 Paper presented at the 11th International School on Vacuum, Electron and Ion Technologies, 20}25 September 1999, Varna, Bulgaria. * Corresponding author. Tel.: #359-2-7144-448; fax: #359-2-975-36-32. E-mail address: elenada@issp.bas.bg (T. Dimitrova). Vacuum 58 (2000) 470}477 Leakage currents and conduction mechanisms of Ta  O  layers on Si obtained by RF sputtering  A. Paskaleva, E. Atanassova, T. Dimitrova* Institute of Solid State Physics, Bulgarian Academy of Sciences, Tzarigradsko Chaussee 72, Soxa 1784, Bulgaria Abstract The leakage current and the conduction mechanisms in Ta  O  layers on silicon with thickness in the range of 20}80 nm, obtained by reactive sputtering of Ta in an Ar/O  mixture have been investigated. Some dielectric and electrical properties, important for the application of the layers as storage capacitors in high-density dynamic random access memories (DRAM) and as a gate dielectric in metal oxide silicon transistors (MOSTs) are also considered. The results show that for as-deposited layers the leakage currents are higher for samples obtained at higher deposition temperature. The e!ect of postdeposition oxygen annealing depends on the thickness of Ta  O  layers. For thicker layers (40 nm), the leakage current after annealing increases and the e!ect is stronger for layers deposited at T  "493 K. It has been established that for thinner oxides (25 nm) the annealing strongly improves the leakage currents (the density of leakage current is 10 A/cm at applied "elds of about 1 MV/cm, which is low enough to satisfy the demands of 64 and 256 Mbit DRAM). For as-deposited samples the conduction mechanism is Poole Frenkel. After annealing depending on the "eld strength, di!erent types of conduction mechanisms occur: for electric "elds in the range 0.8}1.3 MV/cm, the conduction mechanism is dominated by electrode limited Schottky emission and for higher "elds ('1.5 MV/cm) it is bulk limited Poole Frenkel emission. The results are discussed in terms of bulk traps in the initial Ta  O  and their modi"cation after oxygen annealing.  2000 Elsevier Science Ltd. All rights reserved. Keywords: High dielectric constant thin "lms; Tantalum pentoxide; Electrical characterization; Leakage current; Conduction mechanisms 0042-207X/00/$ - see front matter  2000 Elsevier Science Ltd. All rights reserved. PII: S 0 0 4 2 - 2 0 7 X ( 0 0 ) 0 0 2 0 7 - 4