In this study, we fabricated TiSi2 nanocrystal nonvolatile memory devices with silicon nitride–oxide–nitride (NON) and SiO2 tunnel barriers. The TiSi2 nanocrystals with diameters of 2–5 nm and a density of 1.5 ×1012 cm-2 were formed using radio frequency magnetron sputtering in argon and a postannealing process. The memory effect of the TiSi2 nanocrystal memory device with the NON tunnel barrier was observed at about 0.7 V at 100 ms when the applied program/erase voltages were +7 V/-7 V. Also, the memory window of the NON tunnel barrier device was maintained up to 1.3 V after 103 s. These results indicate that the NON tunnel barrier provides an effective tunneling thickness for the fast program/erase speeds and an adequate physical thickness for long charge retention characteristics in nonvolatile memory devices.

Self‐assembled SnO2 quantum dots were fabricated by a chemical process between a BPDA‐PDA polyamic acid and a Sn film. A nano‐floating gate capacitor having metal–insulator–semiconductor structure has been formed on p‐type Si substrate with SnO2 quantum dots and dielectric polymer layer. The size and density of fabricated SnO2 quantum dot were about 15 nm and 2.4 × 1011 cm–2, respectively. The electrical properties of the nano‐floating gate capacitor have been investigated by measuring capacitance–voltage characteristics. Then, the flat‐band voltage shift due to charging of the electron in SnO2 quantum dot was ranged from 1.2 V to 4 V. And the transmission electron microscopy and the optical absorption spectra have been measured to investigate the morphology and absorbance of the SnO2 quantum dots embedded in polyimide. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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We have fabricated the nano-floating gate memory with the TiSi2 and WSi2 nanocrystals embedded in the dielectrics. The TiSi2 and WSi2 nanocrystals were created by using sputtering and rapidly thermal annealing system, and then their morphologies were investigated by transmission electron microscopy. These nanocrystals have a spherical shape with an average diameter of 2-5 nm. The electrical properties of the nano-floating gate memory with TiSi2 and WSi2 nanocrystals were characterized by capacitance-voltage (C-V) hysteresis curve, memory speed and retention. The flat-band voltage shifts of the TiSi2 and WSi2 nanocrystals capacitors obtained appeared up to 4.23 V and 4.37 V, respectively. Their flat-band voltage shifts were maintained up to 1.6 V and 1 V after 1 hr.

A nano-floating gate capacitor with WSi2 nanocrystals embedded in SiO2 dielectrics was fabricated. The WSi2 nanocrystals were created from ultrathin WSi2 film during rapid thermal annealing process and their average size and density were about 2.5 nm and 3.59 x 10(12) cm(-2), respectively. The flat-band voltage shift due to the carrier charging effect of WSi2 nanocrystals were measured up to 5.9 V when the gate voltage sweep in the range of +/- 9 V. The memory window was decreased from 3.7 V to 1.9 V after 1 h and remained about 3.7 V after 10(5) programming/erasing cycles. These results show that there is a possibility for the WSi2 nanocrystals to be applied to nonvolatile memory devices.