Atomic Layer Deposition of Oxide Thin Films with Metal Alkoxides as Oxygen Sources
10.1126/science.288.5464.319
Crossref journal-article
American Association for the Advancement of Science (AAAS)
Science (221)
Abstract

A chemical approach to atomic layer deposition (ALD) of oxide thin films is reported here. Instead of using water or other compounds for an oxygen source, oxygen is obtained from a metal alkoxide, which serves as both an oxygen and a metal source when it reacts with another metal compound such as a metal chloride or a metal alkyl. These reactions generally enable deposition of oxides of many metals. With this approach, an alumina film has been deposited on silicon without creating an interfacial silicon oxide layer that otherwise forms easily. This finding adds to the other benefits of the ALD method, especially the atomic-level thickness control and excellent uniformity, and takes a major step toward the scientifically challenging and technologically important task of replacing silica as the gate dielectric in the future generations of metal oxide semiconductor field effect transistors.

Bibliography

Ritala, M., Kukli, K., Rahtu, A., Räisänen, P. I., Leskelä, M., Sajavaara, T., & Keinonen, J. (2000). Atomic Layer Deposition of Oxide Thin Films with Metal Alkoxides as Oxygen Sources. Science, 288(5464), 319–321.

Authors 7
  1. Mikko Ritala (first)
  2. Kaupo Kukli (additional)
  3. Antti Rahtu (additional)
  4. Petri I. Räisänen (additional)
  5. Markku Leskelä (additional)
  6. Timo Sajavaara (additional)
  7. Juhani Keinonen (additional)
References 22 Referenced 441
  1. G. Moore IEDM Tech. Dig. (1975) p. 11. (10.1038/256011a0)
  2. Semiconductor Industry Association National Technology Roadmap for Semiconductors: Technology Needs (Sematech Austin TX 1997). See also www.itrs.net/ntrs/publntrs.nsf.
  3. Schulz M., Nature 399, 729 (1999). (10.1038/21526) / Nature by Schulz M. (1999)
  4. Packan P. A., Science 285, 2079 (1999). (10.1126/science.285.5436.2079) / Science by Packan P. A. (1999)
  5. Muller D. A., et al., Nature 399, 758 (1999). (10.1038/21602) / Nature by Muller D. A. (1999)
  6. The gate metal-oxide-semiconductor structure may be thought of as a parallel plate capacitor with capacitance C = ε r ε 0 A / d where ε r is the relative permittivity of the oxide ε 0 is the permittivity of a vacuum A is the area of the capacitor and d is the thickness of the oxide.
  7. Hubbard K. J., Schlom D. G., J. Mater. Res. 11, 2757 (1996). (10.1557/JMR.1996.0350) / J. Mater. Res. by Hubbard K. J. (1996)
  8. Wilk G. D., Wallace R. M., Appl. Phys. Lett. 74, 2854 (1999). (10.1063/1.124036) / Appl. Phys. Lett. by Wilk G. D. (1999)
  9. 10.1103/PhysRevLett.81.3014
  10. Niinistö L., Ritala M., Leskelä M., Mater. Sci. Eng. B 41, 23 (1996). (10.1016/S0921-5107(96)01617-0) / Mater. Sci. Eng. B by Niinistö L. (1996)
  11. Ritala M., Appl. Surf. Sci. 112, 223 (1997). (10.1016/S0169-4332(96)01004-5) / Appl. Surf. Sci. by Ritala M. (1997)
  12. 10.1126/science.278.5345.1934
  13. Klaus J. W., Sneh O., Ott A. W., George S. M., Surf. Rev. Lett. 6, 435 (1999). (10.1142/S0218625X99000433) / Surf. Rev. Lett. by Klaus J. W. (1999)
  14. Ritala M., et al., Chem. Vap. Deposition 5, 7 (1999). (10.1002/(SICI)1521-3862(199901)5:1<7::AID-CVDE7>3.0.CO;2-J) / Chem. Vap. Deposition by Ritala M. (1999)
  15. Corriou R., Leclercq D., Lefèrve P., Mutin P. H., Vioux A., Chem. Mater. 4, 961 (1992). (10.1021/cm00023a001) / Chem. Mater. by Corriou R. (1992)
  16. Vioux A., Chem. Mater. 9, 2292 (1997). (10.1021/cm970322a) / Chem. Mater. by Vioux A. (1997)
  17. Trentler T. J., Denler T. E., Bertone J. F., Agrawal A., Colvin V. L., J. Am. Chem. Soc. 121, 1613 (1999). (10.1021/ja983361b) / J. Am. Chem. Soc. by Trentler T. J. (1999)
  18. The films were deposited in a flow type F-120 ALD reactor (Microchemistry Espoo Finland) operated under a pressure of about 10 mbar. Nitrogen was used as a carrier and as a purging gas. The compounds Al(CH 3 ) 3 and Si(OEt) 4 were evaporated in external sources and led into the reactor through a solenoid valve. The other compounds were evaporated inside the reactor at temperatures that correspond to a vapor pressure of about 0.1 mbar. The source vapors were pulsed onto the substrates by means of inert gas valving. Glass and silicon were used as substrates. Film thicknesses were evaluated from transmission spectra and elemental analyses were carried out at the accelerator laboratory in Helsinki by TOF-ERDA with the use of 53-MeV 127 I 10+ ions as projectiles.
  19. Bourget L., Corriou R. J. P., Leclercq D., Mutin P. H., Vioux A., J. Non-Cryst. Solids 242, 81 (1998). (10.1016/S0022-3093(98)00789-3) / J. Non-Cryst. Solids by Bourget L. (1998)
  20. Outokumpu HSC Chemistry for Windows program version 4.0 Outokumpu Research Oy Pori Finland.
  21. For comparison with the conventional ALD processes the dielectric properties were mainly measured with In 2 O 3 :Sn-insulator-Al capacitor structures because that was the standard procedure in earlier studies. The insulators were made 100 to 200 nm thick so that the measured permittivity and leakage reflect the properties of the film bulk rather than the interfaces in these specific capacitors. For an Al 2 O 3 film made by the new process from AlCl 3 and Al(O i Pr) 3 a permittivity of 7.5 and a leakage current density of 10 –7 A/cm 2 at an electric field of 2.0 MV/cm were measured. The corresponding values for an Al 2 O 3 film made by the conventional ALD process from Al(CH 3 ) 3 and H 2 O were 8.2 and 10 –6 A/cm 2 for the permittivity and the leakage current density respectively. Likewise Ta 2 O 5 made from TaCl 5 and Ta(OEt) 5 had a permittivity of 20 to 24 whereas the conventional processes result in permittivities of 24 to 25 (Et ethyl). The leakages in these films were on equivalent levels. The Zr 0.45 Ti 0.55 O 2 film deposited at 300°C with the new chemistry was partly crystallized and had a high permittivity of 43 but like the high permittivity materials in general it possessed a rather high leakage current of 10 –6 A/cm 2 at an electric field of 0.2 MV/cm. In contrast when deposited at 250°C the film was completely amorphous had a permittivity of 17 and had a greatly reduced leakage such that the level of 10 –6 A/cm 2 was achieved with an electric field of only 1 to 2 MV/cm. However with this material no direct comparison to the conventional ALD processes can be made.
  22. Supported by the Academy of Finland and the Finnish National Technology Agency (TEKES).
Dates
Type When
Created 23 years, 1 month ago (July 27, 2002, 5:40 a.m.)
Deposited 1 year, 7 months ago (Jan. 13, 2024, 5:27 a.m.)
Indexed 1 day, 12 hours ago (Aug. 31, 2025, 7:17 p.m.)
Issued 25 years, 4 months ago (April 14, 2000)
Published 25 years, 4 months ago (April 14, 2000)
Published Print 25 years, 4 months ago (April 14, 2000)
Funders 0

None

@article{Ritala_2000, title={Atomic Layer Deposition of Oxide Thin Films with Metal Alkoxides as Oxygen Sources}, volume={288}, ISSN={1095-9203}, url={http://dx.doi.org/10.1126/science.288.5464.319}, DOI={10.1126/science.288.5464.319}, number={5464}, journal={Science}, publisher={American Association for the Advancement of Science (AAAS)}, author={Ritala, Mikko and Kukli, Kaupo and Rahtu, Antti and Räisänen, Petri I. and Leskelä, Markku and Sajavaara, Timo and Keinonen, Juhani}, year={2000}, month=apr, pages={319–321} }