title: Thickness effect of ultra-thin Ta2O5 resistance switching layer in 28 nm-diameter memory cell.
abstract: Resistance switching (RS) devices with ultra-thin Ta2O5 switching layer (0.5-2.0 nm) with a cell diameter of 28 nm were fabricated. The performance of the devices was tested by voltage-driven current-voltage (I-V) sweep and closed-loop pulse switching (CLPS) tests. A Ta layer was placed beneath the Ta2O5 switching layer to act as an oxygen vacancy reservoir. The device with the smallest Ta2O5 thickness (0.5 nm) showed normal switching properties with gradual change in resistance in I-V sweep or CLPS and high reliability. By contrast, other devices with higher Ta2O5 thickness (1.0-2.0 nm) showed abrupt switching with several abnormal behaviours, degraded resistance distribution, especially in high resistance state, and much lower reliability performance. A single conical or hour-glass shaped double conical conducting filament shape was conceived to explain these behavioural differences that depended on the Ta2O5 switching layer thickness. Loss of oxygen via lateral diffusion to the encapsulating Si3N4/SiO2 layer was suggested as the main degradation mechanism for reliability, and a method to improve reliability was also proposed.
authors.affiliation: Department of Materials Science and Engineering and Inter-university Semiconductor Research Center, Seoul National University, Seoul 151-744, Korea.
authors.forename: Tae Hyung
authors.initials: TH
authors.lastname: Park
authors.affiliation: Department of Materials Science and Engineering and Inter-university Semiconductor Research Center, Seoul National University, Seoul 151-744, Korea.
authors.forename: Seul Ji
authors.initials: SJ
authors.lastname: Song
authors.affiliation: Department of Materials Science and Engineering and Inter-university Semiconductor Research Center, Seoul National University, Seoul 151-744, Korea.
authors.forename: Hae Jin
authors.initials: HJ
authors.lastname: Kim
authors.affiliation: SK Hynix Inc., 2091 Gyeongchung-daero Bubal-eub Icheon-si Gyeonggi-do, 467-734, Korea.
authors.forename: Soo Gil
authors.initials: SG
authors.lastname: Kim
authors.affiliation: SK Hynix Inc., 2091 Gyeongchung-daero Bubal-eub Icheon-si Gyeonggi-do, 467-734, Korea.
authors.forename: Suock
authors.initials: S
authors.lastname: Chung
authors.affiliation: SK Hynix Inc., 2091 Gyeongchung-daero Bubal-eub Icheon-si Gyeonggi-do, 467-734, Korea.
authors.forename: Beom Yong
authors.initials: BY
authors.lastname: Kim
authors.affiliation: SK Hynix Inc., 2091 Gyeongchung-daero Bubal-eub Icheon-si Gyeonggi-do, 467-734, Korea.
authors.forename: Kee Jeung
authors.initials: KJ
authors.lastname: Lee
authors.affiliation: Hewlett-Packard Laboratories, Hewlett-Packard Company, Palo Alto, California 94304, USA.
authors.forename: Kyung Min
authors.initials: KM
authors.lastname: Kim
authors.affiliation: Department of Materials Science and Engineering, Seoul National University of Science and Technology, Seoul 139-743, Korea.
authors.forename: Byung Joon
authors.initials: BJ
authors.lastname: Choi
authors.affiliation: Department of Materials Science and Engineering and Inter-university Semiconductor Research Center, Seoul National University, Seoul 151-744, Korea.
authors.forename: Cheol Seong
authors.initials: CS
authors.lastname: Hwang
mesh_terms: D004553:Electric Conductivity; D008422:Materials Testing / Q000379:methods; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D049329:Nanostructures / Q000737:chemistry / Q000648:ultrastructure; D010087:Oxides / Q000737:chemistry*; D017655:Silicon Compounds / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D013635:Tantalum / Q000737:chemistry*
chemical_list: D010087:Oxides; D017655:Silicon Compounds; D013635:Tantalum; D012822:Silicon Dioxide; C032734:silicon nitride