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Chemical vapor deposition of manganese nitride

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Doctoral research project on depositing thin layers of manganese nitride for future computer chips.

Doctoral research project on depositing thin layers of manganese nitride for future computer chips.


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  • 1. Chemical Vapor Deposition of Manganese Nitride Teresa S. Spicer, PhD, PMP teresa.s.spicer@gmail.com http://www.linkedin.com/in/teresaspicer • Doctoral research performed at the Department of Materials Science and Engineering at the University of Illinois at Urbana-Champaign, in collaboration with chemistry students in Dr. Gregory S. Girolami’s research group • Submitted to Chemistry of Materials for publication, published in doctoral thesis in October 2009 Amount of assumed background knowledge and information: Assumed knowledge areas: Basic chemistry and physics knowledge, chemical nomenclature, ball and stick structures, lability due to spin states, the basics of chemical vapor deposition as a technique, familiarity with a variety of materials characterization techniques and ability to interpret the raw data from them
  • 2. Outline Introduction Problem Statement Experiments Results Key Findings
  • 3. Introduction
  • 4. Integrated circuits have created a vital industry and enabled the telecommunications revolution Global Semiconductors Market Value, $ billion, 2004-2013(e) 350 9 J 8 Market value (USD billions) 300 7 250 J J J 6 J % Growth 200 5 J 150 4 J 3 100 J J 2 50 1 0 0 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 Source: Datamonitor Image from http://www.textually.org/ Semiconductor industry plays an important role in globalization, and therefore also in shaping our collective future.
  • 5. Miniaturization drives integrated circuit development and applications Image from http://tunicca.wordpress.com/2009/07/21/moores-law-the-effect-on-productivity/
  • 6. Materials and thin film processing are key to miniaturization 2007: 30 new materials introduced into 45-nm node1 1 A Thorough Examination of the Electronic Chemicals and Materials Markets, Businesswire, August 15, 2007 Image from http://www.intel.com/pressroom/kits/45nm/photos.htm ❝The implementation of high-k and metal materials marks the biggest change in transistor technology since the introduction of polysilicon gate MOS transistors in the late 1960s.❞ Gordon Moore, Intel Co-Founder, regarding two of the 30 new materials introduced in 2007 In order to continue miniaturization, thin films of new materials are required.
  • 7. Manganese nitride CVD could be used in both electronic and spintronic devices Magnetic layers in microelectronics • Mn4N is ferrimagnetic • Mn3N2, MnN are antiferromagnetic http://static.howstuffworks.com/gif/recover-data-hard-drive-2.jpg Mn doping of GaN for spintronics • Ga1-xMnxN is a magnetic semiconductor at RT • Current Mn source: Manganocene, high T required http://www.wmi.badw-muenchen.de/research/images/electron.jpg
  • 8. Synthetic inorganic chemistry and materials engineering are required for new CVD processes Synthetic inorganic Materials engineering chemistry Conception and synthesis of new CVD of films from precursor CVD precursor candidates Process hypothesis development Synthesis of modified precursor Measurement of film properties Development of novel growth processes and chemistry are needed to develop good CVD processes.
  • 9. Problem Statement
  • 10. Many previous transition metal nitrides have been deposited from amides reacted with ammonia Tried-and-true concept: R R N N M N + H H R R H Example: Tetrakis(dimethylamido)-titanium(IV) + NH3 → TiN films1-4 1 Dubois, L. H.; Zegarski, B. R.; Girolami, G. S. J. Electrochem. Soc. 1992, 3 Prybyla, J. A.; Chiang, C. M.; Dubois, L. H. J. Electrochem. Soc. 1993, 2695– 3603–3609. 2702. 2 Dubois, L. H. Polyhedron 1994, 13, 1329–1336. 4 Fix, R. M.; Gordon, R. G.; Hoffman, D. M. Chem. Mat. 1990, 235–41. Dialkylamide precursors in particular have worked very well in the past.
  • 11. Previously, few volatile precursors for Mn-N were known Shannon-Prewitt Crystal Ionic Radii of Cations1 Most common oxidation state shown in bold.1 Scandium Titanium Vanadium Chromium Manganese Iron Cobolt Nickel Copper Zinc 21 22 23 24 25 26 27 28 29 30 Sc Ti V Cr Mn Fe Co Ni Cu Zn 44.956 47.867 50.942 51.996 54.938 55.845 58.933 58.693 63.546 65.39 +3 +2 +2 +2 +2 +2 +2 +2 +2 +2 88 pm 100 pm 93 pm 94 pm 97 pm 92 pm 88 pm 83 pm 91 pm 88 pm +3 +3 +3 +3 +3 +3 +3 +3 81 pm 78 pm 75 pm 78 pm 78 pm 75 pm 74 pm 87 pm +4 +4 +4 +4 +4 +4 74 pm 72 pm 69 pm 67 pm 72 pm 67 pm +5 +6 +7 68 pm 58 pm 60 pm 1 Wulfsberg, G. Principles of Descriptive Inorganic Chemistry. University Science Books, Sausalito, CA, 1991. Due to the size of Mn(II), sterically bulky ligands are required to prevent di- or polymerization of the precursor.
  • 12. Bis[di(tert-butyl)amido]manganese(II) is a monomer and volatile 30% probability surfaces shown. Spicer, C. W. Synthesis, Characterization and Chemical Vapor Deposition of Transition Metal Di(tert-butyl)amido Compounds. Doctoral dissertation, University of Illinois at Urbana-Champaign: Urbana, IL, 2008. When reacted with ammonia, bis[di(tert-butyl)amido]Mn(II) should give manganese nitride films.
  • 13. Experiments
  • 14. Films were deposited with and without ammonia Deposition in vacuum chamber ➡ In-situ ellipsometer monitors growth ➡ Precursor heated to 40 ºC ➡ N2 carrier gas H N H Experiment sets: Substrates: H With NH3 • Si(100) • Varying T, constant NH3 flow • α-C TEM grids • Varying NH3 flow, constant T Experiment set: Substrates: Without NH3 • Cr-coated Si(100) • Varying T
  • 15. Film phase, composition, roughness, and microstructure data were collected Deposition in vacuum chamber ➡ In-situ ellipsometer monitors growth ➡ Precursor heated to 40 ºC ➡ N2 carrier gas With NH3 Without NH3 Atomic force microscopy X-ray diffraction Transmission electron microscopy* Scanning electron microscopy X-ray photoelectron spectroscopy Auger electron spectroscopy * Select films
  • 16. Results
  • 17. The growth rates are high considering the low growth temperatures Ammonia flow: 4.3 sccm Precursor partial pressure: 0.2 - 0.4 mTorr Total chamber pressure: 1.6 mTorr The reaction between bis[di(tert-butyl)]amidoMn(II) and ammonia is very facile.
  • 18. In the absence of ammonia, severely carbon- contaminated films of Mn are obtained Auger electron spectrum of Mn film grown at 300 ºC 41.5 at. % C 38.4 at. % O 20.0 at. % Mn Ammonia is key to growing films of manganese nitride.
  • 19. The reaction is likely a transamination First step of tetrakis(dimethylamido)Ti(IV) transamination Me Me Me Me N N Me Me Me H Me N Ti N + NH3 N Ti N + H N Me N Me Me N H Me Me Me Me Me Analogous first step of bis[di(tert-butyl)amidoMn(II) transamination t-Bu t-Bu t-Bu H t-Bu N Mn N + NH3 N Mn N + H N t-Bu t-Bu t-Bu H t-Bu The analogous results in other respects suggest that the reaction mechanism is also analogous.
  • 20. Films can be deposited at temperatures as low as 80ºC in the presence of ammonia H N H H With NH3 Without NH3 • No growth until 400 ºC • Even at 400 ºC, growth rate is only 0.4 nm/min 500 nm • Growth rate is 2.1 nm/min The reaction between bis[di(tert-butyl)]amidoMn(II) and ammonia is very facile.
  • 21. The film phase and composition depend on growth temperature XRD diffractograms (101) η-Mn3N2 AES-derived elemental Mn2N1.08 compositions (420) (422) Mn23C6 (611) (440) (531) (102) (110) (0 0 10) Mn Intensity (Arbitraty units) N C 35 40 45 50 55 60 65 70 75 80 85 2-theta (103) (110) (202) (213) (206) (006) (200) The film grown at 300 ºC is markedly different from those grown at 200 ºC and below.
  • 22. 80-100 ºC: Crystalline grains of η-Mn3N2 embedded in an amorphous matrix XRD diffractogram Brightfield TEM image Insets: convergent-beam diffraction patterns from nm- sized areas indicated in image The extremely low growth temperature inhibits complete crystallization of the films at 80 and 100 ºC.
  • 23. 200ºC: Fully crystalline films of η-Mn3N2 TEM images and patterns Left: Convergent-beam diffraction patterns from six different nm-sized areas Below: Brightfield image with diffraction pattern inset XRD diffractogram The high-quality crystallinity at merely 200 ºC is unusual.
  • 24. 300 ºC: 40% Mn3N2, 40% Mn2N1.08, 20% Mn23C6 XRD diffractogram (101) (103) (420) 900 (422) η-Mn3N2 800 Mn2N1.08 700 Mn23C6 Intensity (counts) 1 µm 600 (110) (006) 500 (611) 400 AES elemental composition 300 (440) (102) (202) • 67% Mn 200 (531) (200) (110) (0 0 10) 100 (213) (206) • 16% N 0 • 17% C 35 40 45 50 55 60 65 70 75 80 85 2-theta At 300 ºC, the ammonia supply may have been insufficient to deposit a single phase.
  • 25. The crystallinity and high growth rates can be attributed to high-spin Mn(II) High growth rates for low temperatures Low-temperature crystallinity Any growth at 80ºC is surprising, especially at Convergent-beam diffraction patterns from rates of several nanometers a minute six different nm-sized areas, all showing diffraction through crystalline η-Mn3N2 6 J 5 Growth rate (nm/min) J 4 J 3 2 J 1 0 0 50 100 150 200 250 300 350 Deposition temperature (ºC) Surface species are likely to remain reactive and mobile and can settle into low-energy ordered arrangements.
  • 26. Key Findings
  • 27. CVD of Manganese Nitride • Very facile, due to the lability of high-spin Mn(II) • Transamination of precursor with ammonia • Films of η-Mn3N2 films can be grown at 80ºC
  • 28. Acknowledgements Dr. Charles Spicer, UNCC Dr. Bong-Sub Lee, UIUC Kristof Darmawikarta, UIUC Dr. Angel Yanguas-Gil, UIUC Dr. Mauro Sardela, UIUC Nancy Finnegan, UIUC (Ret.) Dr. Tim Spila, UIUC Dr. Richard Haasch, UIUC Subhash Gujrathi, Université de Montreal Research supported by NSF grant DMR-0420768 Film characterization was carried out in the Center for Microanalysis of Materials, University of Illinois, which is partially supported by the U.S. Department of Energy under grant DEFG02-91-ER45439