Origin and repartition of the oxide fixed charges generated by electrical stress in memory tunnel oxide

Abstract

A method is proposed to determine the origin and the spatial oxide fixed charge repartition in memory tunnel oxide from Fowler–Nordheim current measurements after electrical stress. The Poisson equation resolution in the dielectric layer is required to account for the nonsymmetric tunneling barrier deformation, resulting from charges generated within the dielectric layer. From current–voltage characteristics measurements and simulations, we have determined the spatial distribution of the oxide fixed charges within the dielectric layer of metal/SiO2/metal structures. In addition, the kinetics of the oxide charge generation can be explained by a dispersive hydrogen transport model.

Investigation of the effects of constant voltage stress on thin SiO2 layers using dynamic measurement protocols

“…The source of this positive charge could be the migration under the oxide field of some of the holes trapped in the oxide during the CVS from the gate to the back gate. After the current peak is reached, negative charging of the oxide becomes prevalent and the decrease of the tunneling current can be naturally explained [12].…”

Effect of fixed dielectric charges on tunnelling transparency in MIM and MIS structures

“…Thus, from positive and negative current-voltage measurements, we are able to find the fixed charge distribution if we consider that the charge close to the substrate (or the gate) degrades, principally, the transparency of substrate (or gate) electrons. This method has been successfully tested on MOS capacitors grown on N þ substrate with an SiO 2 tunneling layer of 8.3 nm and an N doped polysilicon gate [12].…”