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1.
The change in the thickness and chemical states of the interfacial layer and the related electrical properties in Ta2O5 films with different annealing temperatures were investigated. The high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy analyses revealed that the 700 °C-annealed Ta2O5 film remained to be amorphous and had the thinnest interfacial layer which was caused by Ta-silicate decomposition to Ta2O5 and SiO2. In addition, the electrical properties were improved after annealing treatments. Our results suggest that an annealing treatment at 700 °C results in the highest capacitance and the lowest leakage current in Ta2O5 films due to the thinnest interfacial layer and non-crystallization. 相似文献
2.
In this study, the structural and electrical properties of amorphous and crystalline Ta2O5 thin films deposited on p-type Si by low pressure metalorganic chemical vapour deposition from a Ta(OC2H5)5 source have been investigated. The as-deposited layers are amorphous, whereas crystalline Ta2O5 (hexagonal phase) was obtained after post-deposition O2-annealing at 800°C. Physico-chemical analysis of our layers shows that the O2-treatment leads to the growth of a thin (1 nm) interfacial SiO2 layer between Ta2O5 and Si but, contrary to other studies, was not sufficient to reduce the level of carbon and hydrogen contaminants. Crystalline Ta2O5 shows better leakage current properties than amorphous Ta2O5. The conduction mechanism in amorphous Ta2O5 is clearly attributed to the Poole–Frenkel effect with a barrier height separating the traps from the conduction band of 0.8 eV. For crystalline Ta2O5, the situation remains unclear since no simple law can be invoked due to the presence of the SiO2 interlayer: a double conduction process based on a tunnelling effect in SiO2 followed by a trap-modulated mechanism in Ta2O5 may be invoked. From capacitance–voltage measurements, the permittivity was found to be 25 for amorphous samples, but values ranging from 56 to 59 were found for crystalline layers, suggesting a high anisotropic character. 相似文献
3.
Matsui Y. Torii K. Hirayama M. Fujisaki Y. Iijima S. Ohji Y. 《Electron Device Letters, IEEE》1996,17(9):431-433
The electrical properties of CVD-Ta2O5 thin-films are improved by post-deposition oxygen-radical annealing. Since this annealing is carried out at very low pressure (10-6 torr), the growth of SiO2 in Ta2O 5/Si interface is small, and the residual carbon in the film is reduced. The damage to the Ta2O5 film caused by oxygen ion bombardment is negligible, because few charged particles reach the film. A critical voltage Vcrit of 1.45 V for the leakage current less than 10-8 A/cm2 was realized by these Ta2O5 films with the effective thickness teff of 2.59 nm. The Vcrit value for oxygen-radical annealing is higher than that for oxygen-plasma annealing 相似文献
4.
N-channel metal oxide semiconductor field effect transistors with Ta2O5 gate dielectric were fabricated. The Ta2O5/silicon barrier height was calculated using both the lucky electron model and the thermionic emission model. Based on the lucky electron model, a barrier height of 0.77 eV was extracted from the slope of the ln(Ig/Id) versus ln(Isub/Id) plot using an impact ionization energy of 1.3 eV. Due to the low barrier height, the application of Ta2 O5 gate dielectric transistors is limited to low supply voltage preferably less than 2.0 V 相似文献
5.
In this brief, we present a post-deposition annealing technique that employs furnace annealing in N2O (FN2O) to reduce the leakage current of chemical-vapor-deposited tantalum penta-oxide (CVD Ta2O5) thin films. Compared with furnace annealing in O2 (FO) and rapid thermal annealing in N 2O (N2O), FN2O annealing proved to have the lowest leakage current and the most reliable time-dependent dielectric breakdown (TDDB) 相似文献
6.
A capacitor technology developed to obtain extremely thin Ta2 O5 dielectric film with an effective SiO2 film thickness down to 3 nm (equivalent to 11 fF/μm2) for a 1.5-V, low-power, high-density, 64-Mb DRAM is discussed. The Ta2 O5 has low leakage current, low defect density, and excellent step coverage. The key process is two-step annealing after the deposition of the film by thermal chemical vapor deposition (CVD). The first step involves ozone (O3) annealing with ultraviolet light irradiation, which reduces the leakage current. The second step is dry oxygen (O2) annealing, which decreases the defect density. A more significant reduction in the leakage current is attained by the combination of the two annealing steps 相似文献
7.
D. Spassov 《Microelectronic Engineering》2008,85(1):214-222
The influence of the rapid thermal annealing (RTA) in vacuum at 1000 °C on the leakage current characteristics and conduction mechanisms in thermal Ta2O5 (7-40 nm) on Si has been studied. It was established that the effect of RTA depends on both the initial parameters of the films (defined by the oxidation temperature and film thickness) and annealing time (15-60 s). The RTA tends to change the distribution and the density of the traps in stack, and this reflects on the dielectric and leakage properties. The thinner the film and the poorer the oxidation, the more susceptible the layer to heating. The short (15 s) annealing is effective in improving the leakage characteristics of poorly oxidized samples. The RTA effect, however, is rather deleterious than beneficial, for the thinner layers with good oxygen stoichiometry. RTA modifies the conduction mechanism of Ta2O5 films only in the high-field region. The annealing time has strong impact on the appearance of a certain type of reactions upon annealing resulting to variation of the ratio between donors and traps into Ta2O5, causing different degree of compensation, and consequently to domination of one of the two mechanisms at high fields (Schottky emission or Poole-Frenkel effect). Trends associated with simultaneous action of annealing and generation of traps during RTA processing, and respectively the domination of one of them, are discussed. 相似文献
8.
《Electron Device Letters, IEEE》1998,19(11):441-443
As the gate oxide thickness decreases below 2 nm, the gate leakage current increases dramatically due to direct tunneling current. This large gate leakage current will be an obstacle to reducing gate oxide thickness for the high speed operation of future devices. A MOS transistor with Ta2O5 gate dielectric is fabricated and characterized as a possible replacement for MOS transistors with ultra-thin gate silicon dioxide. Mobility, Id-Vd, Id-Vg, gate leakage current, and capacitance-voltage (C-V) characteristics of Ta2O5 transistors are evaluated and compared with SiO2 transistors. The gate leakage current is three to five orders smaller for Ta2O5 transistors than SiO2 transistors 相似文献
9.
E Atanassova D SpassovA Paskaleva J KoprinarovaM Georgieva 《Microelectronics Journal》2002,33(11):907-920
The effect of the oxidation temperature (673-873 K) on the microstructural and electrical properties of thermal Ta2O5 thin films on Si has been studied. Auger electron spectroscopy and X-ray photoelectron spectroscopy results revealed that the films are non-stoichiometric in the depth; an interfacial transition layer between tantalum oxide and Si substrate, containing presumably SiO2 was detected. It has been found by X-ray diffraction that the amorphous state of Ta2O5 depends on both the oxidation temperature and the thickness of the films—the combination of high oxidation temperature (>823 K) and thickness smaller than 50 nm is critical for the appearance of a crystal phase. The Ta2O5 layers crystallize to the monoclinic phase and the temperature of the phase transition is between 773 and 823 K for the thinner layers (<50 nm) and very close to 873 K for the thicker ones. The electrical characterization (current/voltage; capacitance/voltage) reveals that the optimal oxidation temperature for achieving the highest dielectric constant (∼32) and the lowest leakage current (10−8 A/cm2 at 1 MV/cm applied field) is 873 K. The results imply that the poor oxidation related defects are rather the dominant factor in the leakage current than the crystallization effects. 相似文献
10.
The degradation of Ta2O5-based (10 nm) stacked capacitors with different top electrodes, (Al, W, Au) under constant current stress has been investigated. The variation of electrical characteristics after the stress is addressed to gate-induced defects rather than to poor-oxidation related defects. The main wearout parameter in Ta2O5 stacks is bulk-related and a generation only of bulk traps giving rise to oxide charge is observed. The post-stress current–voltage curves reveal that stress-induced leakage current (SILC) mode occurs in all capacitors and the characteristics of pre-existing traps define the stress response. The results are discussed in terms of simultaneous action of two competing processes: negative charge trapping in pre-existing electron traps and stress-induced positive charge generation, and the domination of one of them in dependence on both the stress level and the gate used. The charge build-up and the trapping/detrapping processes modify the dominant conduction mechanism and the gate-induced defects are precursors for device degradation. It is concluded that the impact of the metal gate on the ultimate reliability of high-k stacked capacitors should be strongly considered. 相似文献
11.
Qiang Lu Donggun Park Kalnitsky A. Chang C. Chia-Cheng Cheng Sing Pin Tay Tsu-Jae King Chenming Hu 《Electron Device Letters, IEEE》1998,19(9):341-342
Capacitors with ultra-thin (6.0-12.0 nm) CVD Ta2O5 film were fabricated on lightly doped Si substrates and their leakage current (Ig-Vg) and capacitance (C-V) characteristics were studied. For the first time, samples with stack equivalent oxide thickness around 2.0 nm were compared with ultra-thin silicon dioxide and silicon oxynitride. The Ta2O5 samples showed remarkably lower leakage current, which not only verified the advantages of ultra-thin Ta2O5 as dielectrics for high density DRAM's, but also suggested the possibility of its application as the gate dielectric material in MOSFET's 相似文献
12.
E. Atanassova N. Novkovski D. Spassov A. Paskaleva A. Skeparovski 《Microelectronics Reliability》2014
The Time-Dependent-Dielectric Breakdown (TDDB) characteristics of MOS capacitors with Hf-doped Ta2O5 films (8 nm) have been analyzed. The devices were investigated by applying a constant voltage stress at gate injection, at room and elevated temperatures. Stress voltage and temperature dependences of hard breakdown of undoped and Hf-doped Ta2O5 were compared. The doped Ta2O5 exhibits improved TDDB characteristics in regard to the pure one. The maximum voltage projected for a 10 years lifetime at room temperature is −2.4 V. The presence of Hf into the matrix of Ta2O5 modifies the dielectric breakdown mechanism making it more adequate to the percolation model. The peculiarities of Weibull distribution of dielectric breakdown are discussed in terms of effect of three factors: nature of pre-existing traps and trapping phenomena; stress-induced new traps generation; interface layer degradation. 相似文献
13.
I. Mani?E. Atanassova N. Stojadinovi?D. Spassov A. Paskaleva 《Microelectronic Engineering》2011,88(3):305-313
The stress-induced leakage current in Hf-doped Ta2O5 layers (7; 10 nm) under constant voltage stress at gate injection was investigated in order to assess the mechanisms of conduction, the traps involved and the effect of Hf doping. The amount of Hf is found to affect the conduction mechanisms, the temperature dependence of the leakage current and the current response to the stress. A significant leakage current increase is observed only when the stress voltage and/or stress time exceed the corresponding threshold values, where the charge trapping at the pre-existing traps dominates below and defect generation above these threshold values. The energy levels of the traps responsible for the current transport are estimated. The stress effect on dominant conduction mechanisms appears quite weak, and the nature of the traps controlling the current transport before and after the stress seems to be nearly identical. The results indicate that the constant voltage stress affects the pre-existing traps in Hf-doped Ta2O5 and modifies their parameters, but there is no evidence for stress-induced generation of traps with completely new nature different from oxygen-vacancy related defects. 相似文献
14.
A novel antiresonant reflecting optical waveguide (ARROW) fabricated using both the organic and dielectric thin film technologies is presented for the first time. The ARROW consisted of the fluorinated polyimide and tantalum pentoxide (Ta2O5) hybrid layers deposited on a Si substrate. For TE polarized light, the propagation loss of the waveguide as low as 0.8 dB/cm is obtained at 632.8 nm. The propagation loss for TM polarized light is 2.7 dB/cm. Some design considerations of the hybrid ARROW are also discussed in this work 相似文献
15.
Stress-induced leakage currents (SILCs) in thin Ta2O5 films after short- and long-term constant current stress (CCS) at both gate polarities at different levels of injected current were investigated. The behavior of the SILCs and the change of quasistatic C–V characteristics after the degradation confirmed the variations of gate voltage with time during CCS necessary to maintain the injected current density through the oxide.The conduction mechanisms were also investigated. Initially, normal Poole–Frenkel (PF) mechanism dominates in the oxide at medium fields (0.4– 1.7 MV/cm) independently of the deposition temperature or annealing steps. After the degradation modified PF with different compensation factors appears. After long-term degradation conduction mechanism goes back to PF. 相似文献
16.
Tantalum pentoxide (Ta2O5) deposited by pulsed DC magnetron sputtering technique as the gate dielectric for 4H-SiC based metal-insulator-semiconductor (MIS) structure has been investigated. A rectifying current-voltage characteristic was observed, with the injection of current occurred when a positive DC bias was applied to the gate electrode with respect to the n type 4H-SiC substrate. This undesirable behavior is attributed to the relatively small band gap of Ta2O5 of around 4.3 eV, resulting in a small band offset between the 4H-SiC and Ta2O5. To overcome this problem, a thin thermal silicon oxide layer was introduced between Ta2O5 and 4H-SiC. This has substantially reduced the leakage current through the MIS structure. Further improvement was obtained by annealing the Ta2O5 at 900 °C in oxygen. The annealing has also reduced the effective charge in the dielectric film, as deduced from high frequency C-V measurements of the Ta2O5/SiO2/4H-SiC capacitors. 相似文献
17.
A dielectric film technology characterized by a novel multilayer structure formed by oxidation of Ta2O5/Si3 N4 films on polysilicon has been developed to realize high-density dRAMs. The dry oxidation of the Ta2O5/Si3N4 layers was performed at temperatures higher than 900°C. This film has a capacitance per unit area from 5.5 to 6.0 fF/ μm2, which is equivalent to that of a 6.0- to 6.5-nm-thick SiO2. The leakage current at an effective electric field of 5 MV/cm is less than 10-9 A/cm2. Under such an electric field, the extrapolated time to failure for 50% cumulative failure can be as high as 1000 years 相似文献
18.
Tantalum pentoxide films (13–260 nm) on p-type Si have been prepared by thermal oxidation at 673–873 K of rf sputtered Ta films and have been studied using Al–Ta2O5–Si capacitors. Both dielectric constant and refractive index were found to depend on the thickness of the Ta2O5 layers. Layers with a dielectric constant of 25–32 were obtained. A decreasing trend in the leakage current was found upon increasing oxidation temperature from 673 to 873 K. Leakage current density of (10−8 to 3×10−7) A cm−2 at 1 MV cm−1 effective field was achieved. 相似文献
19.
M. Macatrão C.P.L. Rubinger L.C. Costa T. Monteiro N. Franco B.Z. Saggioro A.C. Hernandes 《Microelectronics Journal》2009,40(2):309-67
Structural, spectroscopic and dielectric properties of thulium-doped laser-heated pedestal Ta2O5 as-grown fibres were studied. Undoped samples grow preferentially with a single crystalline monoclinic structure. The fibre with the lowest thulium content (0.1 at%) also shows predominantly a monoclinic phase and no intra-4f12 Tm3+ recombination was observed. For sample with the highest thulium amount (1.0 at%), the appearance of a dominant triclinic phase as well as intraionic optical activation was observed. The dependence of photoluminescence on excitation energy allows identification of different site locations of Tm3+ ions in the lattice. The absence of recombination between the first and the ground-state multiplets as well as the temperature dependence of the observed transitions was justified by an efficient energy transfer between the Tm3+ ions. Microwave dielectric properties were investigated using the small perturbation theory. At a frequency of 5 GHz, the undoped material exhibits a dielectric permittivity of 21 and for thulium-doped Ta2O5 samples it decreases to 18 for the highest doping concentration. Nevertheless, the dielectric losses maintain a very low value. 相似文献
20.
A hybrid polyimide/Ta2O5/polyimide antiresonant reflecting optical waveguide (ARROW) is presented. The ARROW consists of fluorinated polyimide and tantalum pentoxide hybrid layers deposited on Si substrates. The propagation losses of the device are 0.6 and 2.6 dB/cm at 1.3 μm for TE and TM polarised lights, respectively 相似文献