Silicon-based single-electron memory using a multiple-tunnel junction fabricated by electron-beam direct writing

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Abstract
Multiple-tunnel-junction-based nonvolatile single-electron-memory devices are promising for fast write/erase operation and long retention time. Fabrication of multiple-tunnel junctions with a predetermined number of barriers and islands is a major problem in realizing such devices. We have fabricated multiple-tunnel-junction-based single-electron devices by an electron-beam direct writing technique in a silicon-on-insulator layer. Using this technique, it is possible to fabricate multiple ultrasmall islands and tunnel barriers at a predetermined position, which is very important for reproducible device characteristics. Single-electron-memory devices based on multiple-tunnel junctions are fabricated. In these devices, a multiple-tunnel junction connects the gate electrode and a storage island. The Coulomb blockade across the multiple-tunnel junction acts as an energy barrier. Single-electron-memory operation is observed at 20 K. Retention time of at least 4 h has been observed.