Ulfrathin Tantalum Oxide Capacitor Process Using Oxygen‐Plasma Annealing

Kamiyama, Satoshi; Suzuki, Hiroshi; Watanabe, H.; Sakai, Akira; Kimura, H.; Мizuki, J.

doi:10.1149/1.2054904

Cited by 69 publications

(13 citation statements)

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“…6 for different values of E 0 . The intersection of the calculated curves with the horizontal line given by sl th ¼ sl 1 gives possible values for the internal field E b . The relation between E 0 and E b is shown in the inset of Fig.…”

Section: -63mentioning

confidence: 99%

Charge Transport Through Thin Amorphous Titanium and Tantalum Oxide Layers

Stella¹,

Kovacs²,

Diesing³

et al. 2011

J. Electrochem. Soc.

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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...

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Section: -63mentioning

confidence: 99%

Charge Transport Through Thin Amorphous Titanium and Tantalum Oxide Layers

Stella¹,

Kovacs²,

Diesing³

et al. 2011

J. Electrochem. Soc.

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“…The leading candidates for alternative high-k insulators in future DRAMs (beyond 100 nm node) include single metal oxides. Among them tantalum pentoxide with a dielectric constant greater than 20 and relatively low leakage currents appears to be one of the best candidates [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Successful attempts have been made for applying Ta 2 O 5 as a storage capacitor in highly integrated DRAMs [2,3,7,8].…”

Section: Introductionmentioning

confidence: 99%

“…Among them tantalum pentoxide with a dielectric constant greater than 20 and relatively low leakage currents appears to be one of the best candidates [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Successful attempts have been made for applying Ta 2 O 5 as a storage capacitor in highly integrated DRAMs [2,3,7,8]. The major focus on Ta 2 O 5 films research is to improve the leakage currents and dielectric constant -the two most important parameters for the material to be used as memory dielectric in dynamic memories [1,2,4,[6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…Successful attempts have been made for applying Ta 2 O 5 as a storage capacitor in highly integrated DRAMs [2,3,7,8]. The major focus on Ta 2 O 5 films research is to improve the leakage currents and dielectric constant -the two most important parameters for the material to be used as memory dielectric in dynamic memories [1,2,4,[6][7][8][9][10]. In order to improve these parameters detailed studying of microstructural, electrical and optical properties in close relation with technological conditions is needed.…”

Section: Introductionmentioning

confidence: 99%

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Optical characteristics of thin rf sputtered Ta₂O₅ layers

Babeva

Atanassova

Koprinarova

2005

Physica Status Solidi (a)

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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).

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“…Experimental (100) p-type silicon wafers (8.5-11.5 ⍀ cm) were used as the starting material. The silicon wafers were first deposited with 500 nm of chemical vapor deposited tungsten using WF 6 and SiH 4 as reactants. The Ta 2 O 5 film was then deposited in an O 2 ambiant at 400ЊC.…”

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confidence: 99%

Leakage Current Mechanism of Metal ‐ Ta2 O 5 ‐ Metal Capacitors for Memory Device Applications

Lai

Lee

1999

J. Electrochem. Soc.

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In recent years, Ta 2 O 5 has been researched due to its high dielectric constant. It has gained attention for its application on storage capacitors for dynamic random access memory (DRAM), gate oxide 1 and lightly doped drain spacer 2 for future deep submicrometer metal oxide semiconductor field effect transistors (MOSFETs). In the past, efforts have been made to deposit Ta 2 O 5 on polysilicon bottom electrodes using different deposition systems and annealing processes. [3][4][5][6][7][8][9][10][11][12][13] However, poor electrical properties of Ta 2 O 5 deposited by low pressure chemical vapor deposition (LPCVD) were often obtained when carbon-based Ta(OC 2 H 5 ) 5 was used as the precursor in the mass production processes. 4-8 Therefore, many oxygen annealing processes such as dry-O 2 rapid thermal annealing (RTA), 8 O 2 -plasma annealing, 4-6 two-step annealing, 3 UV-O 3 annealing, 3 and N 2 O RTA 9 or furnace N 2 O annealing 10 were studied extensively. Although the leakage current density was well suppressed by these annealing processes mentioned above, it also accompanied a decay in dielectric constant. [8][9][10] This was due to the formation of a very thin SiO 2 layer about 2 nm between Ta 2 O 5 and the polysilicon interface after a high temperature annealing process. The capacitance was decreased due to the additional low dielectric constant SiO 2 layer. 9,10 This problem could be lessened by using refractory metal electrode such as tungsten. However, the leakage current level of 1 ϫ 10 Ϫ7 A/cm 2 at 1 V was at least one order of magnitude larger than that of Ta 2 O 5 deposited on polysilicon by LPCVD. 4 In this work, high quality thin Ta 2 O 5 films (14 nm) are deposited by PECVD on tungsten bottom electrode using a pentaethoxytantalum Ta(OC 2 H 5 ) 5 as the precursor. Material properties are investigated by X-ray diffraction (XRD) and secondary ion mass spectroscopy (SIMS). The electrical measurements, including current-voltage (I-V) and capacitance-voltage (C-V) characteristics are performed on Au/Ta 2 O 5 /W/p-Si devices. The current conduction mechanism of Ta 2 O 5 films is investigated. A comparison is also made between Ta 2 O 5 films deposited by PECVD and LPCVD. Experimental (100) p-type silicon wafers (8.5-11.5 ⍀ cm) were used as the starting material. The silicon wafers were first deposited with 500 nm of chemical vapor deposited tungsten using WF 6 and SiH 4 as reactants. The Ta 2 O 5 film was then deposited in an O 2 ambiant at 400ЊC. Ta 2 O 5 films were deposited on separate silicon wafers simultaneously to measure the refractive index and the film thickness. The Ta(OC 2 H 5 ) 5 was vaporized in the source tank in the temperature range of 140 to 170ЊC and was carried to the deposition chamber using nitrogen as the carrier gas. The precursor was then transferred to the reactor through a gas heating line. The gas heating line was maintained at a higher temperature of 160 to 190ЊC to prevent recondensation of Ta(OC 2 H 5 ) 5 . The chamber was maintained at 0.3 to 0.4 Torr during deposition. T...

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Ulfrathin Tantalum Oxide Capacitor Process Using Oxygen‐Plasma Annealing

Cited by 69 publications

References 0 publications

Charge Transport Through Thin Amorphous Titanium and Tantalum Oxide Layers

Charge Transport Through Thin Amorphous Titanium and Tantalum Oxide Layers

Optical characteristics of thin rf sputtered Ta₂O₅ layers

Leakage Current Mechanism of Metal ‐ Ta2 O 5 ‐ Metal Capacitors for Memory Device Applications

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Ulfrathin Tantalum Oxide Capacitor Process Using Oxygen‐Plasma Annealing

Cited by 69 publications

References 0 publications

Charge Transport Through Thin Amorphous Titanium and Tantalum Oxide Layers

Charge Transport Through Thin Amorphous Titanium and Tantalum Oxide Layers

Optical characteristics of thin rf sputtered Ta2O5 layers

Leakage Current Mechanism of Metal ‐ Ta2 O 5 ‐ Metal Capacitors for Memory Device Applications

Contact Info

Product

Resources

About

Optical characteristics of thin rf sputtered Ta₂O₅ layers