共查询到20条相似文献,搜索用时 11 毫秒
1.
Shinriki H. Kisu T. Kimura S.-I. Nishioka Y. Kawamoto Y. Mukai K. 《Electron Devices, IEEE Transactions on》1990,37(9):1939-1947
To ensure the required capacitance for low-power DRAMs (dynamic RAMs) beyond 4 Mb, three kinds of capacitor structures are proposed: (a) poly-Si/SiO2/Ta2O5/SiO2 /poly-Si or poly-Si/Si3N4/Ta2O 5/SiO2/poly-Si (SIS), (b) W/Ta2O5 /SiO2/poly-Si (MIS), and (c) W/Ta2O5 W (MIM). The investigation of time-dependent dielectric breakdown and leakage current characteristics indicates that capacitor dielectrics that have equivalent SiO2 thicknesses of 5, 4, and 3 nm can be applied to 3.3-V operated 16-Mb DRAMs having stacked capacitor cells (STCs) by using SIS, MIS, and MIM structures, respectively, and that 3 and 1.5 nm can be applied to 1.5-V operated 64-Mb DRAMs having STCs by using MIS and MIM structures, respectively. This can be accomplished while maintaining a low enough leakage current for favorable refresh characteristics. In addition, all these capacitors show good heat endurance at 950°C for 30 min. Therefore, these capacitors allow the fabrication of low-power high-density DRAMs beyond 4 Mb using conventional fabrication processes at temperatures up to 950°C. Use of the SIS structure confirms the compatability of the fabrication process of a storage capacitor using Ta2O5 film and the conventional DRAM fabrication processes by successful application to the fabrication process of an experimental memory array with 1.5-μm×3.6-μm stacked-capacitor DRAM cells 相似文献
2.
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
3.
E. Atanassova 《Microelectronics Reliability》1999,39(8):1185
Tantalum pentoxide thin films on Si prepared by two conventional for modern microelectronics methods (RF sputtering of Ta in Ar + O2 mixture and thermal oxidation of tantalum layer on Si) have been investigated with respect to their dielectric, structural and electric properties. It has been found that the formation of ultra thin SiO2 film at the interface with Si, during fabrication implementing the methods used, is unavoidable as both, X-ray photoelectron spectroscopy and electrical measurements, have indicated. The initial films (as-deposited and as-grown) are not perfect and contain suboxides of tantalum and silicon which act as electrical active centers in the form of oxide charges and interface states. Conditions which guarantee obtaining high quality tantalum oxide with dielectric constant of 32–37 and leakage current density less than 10−7 A/cm2 at 1.5 V applied voltage (Ta2O5 thickness equivalent to about 3.5 nm of SiO2) have been established. These specifications make the layers obtained suitable alternative to SiO2 for high density DRAM application. 相似文献
4.
《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
5.
Tantalum pentoxide thin layers (10–100 nm) obtained by thermal oxidation of rf sputtered Ta films on Si have been investigated with respect of their dielectric, structural and electric properties. It is established that stoichiometric Ta2O5 detected at the surface of the layers is reduced to tantalum suboxides in their depth. The oxide parameters are discussed in terms of a presence of an unavoidable ultrathin SiO2 between Si and Ta2O5 and bond defects in both the oxide and the interface transition region. Conditions which guarantee obtaining high quality tantalum oxide with a dielectric constant of 32–35 and a leakage current less than 10−7–10−8 A/cm2 at 1.5 V (SiO2 equivalent thickness of 2.5–3 nm) are established. These specifications make the layers obtained suitable alternative to SiO2 for high density DRAMs application. 相似文献
6.
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
7.
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
8.
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
9.
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
10.
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
11.
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
12.
The present status, successes, challenges and future of Ta2O5, and mixed Ta2O5-based high-k layers as active component in storage capacitors of nanoscale DRAMs are discussed. The engineering of new Ta2O5-based dielectrics (doped Ta2O5 and multicomponent Ta2O5-based high-k dielectrics) as well as of metal/high-k interface in MIM capacitor configuration are identified as critical factors for further reduction of EOT value below 1 nm. 相似文献
13.
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
14.
The effect of various electrodes (Al, W, TiN) deposited by evaporation (Al) and sputtering (W, TiN) on the electrical characteristics of Ta2O5 stack capacitors has been investigated. The leakage currents, breakdown fields, mechanism of conductivity and dielectric constant are discussed in the terms of possible reactions between Ta2O5 and electrode material as well as electrode-deposition-process-induced defects acting as electrically active centers. During deposition of TiN and Al a reaction that worsens the properties of Ta2O5 occurs while there is not an indication for detectable reduction of Ta2O5 when top electrode is W. The sputtered W top electrode is a good candidate as a gate of storage capacitors in DRAMs, but sputtering technique is less suitable for deposition of TiN due to the introduction of radiation defects causing deterioration of leakage current. Although some reaction between Al and Ta2O5 occurs, the resulting electrical properties of the capacitors are still acceptable. 相似文献
15.
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
16.
Silicon MOS transistors having amorphous Ta2O5 insulator gates have been fabricated. The Ta2O5 films were deposited using a low pressure (a few mtorr) plasma-enhanced CVD process in a microwave (2.45 GHz) excited electron cyclotron resonance reactor. The source gas was TaF5. Electrical characteristics of p-channel Al gate transistors are presented 相似文献
17.
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
18.
Lightly Al-doped Ta2O5 films (10;15 nm) obtained by rf sputtering have been studied with respect to their dielectric and electrical properties. The formed metal-high-k dielectric-semiconductor capacitors have been characterized by capacitance-voltage and temperature-dependent current-voltage characteristics. It was established that the introduction of small amount (5 at.%) Al into the matrix of Ta2O5 improves dielectric constant, introduces negative oxide charge, suppresses deep oxygen-vacancy centers in Ta2O5 but creates shallow traps and changes the dominant conduction mechanism in the stacks. The doping produces more leaky films at room temperature and lower current at high temperature as compared to the case of pure Ta2O5. It is concluded that the strong contribution of tunneling processes through shallow traps in the conductivity of doped films could explain the observed current degradation at room temperature and its improved temperature stability at high temperatures. The energy levels of the traps responsible for the current transport are estimated. 相似文献
19.
The effect of various electrodes (Al, W, TiN) deposited by evaporation (Al) and sputtering (W, TiN) on the electrical characteristics of thermal thin film (15-35 nm) Ta2O5 capacitors has been investigated. The absolute level of leakage currents, breakdown fields, mechanism of conductivity, dielectric constant values are discussed in the terms of possible reactions between Ta2O5 and electrode material as well as electrode deposition process-induced defects acting as electrically active centers. The dielectric constant values are in the range 12-26 in dependence on both Ta2O5 thickness and gate material. The results show that during deposition of TiN and Al a reaction that worsens the properties of Ta2O5 occurs while there is not an indication for detectable reduction of Ta2O5 when top electrode is W, and the leakage current is 5-7 orders of magnitude lower as compared to Al and TiN-electroded capacitors. The high level of leakage current for TiN and Al gate capacitors are related to the radiation defects generated in Ta2O5 during sputtering of TiN, and damaged interface at the electrode due to a reaction between Al and Ta2O5, respectively. It is demonstrated that the quality of the top electrode affects the electrical characteristics of the capacitors and the sputtered W is found to be the best. The sputtered W gate provides Ta2O5 capacitors with a good quality: the current density <7 × 10−10 A/cm2 at 1 V (0.7 MV/cm, 15 nm thick Ta2O5). W deposition is not accompanied by an introduction of a detectable damage leading to a change of the properties of the initial as-grown Ta2O5 as in the case of TiN electrode. Damage introduced during TiN sputtering is responsible for current deterioration (high leakage current) and poor breakdown characteristics. It is concluded that the sputtered W top electrode is a good candidate as a top electrode of storage capacitors in dynamic random access memories giving a stable contact with Ta2O5, but sputtering technique is less suitable (favorable) for deposition of TiN as a metal electrode due to the introduction of radiation defects causing both deterioration of leakage current and poor breakdown characteristics. 相似文献
20.
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