Influence of Process Parameters on Resistive Switching in MOCVD NiO Films
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Influence of Process Parameters on Resistive Switching in MOCVD NiO Films X.P. Wang1, D.J. Wouters1,3, M. Toeller2, J. Meersschaut1, L. Goux1, Y.Y. Chen3, B. Govoreanu1, L. Pantisano1, R. Degraeve1, M. Jurczak1, L. Altimime1, J. Kittl1 1
IMEC, Kapeldreef 74, B-3001 Leuven, Belgium Tokyo Electron Limited, Akasaka Biz Tower, 3-1 Akasaka 5-chome, Minato-ku, Tokyo 1076325 Japan 3 Department of Electrical Engineering (ESAT), Katholieke Universiteit Leuven, B-3001 Leuven, Belgium 2
ABSTRACT The unipolar resisitive switching properties of MOCVD deposited NiO in Ni/NiO/TiN stacks is reported. The switching quality is defined as function of RESET current and Roff/Ron ratio, and the importance of the Forming current and voltage on these parameters is discussed. The effect of structural stack variations as NiO thickness, Ti doping, and TiN thickness on the switching behavior of NiO is explained by the effect on the forming current and voltage conditions, and on Joule heating dissipation. Thinner NiO films, Ti doping, as well as thicker top electrode improve the switching quality by decreasing the RESET current and increasing the Roff/Ron ratio. INTRODUCTION NiO has become one of the prototype metal-oxide resistive switching materials since the publication of Baek et al. [1]. While the most widely used fabrication technique for formation of NiO has been reactive physical vapor deposition, for scaled RRAM integration more advanced and conformal chemical vapor deposition techniques are required. We report on the unipolar switching properties of NiO synthesized by Metal-Organic Chemical Vapor Deposition technique (MOCVD) , and the effects of process parameters as NiO thickness, of Ti-doping, and of electrode thickness on the switching performance is discussed. NiO DEPOSITION NiO and Ti-doped NiO films were deposited by MOCVD on Ni coated 300mm Si substrates (20nm PVD Ni on top of 40nm PVD TiN/Si), using Ni(dmamb)2 and Ti(TDMAT) precursors and O2 in a MOCVD chamber on a TEL-TRIAS platform [2]. Deposition temperature was 315oC. Within wafer uniformity was better than 1.5%, and surface roughness less than 1nm for 10nm thick films. Density of the NiO films is 6.55g/cm3, which is close to bulk value. The films were polycrystalline with a preferred (111) orientation from XRD. From ERD analysis, films were shown to be near stoechiometric but slightly Ni rich with the Ni:O ratio of 1.1:0.9. Tidoped NiO films up to 1.75%Ti were successfully deposited by adding Ti precursor pulses.
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TEST STRUCTURE AND ELECTRICAL TEST CONDITIONS Unipolar switching was observed on these MOCVD and ALD NiO films using Ni as top or bottom electrode and TiN as the counter electrode. For process integration reasons, we selected Ni as the uniform bottom electrode while TiN top electrode(PVD) was patterned using a conventional litho and reactive dry etching process. Top electrode size was 100um*100um. For studying the effect of process parameters, we changed thickness of the NiO, compared undoped and Ti-doped NiO films, and investigated different thicknesses
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