Seminar-Tailored Functional Oxides for Memory Applications
duygu at stanford.edu
Mon Mar 8 11:11:04 PST 2010
Tailored Functional Oxides for Memory Applications
Dr. Koen Martens
Friday, March 12th, 2010, 2:30 pm
In this project at IMEC the goal is to evaluate the possible use of Metal-Insulator Transition (MIT) materials for use in memory and transistor applications. The first material of choice, one of the most prominent metal-to-insulator transition materials is the transition metal oxide vanadium oxide. Several phases of this oxide exhibit a transition between a metallic and semiconducting state with changing temperature, doping content or by applying a light pulse or electric field. The physical nature of this MIT phenomenon is under debate. The question is whether the MIT in e.g. VO2 is caused by a Peierls (phonon assisted) or Mott transition (due to an electron correlation effect). Harnessing a purely electronic Mott transition in a memory would imply a number of significant benefits: 1) very fast operation (< ~ps) 2) excellent scalability (uniformity, no filament formation as in typical RRAM) 3) good endurance (no material transport). In this project we aim to develop thin films of MIT materials (vanadium oxide), integrate them into MIM and TFT-type devices, characterize their properties and evaluate their potential for memory and transistor applications.
V2O5 films are grown by means of ALD and V films are grown by means of DC sputtering. The ALD process has been shown to be conformal in 100nm size contact holes for integration into MIM capacitors. Reduction of the obtained V2O5 films to V6O13 and VO2 (B) phases has been shown to be possible by means of reducing thermal treatments in FGA and N2 ambient. The influence of the substrate will be discussed. However, the VO2 M1 phase, which shows the MIT at 68C, is not obtainable in this way by means of reduction in these gases at atmospheric pressure. Vanadium metal films have been oxidized. At atmospheric pressure V2O5 is obtained, as expected. Morphology issues and reduction behavior will be treated regarding oxidized vanadium films. Alternative ALD processes and annealing treatments will be discussed as well as electrical properties of the vanadium oxide films.
Koen Martens received the B.S. and M.S. degrees in Electrical Engineering from the Katholieke Universiteit Leuven, Belgium, in 2001 and 2004. In january 2009 he obtained a PhD degree on the topic of germanium MOSFETs at the Katholieke Universiteit Leuven, Belgium and at IMEC. In 2006 he was on an internship at Stanford University working on the electrical characterization of germanium MOSFETs. Currently he is working as an FWO sponsored postdoctoral researcher on functional oxides with tailored properties for nanoelectronics with a focus on oxides showing a metal-to-insulator transition and RRAM.
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