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1160-H14-11

Conformal MOCVD Deposition of GeSbTe in High Aspect Ratio Via Structures for Phase Change Memory Applications J. F. Zheng1, P.Chen1, W. Hunks1, M. Stender1, C. Xu1, W. Li1, J.Roeder1 S. Kamepalli2, C. Schell2, J. Reed2, J. Ricker2, R. Sandoval2, J. Fournier2, W.Czubatyj2, G. Wicker2, C. Dennison2, S. Hudgens2, T. Lowrey2 1

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ATMI Inc., 7 Commerce Drive, Danbury, CT 06810 Ovonyx Technologies, Inc, 2956 Waterview Drive, Rochester Hills, MI 48309

ABSTRACT We have demonstrated conformal deposition of amorphous GeSbTe films in high aspect ratio structures by MOCVD. SEM analysis showed the as-deposited GeSbTe films had smooth morphologies and were well controlled for void free amorphous conformal deposition. GeSbTe films adhere well to SiO2, TiN, and TiAlN. The morphology and adhesion are stable in 420ºC post process. By annealing at 365ºC, amorphous GeSbTe films converted into crystalline GeSbTe with polycrystalline grain sizes of 5nm. Film resistivity in the crystalline phase ranged from 0.001 to 0.1 Ω-cm, suitable for device applications. Phase change devices fabricated with confined via structures filled with MOCVD GeSbTe showed cycle endurances up to 1x1010 with a dynamic set/rest resistance of two orders of magnitude. INTRODUCTION Since its invention by Ovshinsky, PCM (Phase Change Memory) based on GST alloys (e.g. Ge2Sb2Te5) has become one of the most promising candidates for coming generation nonvolatile memory applications due to its scalability when compared with current charge based memory [1]. Certain DRAM applications are feasible due to the demonstrated high intrinsic cycle endurance, speed, and path for reduction of reset current [2-4]. Planar PCM devices made by Physical Vapor Deposition (PVD) of GST alloys demonstrated good characteristics of phase change behavior, with performance surpassing the requirements for flash memory [5]. PCM in a confined cell structure with high aspect ratio (> 3:1) and sub-100nm diameters have been filled with Chemical Vapor Deposition (CVD) deposited GST and have substantial advantages over cell designs with planar structures made by PVD deposited GST alloys [3,4]. In a CVD GST based confined PCM cell of dash shape with a cross-section of 7.5nm x 60nm and depth of 30nm, a low reset current of 160uA, high cycling endurance of 1x1010, and fast set speed of 50ns have been demonstrated [4]. The key factor is the conformal filling of very high aspect ratio confined structure by CVD or Atomic Layer Deposition (ALD) [6, 7]. Successful adoption of CVD or ALD deposited GST materials for PCM applications will require suitable material properties in addition to achieving a conformal fill of the confined structures. These requirements include: void free deposition, good adhesion to SiO2 and top or bottom metal electrode, material properties stable at 400ºC to survive subsequent device processing steps, low resistivity in the crystalline state, and possess a wide resistivity range between the amorphous and crystalline phases, which is desired for Multi-Level-Cell (MLC) app