| 1. |
- Dezelah, Charles L., et al.
(författare)
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A low valent metalorganic precursor for the growth of tungsten nitride thin films by atomic layer deposition
- 2007
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 17:11, s. 1109-1116
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Tidskriftsartikel (refereegranskat)abstract
- The atomic layer deposition growth of tungsten nitride films was demonstrated using the precursors W-2(NMe2)(6) and ammonia with substrate temperatures between 150 and 250 degrees C. At 180 degrees C, surface saturative growth was achieved with W-2(NMe2)(6) pulse lengths of >= 2.0 s. The growth rates were between 0.74 and 0.81 angstrom cycle(-1) at substrate temperatures between 180 and 210 degrees C. Growth rates of 0.57 and 0.96 angstrom cycle(-1) were observed at 150 and 220 degrees C, respectively. In a series of films deposited at 180 degrees C, the film thicknesses varied linearly with the number of deposition cycles. Films grown at 180 and 210 degrees C exhibited resistivity values between 810 and 4600 mu Omega cm. Time-of-flight elastic recoil detection analysis on tungsten nitride films containing a protective AlN overlayer demonstrated slightly nitrogen-rich films relative to W2N, with compositions of W1.0N0.82C0.13O0.26H0.33 at 150 degrees C, W1.0N0.74C0.20O0.33H0.28 at 180 degrees C, and W1.0N0.82C0.33O0.18H0.23 at 210 degrees C. In the absence of an AlN overlayer, the oxygen and hydrogen levels were much higher, suggesting that the films degrade in the presence of ambient atmosphere. The as-deposited films were amorphous. Amorphous films containing a protective AlN overlayer were annealed to 600 - 800 degrees C under a nitrogen atmosphere. X-Ray diffraction patterns suggested that crystallization does not occur at or below 800 degrees C. Similar annealing of films that did not contain the AlN overlayer afforded X-ray diffraction patterns that were consistent with orthorhombic WO3. Atomic force microscopy showed root-mean-square surface roughnesses of 0.9, 0.8, and 0.7 nm for films deposited at 150, 180, and 210 degrees C, respectively.
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| 2. |
- Dezelah, Charles L., et al.
(författare)
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The Atomic Layer Deposition of HfO2 and ZrO2 using Advanced Metallocene Precursors and H2O as the Oxygen Source
- 2008
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Ingår i: Chemical Vapor Deposition. - : Wiley. - 0948-1907 .- 1521-3862. ; 14:11-12, s. 358-365
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Tidskriftsartikel (refereegranskat)abstract
- The atomic layer deposition (ALD) of HfO2 and ZrO2 thin films is investigated using (MeCp)(2)HfMe2, (MCp)(2)Hf(OMe)(Me), (MeCp)(2)ZrMe2, and (MeCp)(2)Zr(OMe)(Me) as the precursors at deposition temperatures between 300 and 500 degrees C, with water vapor as the oxygen Source. A self-limiting growth mechanism is confirmed at 350 degrees C for all the metal precursors examined. The processes provide nearly stoichiometric HfO2 and ZrO2 films with carbon and hydrogen concentrations below 0.5 and 1.0 at.-%, respectively, for representative samples. All films are polycrystalline as deposited, and possess a thin interfacial SiO2 layer. The capacitance-voltage (C-V) and Current density-voltage (I-V) behavior is reported and discussed for capacitor structures containing films from this study.
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| 3. |
- Jogi, Indrek, et al.
(författare)
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Atomic layer deposition of high capacitance density Ta2O5-ZrO2 based dielectrics for metal-insulator-metal structures
- 2010
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Ingår i: Microelectronic Engineering. - : Elsevier BV. - 0167-9317 .- 1873-5568. ; 87:2, s. 144-149
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated electrical properties of laminated atomic layer deposited films: ZrO2-Ta2O5, ZrO2-Nb2O5-Ta2O5, ZrO2-TaxNb1-xO5 and Ta2O5-ZrxNbyOz. Even though the capacitances of laminates were often higher compared to films of constituent materials with similar thickness, considerably higher charge storage factors, Q were achieved only when tetragonal ZrO2 was stabilized in ZrO2-Ta2O5 laminate and when the laminate thickness exceeded 50 rim. The decreased Q values in the case of most laminates were the result of increased leakage currents. In the case of thinner films only Ta2O5-ZrxNbyOz, stack possessed capacitance density and Q value higher than reference HfO2. Concerning the conduction mechanisms, in the case of thinner films, the Ta2O5 or TaxNb1-xO5 apparently controlled the leakage either by Richardson-Schottky emission or Poole-Frenkel effect. (C) 2009 Elsevier B.V. All rights reserved
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| 4. |
- Jogi, Indrek, et al.
(författare)
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Investigation of ZrO2-Gd2O3 Based High-k Materials as Capacitor Dielectrics
- 2010
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 157:10, s. G202-G210
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Tidskriftsartikel (refereegranskat)abstract
- Atomic layer deposition (ALD) of ZrO2-Gd2O3 nanolaminates and mixtures was investigated for the preparation of a high permittivity dielectric material. Variation in the relative number of ALD cycles for constituent oxides allowed one to obtain films with controlled composition. Pure ZrO2 films possessed monoclinic and higher permittivity cubic or tetragonal phases, whereas the inclusion of Gd2O3 resulted in the disappearance of the monoclinic phase. Changes in phase composition were accompanied with increased permittivity of mixtures and laminates with low Gd content. Further increase in the lower permittivity Gd2O3 content above 3.4 cat. % resulted in the decreased permittivity of the mixtures. Leakage currents generally decreased with increasing Gd content, whereby laminated structures demonstrated smaller leakage currents than mixed films at a comparable Gd content. Concerning the bottom electrode materials, the best results in terms of permittivity and leakage currents were achieved with Ru, allowing a capacitance equivalent oxide thickness of similar to 1 nm and a current density of 3 X 10(-8) A/cm(2) at 1 V. Charge storage values up to 60 nC/mm(2) were obtained for mixtures and laminates with thickness below 30 nm. In general, at electric fields below 2-3 MV/cm, normal and trap-compensated Poole-Frenkel conduction mechanisms were competing, whereas at higher fields, Fowler-Nordheim and/or trap-assisted tunneling started to dominate.
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| 5. |
- Jogi, Indrek, et al.
(författare)
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Precursor-dependent structural and electrical characteristics of atomic layer deposited films : Case study on titanium oxide
- 2006
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Ingår i: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 9:6, s. 1084-1089
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Tidskriftsartikel (refereegranskat)abstract
- Thin (10-20 nm) TiO2 films were atomic layer deposited from TiCl4, Ti(OC2H5)(4), H2O and H2O2 in the substrate temperature range 125-350 degrees C. The structure, chemical composition and electrical properties were correlated to the process temperature and nature of precursors, whereas the effect of precursors on conduction mechanisms was considerable only in the films grown at 125 degrees C, otherwise controlled by oxide-electrode interfaces. The use of chloride resulted in films with highest permittivity while the use of hydrogen peroxide resulted in lowest permittivity but also in lowest leakage. The post-deposition (pre-metallization) annealing resulted in densification and (re)crystallization of TiO2 layer but also in thickening of low-permittivity interface layers.
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| 6. |
- Kukli, Kaupo, et al.
(författare)
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Atomic Layer Deposition and Characterization of HfO2 Films on Noble Metal
- 2005
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Ingår i: Journal of The Electrochemical Society. - : The Electrochemical Society. - 0013-4651. ; 152:7, s. F75-F82
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Tidskriftsartikel (refereegranskat)abstract
- HfO2 films were grown by atomic layer deposition from HfCl4 and H2O on atomic layer deposited 40-70 nm thick platinum, iridium, and ruthenium films in the temperature range 200-600°C. The phase formed in the 30-50 nm thick HfO2 films was monoclinic HfO2 dominating over amorphous material without noticeable contribution from metastable crystallographic polymorphs. The metal-dielectric-metal capacitor structures formed after evaporating Al gate electrodes demonstrated effective permittivity values in the range 11-16 and breakdown fields reaching 5 MV/cm. Iridium electrode films showed the highest stability in terms of reliability and reproducibility of dielectric characteristics.
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| 7. |
- Kukli, Kaupo, et al.
(författare)
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Atomic layer deposition of Ru films from bis(2,5-dimethylpyrrolyl)ruthenium and oxygen
- 2012
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 520:7, s. 2756-2763
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Tidskriftsartikel (refereegranskat)abstract
- Ru thin films were grown on hydrogen terminated Si, SiO2, Al2O3, HfO2, and TiO2 surfaces by atomic layer deposition from bis(2,5-dimethylpyrrolyl)ruthenium precursor and oxygen. The 4-20 nm thick films on these surfaces consisted of nanocrystalline hexagonal metallic ruthenium, regardless of the deposition temperature. At the lowest temperatures examined, 250-255 degrees C, the growth of the Ru films was favored on silicon, compared to the growth on Al2O3, TiO2 and HfO2. At higher temperatures the nucleation and growth of Ru became enhanced in particular on HfO2, compared to the process on silicon. At 320-325 degrees C, no growth occurred on Si-H and SiO2-covered silicon. Resistivity values down to 18 mu Omega.cm were obtained for ca. 10 nm thick Ru films.
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| 8. |
- Kukli, Kaupo, et al.
(författare)
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Atomic Layer Deposition of Ruthenium Films on Strontium Titanate
- 2011
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Ingår i: Journal of Nanoscience and Nanotechnology. - : American Scientific Publishers. - 1533-4880 .- 1533-4899. ; 11:9, s. 8378-8382
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Tidskriftsartikel (refereegranskat)abstract
- Atomic layer deposition of ruthenium on SrTiO(3) layers was investigated using (C(2)H(5)C(5)H(4)) center dot (NC(4)H(4))Ru and air as precursors. For comparison, the growth was studied also on ZrO(2) films and SiO(2)/Si surfaces. Deposition temperature was 325 degrees C. Using rather short but intense air pulses, smooth and uniform Ru films were deposited on SrTiO(3). The films were crystallized at early stages of the growth. The nucleation density and rate on SrTiO(3) were notably lower compared to that on ZrO(2) and SiO(2), but the physical qualities including the film conductivity were considerably enhanced after reaching Ru film thickness around 10 nm.
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| 9. |
- Kukli, Kaupo, et al.
(författare)
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Effect of selected atomic layer deposition parameters on the structure and dielectric properties of hafnium oxide films
- 2004
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Ingår i: Journal of Applied Physics. ; 96:9, s. 5298-5307
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Tidskriftsartikel (refereegranskat)abstract
- Hf02 films were atomic layer deposited from HfCl4 and H20 onSi(lOO) in the temperature range of 226-750 °C. The films consisted of dominantly the monoclinic polymorph. Elastic recoildetection analysis revealed high residual chlorine and hydrogen contents (2-5 at. %) in the films grown below 300-350 °C. The content of residual hydrogen and chlorine monotonouslydecreased with increasing growth temperature. The effctive permittivity insignificantly depended on thegrowth temperature and water partial pressure. Capacitance-voltage curves exhibited market hysteresis especially in the films grown at 400-450 ° C, and demonstrated enhanced distortions likely due to the increased trap densities in the films grown at 700-750 °C. Changes in water pressure led to some changes in the extent of crystallization, but did not induce any clear change; in the capacitance of the dielectric layer.
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| 10. |
- Kukli, Kaupo, et al.
(författare)
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Engineering structure and properties of hafnium oxide films by atomic layer deposition temperature
- 2005
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090. ; 479:1-2, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- HfO2 films were atomic layer deposited from HfCl4 and H2O on Si(100) in the temperature range of 300–600 °C. At low temperatures, films grow faster and are structurally more disordered, compared to films grown at high temperatures. At high temperatures, the films are better crystallized, but grow slower and contain grain boundaries extending from substrate to gate electrode. Film growth rate and capacitance of HfO2 dielectric layers was improved by depositing stacked structures with polycrystalline films of higher purity at 600 °C on thin HfO2 sublayer grown on Si at 300 °C.
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