A global modeling approach of the leakage phenomena in dielectrics

Jérémy Postel-Pellerin,Gilles Micolau,Maminirina Joelson,Philippe Chiquet,Jean-Baptiste Decitre

doi:10.1051/e3sconf/20198805002

Abstract

Thanks to its low noise level, the LSBB environment provides particular environment to carry out high quality electrical characterizations. In this paper, we propose a complete modeling approach of the experimental results from our experimental microelectronic setup. The tested device is a Metal Oxide Semiconductor (MOS) floating gate capacitor which can be found in electrostatic non volatile memories such as Flash. The main idea is to characterize and model the leakage current through the tunnel oxide. We proposed, in a previous work, a model for charge loss considering a fractional Poisson process, involving only two parameters, expressed as a Mittag-Leffler (ML) function. Here, we also propose a combo of Fowler-Nordheim (FN) and Poole-Frenkel (PF) models for leakage currents, based on tunnel effect transport through the oxide. It gives the leakage current on a medium-to-long scale of time while the ML model can possibly take into account a shorter time step. The perspective is to find a relationship between these different models, used in various fields, to propose a generic model of phenomena involving leakage in complex and porous materials at different scales of time and space.

Highlights

Flash memory cells are based on the floating gate technology principle [1]
The most widespread solution to enable semiconductor memories to be non-volatile, that is to say able to keep information without any power supply, is to use Metal Oxide Semiconductor (MOS) transistors whose threshold voltage is shifted by a charge stored in an isolated gate above the channel
Floating gate technologies consist in adding a second gate between the gate and the channel of a classical MOS transistor

Summary

Introduction

The most widespread solution to enable semiconductor memories to be non-volatile, that is to say able to keep information without any power supply, is to use MOS transistors whose threshold voltage is shifted by a charge stored in an isolated gate above the channel. Floating gate technologies consist in adding a second gate between the gate and the channel of a classical MOS transistor. This second gate, called "Floating Gate" (FG), can isolate charges to make the transistor threshold voltage variable. Barrier transparency in the tunnel oxide, which can be electrically modeled by a current source I, allows the injection of charges in the floating gate, shifting the MOS transistor threshold voltage VT according to equation (1): VT. A better understanding of these leakage currents is crucial to improve the whole quality of our memory cells, that’s why we have to develop powerful methods to reach very low current levels

Floating Gate Technique

Tunneling currents

Trap-assisted mechanisms

Classical Poisson process

Fractional Poisson process

Comparison between models and experiments