Characterization of Multistep Electron Charging and Discharging of a Silicon Quantum Dots Floating Gate by Applying Pulsed Gate Biases

Abstract

Electron charging and discharging operations for a silicon quantum dots (Si-QDs) floating gate with discrete charged states were characterized in n-metal–oxide–semiconductor field-effect-transistors (MOSFETs) by applying single-pulsed gate biases Vg with pulse widths ranging from 10 ns to 100 ms. The drain current levels for charged states increase stepwise with Vg pulse width, which indicates multistep electron charging in the Si-QDs floating gate due to quantization energy and electron charging. The gate voltages required to minimize the time for charging and discharging the Si-QDs floating gate are limited by the leakage current through the control oxide, which partially compensates the charging or discharging current through the tunnel oxide in the high-gate-voltage region. The transient variation of the drain current at zero gate bias, after the application of pulsed gate biases for the dot floating gate to be charged, shows that a critical transition from an unstable charged state to a stable one occurs, depending on the pulse height or width. This suggests the redistribution of electrons in the floating gate during the metastable state, which involves a reduction in the effective charging energy and the resultant elimination of the Coulomb blockade.

Formation of High-Density Pt Nanodots on SiO2 Induced by Millisecond Rapid Thermal Annealing Using Thermal Plasma Jet for Floating Gate Memory

“…In metal-oxidesemiconductor field-effect transistor (MOSFET) applications, Si nanocrystals embedded in a SiO 2 matrix are used as charge storage nodes in floating gate memory devices. [1][2][3][4][5][6][7] From the viewpoint of charge storage capacity, metallic nanodots (NDs) with an appropriate work function for generating a deep potential well are promising candidates for charge storage nodes. So far, metallic-NDs formed at temperatures higher than 400 C have been applied to a floating gate in nonvolatile memories.…”

Light-Induced Carrier Transfer in NiSi-Nanodots/Si-Quantum-Dots Hybrid Floating Gate in Metal–Oxide–Semiconductor Structures

“…The application of Si quantum dots (Si-QDs) and metallic nanodots (NDs) in the floating gate (FG) of metal-oxidesemiconductor (MOS) structures has recently attracted much attention because of their unique physical properties, which lead us to develop novel functional memories. [1][2][3][4][5][6][7] The discrete charged states of Si-QDs due to the quantum confinement effect and charging energy play a role in the multistep charging of the Si-QDs FG. Thus far, we have demonstrated a unique multistep threshold voltage shift in nMOSFETs with a Si-QDs floating gate at room temperature due to the electron charging and discharging of Si-QDs with discrete charged states.…”

“…Thus far, we have demonstrated a unique multistep threshold voltage shift in nMOSFETs with a Si-QDs floating gate at room temperature due to the electron charging and discharging of Si-QDs with discrete charged states. [2][3][4] On the other hand, metallic NDs with a large work function show stable charge storage characteristics. 5,6) Recently, we have demonstrated stable storage of many electrons and multistep electron injection in MOS capacitors with a hybrid FG consisting of Si-QDs and NiSi-NDs.…”

Large-Scale First-Principles Electronic Structure Calculations for Nano-Meter Size Si Quantum Dots

“…Silicon quantum dots (QDs) have been attracted much attention because of the potential for several device applications, such as multi-valued memories [1], single-electron transistors [2], and optical emitting devices [3].…”