Berlin 2005 – scientific programme

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SYFS: Nichtflüchtige Festkörperspeicher

SYFS 1: Overview, phase change and nanocrystal memories

SYFS 1.2: Talk

Saturday, March 5, 2005, 14:30–14:45, TU HE101

Fabrication of Si nanocrystals for memory application by ion irradiation through SiO₂/Si-interfaces — •B. Schmidt¹, K.-H. Heinig¹, L. Röntzsch¹, A. Mücklich¹, K.-H. Stegemann², E. Votintseva², and M. Klimenkov³ — ¹Research Center Rossendorf, Dresden — ²ZMD AG, Dresden — ³Research Center Jülich, Jülich

This contribution addresses self-assembling of Si-nanocrystals (NCs) in gate oxides, with special emphasis on size and position tailoring and their application as discrete charge storage centers in nanocrystal memories. The Si NCs for these multi-dot floating-gate memories have been produced by ion irradiation through SiO₂/Si-interfaces. Si excess within SiO₂ is formed by ion beam mixing of Si from the Si substrate and from the poly-Si capping layer into the gate oxide. Ion irradiation with 3x10¹⁵−1x10¹⁶ Si⁺ cm⁻² at 50-100 keV through 50 nm poly-Si and 15 nm SiO₂ on (001)Si results in a considerable Si excess. At the upper and lower interfaces of the gate oxide, this ion irradiation forms a metastable SiO_x composition. Si NCs are formed by phase separation into Si and SiO₂ during post-irradiation thermal treatment. Adjacent to the recovering interfaces, narrow SiO₂ zones becomes denuded of excess Si. More distant excess Si precipitates as Si NCs in the gate oxide. This approach was applied to nMOSFET-NC-memory fabrication in the standard CMOS line at ZMD. MOSFET characteristics in terms of write/erase voltage, duration of the programming time, endurance and retention have been evaluated.