs substrates are performed. Unlike on samples with metal base layers, it is found that the transmission coefficient of the InAs base decreases with decreasing temperature. In addition, a strongly increasing conduction band offset at the InAs-GaAs interface with decreasing temperature is also observed. ͓S0163-1829͑99͒06704-1͔During the last years, ballistic electron emission microscopy 1,2 ͑BEEM͒ turned out to be a useful tool for local studies of semiconductor interfaces and subsurface sample properties. In a typical BEEM experiment, the scanning tunnel microscope ͑STM͒ tip is used to inject electrons into a thin metal film which is evaporated on a semiconductor sample. Some of these electrons will cross the metal ͑base͒ layer ballistically, and if their energy is high enough, they overcome the Schottky barrier at the metal-semiconductor interface. Subsequently, those electrons penetrate into the semiconductor and relax to the conduction band edge. The corresponding current is measured via a backside collector contact. The measured ballistic electron current as a function of sample bias is called the BEEM spectrum. In the BEEM spectrum, the onset bias of the BEEM current is only determined by the Schottky barrier height and the local resolution of these measurements can be as good as 1 nm. In this way, e.g., local inhomogeneities in the Schottky barrier on Au-Si ͑111͒ interfaces 3 were resolved.Originally, BEEM was applied to determine fundamental semiconductor properties such as metal-semiconductor barrier heights, band structure, or hot electron transport effects. 4,5 Recently, some attempts have been made to extend BEEM towards characterization of device structures. In detail, BEEM was used to study gate oxides in silicon metaloxide-semiconductor field effect transistors ͑MOSFET's͒.Here mainly two effects were studied: charge trapping 6 in the SiO 2 and stressing behavior. 7 As a main result, it was found that the breakdown of state-of-the-art gate oxides is still controlled by defects and impurities in the oxide and far away from the theoretical limit.Not only surface, but also subsurface sample properties can be investigated by BEEM. On a GaAs/AlGaAs doublebarrier structure, it was possible to investigate the resonant states, 8 and on a GaAs-AlGaAs superlattice, ballistic transport through minibands was studied. 9 Utilizing its outstanding spatial resolution, BEEM was also used to investigate self-assembled InAs quantum dots. 10,11 The BEEM current was found to be enhanced on the dots, and the fine structure in the BEEM spectrum measured on a single dot was attributed to the quantized states inside the dot. Motivated by th...

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“…Such extreme low values are attributed to leakage of the trapped charge, a process believed to occur in the prebreakdown region. 28 The data presented in Fig. 3 correspond to the highest value measured at several stressing places for a given electron kinetic energy.…”

Section: A Observation Of Existing Traps and Mechanisms Of New Trap mentioning

confidence: 98%

Investigation of existing defects and defect generation in device-grade SiO2 by ballistic electron emission spectroscopy

Wen¹

1997

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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Degradation processes initiated by defect generation in device-grade SiO2 were studied by locally injecting hot electrons from a scanning tunneling microscope tip into Pd/SiO2/p-Si(100) metal–oxide semiconductor (MOS) structures. An analysis of the emerging collector current in the Si substrate, a technique known as ballistic electron emission microscopy, provides electron transport information, from which the oxide defect generation process was studied. The charging of the defects resulted in shifts of threshold energies for electron transport across the oxide. A novel sheet charge model was developed to assess the in-depth distribution and charge densities in the oxide from field-induced threshold shifts obtained from experiment. An as-fabricated MOS system with an oxide thickness of 71 Å was investigated and found to contain existing electron traps of charge densities in the range (0.7–2.8)×1013 e/cm2 that are distributed within a 30 Å region adjacent to the metal/oxide interface. Further stressing was performed at zero oxide bias with increasing tip voltages of up to −10 V. New electron traps characterized by charge densities of (1.9–3.6)×1013 e/cm2 and located within 40 Å of the SiO2/Si interface were generated when the kinetic energy of the electrons injected into the SiO2 conduction band exceeded 1.9 eV. This energy threshold is in very good agreement with the hydrogen-release energy that is frequently invoked to explain oxide degradation.

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Stressing and high field transport studies on device-grade SiO2 by ballistic electron emission spectroscopy

Cited by 35 publications

References 20 publications

Macroscopic and microscopic studies of electrical properties of very thin silicon dioxide subject to electrical stress

Macroscopic and microscopic studies of electrical properties of very thin silicon dioxide subject to electrical stress

Temperature-dependent studies of InAs base layers for ballistic electron emission microscopy

Investigation of existing defects and defect generation in device-grade SiO2 by ballistic electron emission spectroscopy

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