Operation of nanocrystalline-silicon-based few-electron memory devices in the light of electron storage, ejection, and lifetime characteristics

Abstract

A metal-oxide-semiconductor field-effect transistor memory device using nanocrystalline Si (nc-Si) dots as a floating gate over a short and narrow channel has been fabricated. Its operation at 77 K presents experimental evidence of storing and ejection of electrons associated with the nc-Si dot in the active area of the device. Though the lifetime of a single electron is apparently longer than the case when it is associated with another electron in the same nc-Si dot, a distribution in lifetime has been generally observed for the stored electrons in the nc-Si dots with the present memory devices.

Device Simulations in Coupled Floating-Gate Memories

“…5. In the case of the nano sized FG, [3][4][5][6][7][8][9][10] besides the CB effects, many nano sized FGs create more complicated electric fields and facilitate longer retention times. The limitation of the applicability of this calculation appears when the energy levels in the FGs become discrete.…”

“…In the first series, the quantum dots (QDs) are used for the FGs [3][4][5][6][7][8][9][10] where the Coulomb blockade (CB) effect of an electron is expected. Because double occupancy of electrons in a QD is energetically unfavorable, the write/ erase characteristics of the device are sensitive to the small number of electrons distributed in the QDs.…”

“…Although there are many new candidates for future memories, 1,2) here we focus on nano sized floating-gate (FG) memories, which would be able to be classified into two series. In the first series, the quantum dots (QDs) are used for the FGs [3][4][5][6][7][8][9][10] where the Coulomb blockade (CB) effect of an electron is expected. Because double occupancy of electrons in a QD is energetically unfavorable, the write/ erase characteristics of the device are sensitive to the small number of electrons distributed in the QDs.…”

A new channel percolation model for V/sub T/ shift in discrete-trap memories

“…(5). thus cannot account for the single-electron effects in DTM chargeloss characteristics [IS,16,19,201. Fig. 14 shows the calculated time evolution of AVT, for the same nanocrystal parameters of Fig.…”