Electron energy distribution in Si/TiN and Si/Ru hybrid floating gates with hafnium oxide based insulators for charge trapping memory devices
| Autor: | Andre Stesmans, Florin Cerbu, Michel Houssa, Judit Lisoni, Valeri Afanas'ev, D. Andreev, Laurent Breuil |
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| Rok vydání: | 2016 |
| Předmět: |
Materials science
Oxide chemistry.chemical_element NAND gate Nanotechnology 02 engineering and technology Trapping Electron 01 natural sciences Molecular physics chemistry.chemical_compound 0103 physical sciences Materials Chemistry Energy level Work function Electrical and Electronic Engineering High-κ dielectric 010302 applied physics Surfaces and Interfaces 021001 nanoscience & nanotechnology Condensed Matter Physics Surfaces Coatings and Films Electronic Optical and Magnetic Materials chemistry 0210 nano-technology Tin |
| Zdroj: | physica status solidi (a). 213:265-269 |
| ISSN: | 1862-6300 |
| Popis: | Scaling the planar NAND flash cells to the 20 nm node and beyond mandates introduction of inter-gate insulators with high dielectric constant (κ). However, because these insulators provide a smaller electron barrier at the interface with the poly-Si floating gate, the program window and the retention properties of these scaled cells are jeopardized. To reduce the charge loss from the floating to the control gate, one may consider the introduction of a hybrid floating gate (HFG) structure comprised of poly-Si and a high work function (WF) metal, e.g., TiNx (x ∼ 1; WF ∼ 4.7 eV) or Ru (WF ∼ 5.3 eV). However, the very HFG concept is based on the assumption that electron trapping occurs inside the HFG stack rather than on traps present in the high-κ insulator. To examine this critical hypothesis, we analyzed the energy distribution of electrons trapped in flash cells with poly-Si(2 nm)/TiN (6 nm)/Hf0.8Al0.2Ox(19 nm, κ ∼ 15–19)/TiNx (10 nm) and Si(2 nm)/Ru (1 nm)/Hf0.8Al0.2Ox(5 nm)/Al2O3 (5 nm)/Hf0.8Al0.2Ox (5 nm)/TiNx (10 nm) trapping gate stacks using the exhaustive photo-depopulation spectroscopy. We found that trapped electron energy levels show a broad distribution (± 0.3 eV) centred at ∼3.2 eV below the oxide conduction band. The energy onset of electron de-trapping at ∼2.8 eV matches the TiNx/HfO2 barrier height found from internal photoemission experiments, indicating that electrons are predominantly trapped inside the HFG. |
| Databáze: | OpenAIRE |
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