Si Nanocrystal Memory Cell with Room-Temperature Single Electron Effects

A metal oxide semiconductor (MOS) memory based on Si nanocrystals has been fabricated. We have developed a repeatable process for forming uniform, small and high-density Si nanocrystals by low pressure chemical vapor deposition (LPCVD). Spherical nanocrystals with a 4.5 nm average diameter and a density of 5×1011/cm2 were obtained. A single transistor memory-cell structure, with a change in threshold voltage of about 0.48 V, corresponding to single electron storage in individual nanocrystals and having the capability of long-term charge storage is fabricated and characterized. For the first time, the single electron effect at room temperature, which shows a saturation of threshold voltage in a range of gate voltages with a periodicity of ΔVGS≈1.7 V, corresponding to single and multiple electron storage is reported. These finding prove the feasibility of a practical nanocrystal memory with potential for significantly high density, low power, and fast reading properties.