THIN Ta2O5 LAYERS ON Si AS AN ALTERNATIVE TO SiO2 FOR HIGH-DENSITY DRAM APPLICATIONS

Atanassova, E.; Dimitrova, T.

doi:10.1016/b978-012513910-6/50055-4

Cited by 43 publications

(53 citation statements)

References 81 publications

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“…4, confirms that the influence of T s is essential in the range 300-350°C, where n arises with 0.12, achieving the value of 1.98, similar to values reported for as-fabricated Ta 2 O 5 films obtained by other methods. 6,7,16,27 Further, the highest T s does not lead to any increase of refractive index at 633 nm. Obviously, the dense enough as-grown oxides can be achieved at T s = 350-400°C.…”

Section: B Xrd Resultsmentioning

confidence: 92%

“…Since R is a periodical function of nd with a periodicity of / 2, it changes with variation of nd from zero to / 4, and depends on the ratio between refractive index n of the layer and of the substrate, n sub , respectively, ͑R decreases when n / n sub Ͻ 1 and vice versa͒. If we suppose that the values of n are close to 2-2.2, which are the typical values of stoichiometric Ta 2 O 5 , 7,16,25 the optical thickness will vary from /8 to / 18 in the whole spectral range and it will be generally smaller than / 4. Considering that n / n sub Ͻ 1, ͑n sub = 5.60-3.66 in the used spectral range for Si wafer͒, the decay of R could be attributed to the increase of optical thickness.…”

Section: B Xrd Resultsmentioning

confidence: 99%

“…2 In consequence, a number of compatible methods such as rf sputtering, thermal oxidation of Ta film, a variety of chemical-vapor deposition techniques, ionbeam deposition, atomic layer deposition, pulsed laser deposition have been developed to fabricate Ta 2 O 5 films. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Investigations on the production methodology continue in competition with alternative solution and each method exhibits advantages and disadvantages in terms of, mainly, electrical properties that are essential for DRAM applications. It is not yet clear which method will be chosen as the best one with respect to the storage capacitor applications because each fabricated method strongly affects the structural and electrical properties of the Ta 2 O 5 .…”

Section: Introductionmentioning

confidence: 99%

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Structural and optical characteristics of tantalum oxide grown by pulsed Nd:YAG laser oxidation

Atanassova

Aygün

Turan

et al. 2006

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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Embedded argon as a tool for sampling local structure in thin plasma deposited aluminum oxide films J. Appl. Phys. 112, 103306 (2012) Tantalum pentoxide ͑Ta 2 O 5 ͒ thin films ͑20-50 nm͒ have been grown by 1064 nm Nd:YAG laser oxidation of Ta film deposited on Si. The chemical bonding, structure, and optical properties of the films have been studied by Fourier transform infrared spectroscopy, x-ray diffraction, and reflectance measurements at normal light incidence in the spectral range of 350-800 nm. The effect of the substrate temperature ͑250-400°C͒ during oxidation and its optimization with respect to the used laser beam energy density ͑3.2-3.4 J / cm 2 per pulse͒ is discussed. It is established that the substrate temperature is a critical factor for the effectiveness of the oxidation process and can be used to control the composition and amorphous status of the films. The film density explored by refractive index is improved with increasing film thickness. The refractive index of the layers grown under the higher laser beam energy density and at substrate temperature of 350-400°C was found to be close to the value of bulk Ta 2 O 5 . The films are amorphous at substrate temperature below 350°C and possessed an orthorhombic ͑␤-Ta 2 O 5 ͒ crystal structure at higher temperatures. The thinner layers crystallize at a little higher temperature.

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Section: B Xrd Resultsmentioning

confidence: 92%

Section: B Xrd Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structural and optical characteristics of tantalum oxide grown by pulsed Nd:YAG laser oxidation

Atanassova

Aygün

Turan

et al. 2006

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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“…Between the high-dielectrics tantalum pentoxide (Ta 2 O 5 ) [7] has been identified as very good solution for dynamic random access memories (DRAM) [8]. In this work we specifically study the case of Ta 2 O 5 .…”

Section: Introductionmentioning

confidence: 99%

“…After chemical cleaning, a Ta film was deposited on Si by sputtering of a Ta target in Ar atmosphere. Subsequently, the Ta film was oxidized in dry O 2 at 600 ∘ C. More details on the sample preparation can be found in [8]. The above oxidation temperature was chosen so as to be low enough to minimize the substrate oxidation in order to prevent the formation of tantalum silicides.…”

Section: Fabrication Of the Samplesmentioning

confidence: 99%

Frequency Dependence of C-V Characteristics of MOS Capacitors Containing Nanosized High-κ Ta₂O₅ Dielectrics

Novkovski¹,

Atanassova²

2017

Advances in Materials Science and Engineering

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Capacitance of metal-insulator-Si structures containing high permittivity dielectric exhibits complicated behaviour when voltage and frequency dependencies are studied. From our study on metal (Al, Au, W)-Ta 2 O 5 /SiO 2 -Si structures, we identify serial C-R measurement mode to be more convenient for use than the parallel one usually used in characterization of similar structures. Strong frequency dependence that is not due to real variations in the dielectric permittivity of the layers is observed. Very high capacitance at low frequencies is due to the leakage in Ta 2 O 5 layer. We found that the above observation is mainly due to different leakage current mechanisms in the two different layers composing the stack. The effect is highly dependent on the applied voltage, since the leakage currents are strongly nonlinear functions of the electric field in the layers. Additionally, at low frequencies, transition currents influence the measured value of the capacitance. From the capacitance measurements several parameters are extracted, such as capacitance in accumulation, effective dielectric constant, and oxide charges. Extracting parameters of the studied structures by standard methods in the case of high-/interfacial layer stacks can lead to substantial errors. Some cases demonstrating these deficiencies of the methods are presented and solutions for obtaining better results are proposed.

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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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THIN Ta2O5 LAYERS ON Si AS AN ALTERNATIVE TO SiO2 FOR HIGH-DENSITY DRAM APPLICATIONS

Cited by 43 publications

References 81 publications

Structural and optical characteristics of tantalum oxide grown by pulsed Nd:YAG laser oxidation

Structural and optical characteristics of tantalum oxide grown by pulsed Nd:YAG laser oxidation

Frequency Dependence of C-V Characteristics of MOS Capacitors Containing Nanosized High-κ Ta₂O₅ Dielectrics

Optical characteristics of thin rf sputtered Ta₂O₅ layers

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THIN Ta2O5 LAYERS ON Si AS AN ALTERNATIVE TO SiO2 FOR HIGH-DENSITY DRAM APPLICATIONS

Cited by 43 publications

References 81 publications

Structural and optical characteristics of tantalum oxide grown by pulsed Nd:YAG laser oxidation

Structural and optical characteristics of tantalum oxide grown by pulsed Nd:YAG laser oxidation

Frequency Dependence of C-V Characteristics of MOS Capacitors Containing Nanosized High-κ Ta2O5 Dielectrics

Optical characteristics of thin rf sputtered Ta2O5 layers

Contact Info

Product

Resources

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Frequency Dependence of C-V Characteristics of MOS Capacitors Containing Nanosized High-κ Ta₂O₅ Dielectrics

Optical characteristics of thin rf sputtered Ta₂O₅ layers