Different charging behaviors between electrons and holes in Si nanocrystals embedded in SiN _x matrix by the influence of near-interface oxide traps

Abstract

Si-rich silicon nitride films are prepared by plasma-enhanced chemical vapor deposition method, followed by thermal annealing to form the Si nanocrystals (Si-NCs) embedded in SiN x floating gate MOS structures. The capacitance-voltage (C-V ), current-voltage (I-V ), and admittance-voltage (G-V ) measurements are used to investigate the charging characteristics. It is found that the maximum flat band voltage shift (∆V FB ) due to full charged holes (∼ 6.2 V) is much larger than that due to full charged electrons (∼ 1 V). The charging displacement current peaks of electrons and holes can be also observed by the I-V measurements, respectively. From the G-V measurements we find that the hole injection is influenced by the oxide hole traps which are located near the SiO 2 /Si-substrate interface. Combining the results of C-V and G-V measurements, we find that the hole charging of the Si-NCs occurs via a two-step tunneling mechanism. The evolution of G-V peak originated from oxide traps exhibits the process of hole injection into these defects and transferring to the Si-NCs.

Scaling dependence of memory windows and different carrier charging behaviors in Si nanocrystal nonvolatile memory devices*

“…Due to the compatibility with the standard CMOS technology, Si-NC NVM devices have been widely studied. [10][11][12][13][14][15][16] However, with the scaling down of the device structures, the number of Si-NCs in the floating gate of the device decreases gradually, resulting in the reduction of the stored charge quantity in the device. Therefore, what effect the reduction of stored charge quantity has on the memory window becomes the critical issue for the real application of Si-NC NVM devices.…”