title: Single layer of Ge quantum dots in HfO2for floating gate memory capacitors.
abstract: High performance trilayer memory capacitors with a floating gate of a single layer of Ge quantum dots (QDs) in HfO2were fabricated using magnetron sputtering followed by rapid thermal annealing (RTA). The layer sequence of the capacitors is gate HfO2/floating gate of single layer of Ge QDs in HfO2/tunnel HfO2/p-Si wafers. Both Ge and HfO2are nanostructured by RTA at moderate temperatures of 600-700 °C. By nanostructuring at 600 °C, the formation of a single layer of well separated Ge QDs with diameters of 2-3 nm at a density of 4-5 × 1015m-2is achieved in the floating gate (intermediate layer). The Ge QDs inside the intermediate layer are arranged in a single layer and are separated from each other by HfO2nanocrystals (NCs) about 8 nm in diameter with a tetragonal/orthorhombic structure. The Ge QDs in the single layer are located at the crossing of the HfO2NCs boundaries. In the intermediate layer, besides Ge QDs, a part of the Ge atoms is segregated by RTA at the HfO2NCs boundaries, while another part of the Ge atoms is present inside the HfO2lattice stabilizing the tetragonal/orthorhombic structure. The fabricated capacitors show a memory window of 3.8 ± 0.5 V and a capacitance-time characteristic with 14% capacitance decay in the first 3000-4000 s followed by a very slow capacitance decrease extrapolated to 50% after 10 years. This high performance is mainly due to the floating gate of a single layer of well separated Ge QDs in HfO2, distanced from the Si substrate by the tunnel oxide layer with a precise thickness.
authors.affiliation: National Institute of Materials Physics, 405A Atomistilor Street, 077125 Magurele, Romania.
authors.forename: A M
authors.initials: AM
authors.lastname: Lepadatu
authors.forename: C
authors.initials: C
authors.lastname: Palade
authors.forename: A
authors.initials: A
authors.lastname: Slav
authors.forename: A V
authors.initials: AV
authors.lastname: Maraloiu
authors.forename: S
authors.initials: S
authors.lastname: Lazanu
authors.forename: T
authors.initials: T
authors.lastname: Stoica
authors.forename: C
authors.initials: C
authors.lastname: Logofatu
authors.forename: V S
authors.initials: VS
authors.lastname: Teodorescu
authors.forename: M L
authors.initials: ML
authors.lastname: Ciurea