Optical Properties of Tantalum Oxide Films on Silicon

Revesz, A. G.; Reynolds, J. H.; Allison, J.

doi:10.1149/1.2132963

Cited by 22 publications

(18 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Using the definition in Eq. ͑1͒ and the published data, the range of band gap values reduces from 4.1 ͑thermal oxidation of Ta or e-beam evaporation of Ta 2 O 5 ), 13 4.2 ͑polycrystalline CVD͒, 12 4.4 ͑anodized Ta͒, 5 15 Since we only looked at the OCPV in films with a TiN bottom electrode, the swing in the flat band condition with top electrode metal does not establish whether or not the bottom electrode is pinned at the defect level. We will discuss this further in Sec.…”

Section: General Optical Propertiesmentioning

confidence: 69%

“…This is to be contrasted with the wide range of optical band gap values ͑3.9-5.28 eV͒ quoted for Ta 2 O 5 in the literature. 2 When we examine some of the cases where the optical absorption or transmission data are presented, however, we note that vastly different definitions of the band gap were used, 5,[12][13][14] and the differences in the definitions account for the differences in the published values of the band gap. Using the definition in Eq.…”

Section: General Optical Propertiesmentioning

confidence: 99%

See 1 more Smart Citation

Defect dominated charge transport in amorphous Ta2O5 thin films

Fleming¹,

Lang²,

Jones³

et al. 2000

Journal of Applied Physics

209

View full text Add to dashboard Cite

Ta 2 O 5 is a candidate for use in metal-oxide-metal ͑MOM͒ capacitors in several areas of silicon device technology. Understanding and controlling leakage current is critical for successful implementation of this material. We have studied thermal and photoconductive charge transport processes in Ta 2 O 5 MOM capacitors fabricated by anodization, reactive sputtering, and chemical vapor deposition. We find that the results from each of these three methods are similar if one compares films that have the same thickness and electrodes. Two types of leakage current are identified: ͑a͒ a transient current that charges the bulk states of the films and ͑b͒ a steady state activated process involving electron transport via a defect band. The transient process involves either tunneling conductivity into states near the Fermi energy or ion motion. The steady state process, seen most commonly in films Ͻ300 Å thick, is dominated by a large number of defects, ϳ10 19-10 20 cm Ϫ3 , located near the metal-oxide interfaces. The interior of thick Ta 2 O 5 films has a substantially reduced number of defects. Modest heating ͑300-400°C͒ of Ta 2 O 5 in contact with a reactive metal electrode such as Al, Ti, or Ta results in interfacial reactions and the diffusion of defects across the thickness of the film. These experiments show that successful integration of Ta 2 O 5 into semiconductor processing requires a better understanding of the impact of defects on the electrical characteristics and a better control of the metal-Ta 2 O 5 interface.

show abstract

Section: General Optical Propertiesmentioning

confidence: 69%

Section: General Optical Propertiesmentioning

confidence: 99%

Defect dominated charge transport in amorphous Ta2O5 thin films

Fleming¹,

Lang²,

Jones³

et al. 2000

Journal of Applied Physics

209

View full text Add to dashboard Cite

show abstract

“…Generally, these values are comparable to values usually reported for both polycrystalline and amorphous films ). [7,26]. As it has been shown in [11], X-ray diffraction measurements provide evidence that as-deposited layers are amorphous whereas crystalline Ta 2 O 5 (orthorhombic, β-Ta 2 O 5 phase) was obtained after oxygen annealing at 1123 K. Therefore, there is not an evidence for changing of E g as a result of some kind of crystallization effects and the obtained values of E g correspond in fact to amorphous as well as to polycrystalline Ta 2 O 5 .…”

Section: Resultsmentioning

confidence: 99%

Optical characteristics of thin rf sputtered Ta₂O₅ layers

Babeva

Atanassova

Koprinarova

2005

Physica Status Solidi (a)

View full text Add to dashboard Cite

The optical properties of rf sputtered (30; 52 nm) Ta 2 O 5 before and after O 2 annealing at 1173 K have been investigated in the terms of storage capacitor applications for high density dynamic memories. Refractive index and thickness of the films are determined from transmittance and reflectance measurements at normal light incidence in the spectral range 400 -800 nm. The film density explored by refractive index is improved with increasing film thickness as well as after annealing. The optical band gap is found to be 4.20 eV for 30 nm and 4.12 eV for 52 nm Ta 2 O 5 regardless of the amorphous status of the layersamorphous (as-deposited) or polycrystalline (annealed layers).

show abstract

“…47,48 The Fresnel equations are evaluated for normal incidence, taking into account the bulk dielectric properties of the oxide layers [49][50][51][52] and of the metals. 53 Deviations from the bulk dielectric properties of the oxide and metal layers are not taken into account in the present work.…”

Section: Internal Photoemissionmentioning

confidence: 99%

Charge Transport Through Thin Amorphous Titanium and Tantalum Oxide Layers

Stella¹,

Kovacs²,

Diesing³

et al. 2011

J. Electrochem. Soc.

View full text Add to dashboard Cite

Heterosystems of metal/insulator/gold type with titanium oxide and tantalum oxide as internal barriers are studied using internal photoemission (IPE), field induced current transport (current transients after voltage steps) and chemical reaction induced current transport (chemicurrent). IPE investigations over a broad energy range from 0.8 to 4.5 eV allow a determination of the interstitial layers band gap and the maximum height of the internal tunnel barrier. The built-in field of the heterosystem is derived by the evaluation of the slope in the photoyield versus photon energy plot. Current transients recorded after voltage steps allow the determination of the heterosystems time constants which generally have a value of some milli seconds. In titanium oxide systems additional time constants with values of several 100 s appear for bias voltages >0.5 V. These time constants are assigned to slow processes altering the height of the titanium oxide barriers. and electron sources in spin polarized tunneling. 5 In the present work we present a comparative investigation of charge transport induced by different methods through thin oxide films. Charges are driven through the oxide by: i) application of a device voltage ii) illumination of the samples with monochromatic light at variable photon energies, leading to spectra of internal photoemission, iii) non adiabatic chemical surface reactions. All three methods are combined since it is possible to derive the nature of excited carriers transport through heterosystems.6 For aluminum and tantalum oxide heterosystems it was found, that they form a high pass filter for excited electrons and holes (defect electrons). 4,6 Since the height of the internal barriers for electrons and holes can be modified by an applied bias voltage, it became possible to characterize the spectra of excited charge carriers with energies below the vacuum barrier. Bias voltages of up to 1 V could be applied to the system which had an internal barrier height of 3 eV.To increase the detection efficiency for excited electrons travelling from the surface of a metal towards the bulk, one can either decrease the thickness of the top metal film of a heterosystem or one can reduce the height of the internal barrier. But with a decrease of the internal barrier the method of applying a bias voltage for tuning this barrier might become problematic, since tunnel currents become larger with lower barrier heights. Additionally, the influence of midgap states, impurities and remanent changes of the internal barrier might become more relevant for lower barriers.8,9 These problems are adressed in the present work.A comparison of metal/insulator/metal heterojunctions is presented with potentiostatically formed titanium and tantalum oxide as interjacent insulating layer. Titanium and tantalum oxide were chosen since both have bandgaps smaller than 4.5 eV.10 For amorphous tantalum oxide values of 4.2 eV are typical 11,12 whereas crystalline samples show values of 3.9-4.5 eV.12,13 Bulk titanium oxide values are for rut...

show abstract

Optical Properties of Tantalum Oxide Films on Silicon

Cited by 22 publications

References 14 publications

Defect dominated charge transport in amorphous Ta2O5 thin films

Defect dominated charge transport in amorphous Ta2O5 thin films

Optical characteristics of thin rf sputtered Ta₂O₅ layers

Charge Transport Through Thin Amorphous Titanium and Tantalum Oxide Layers

Contact Info

Product

Resources

About

Optical Properties of Tantalum Oxide Films on Silicon

Cited by 22 publications

References 14 publications

Defect dominated charge transport in amorphous Ta2O5 thin films

Defect dominated charge transport in amorphous Ta2O5 thin films

Optical characteristics of thin rf sputtered Ta2O5 layers

Charge Transport Through Thin Amorphous Titanium and Tantalum Oxide Layers

Contact Info

Product

Resources

About

Optical characteristics of thin rf sputtered Ta₂O₅ layers