Phenomenological modelling of non-volatile memory threshold voltage shift induced by nonlinear ionization with a femtosecond laser

Abstract

The behaviour of semiconductor materials and devices subjected to femtosecond laser irradiation has been under scrutiny, for many reasons, during the last decade. In particular, recent works have shown that the specific functionality and/or geometry of semiconductor devices, among which non-volatile memory (NVM) devices hold a special place, could be used to improve the knowledge about ultrafast laser-semiconductor interactions. So far, such an approach has been applied to draw conclusions about the spatio-temporal properties of laser propagation in bulk materials. Here, by comparing the evolution of the electrical characteristics of Flash cells under the cumulative effect of repeated femtosecond laser pulses with first-order physical considerations and TCAD (Technology Computer Aided Design) simulations, we clearly establish the role of the carriers created by nonlinear ionization on the functionality of the structures. The complete electrical analysis informs indirectly on the energy of the laser-produced free-carriers which, to date, was almost inaccessible by an experimental method applicable to the bulk of a material. Establishing the link between the carrier energy and laser parameters is of major importance to improve the comprehension of the nonlinear ionization mechanisms associated to intense laser-semiconductor interactions and applied in various fields from microelectronics to laser micromachining.

In‐Volume Laser Direct Writing of Silicon—Challenges and Opportunities

“…The later technological developments of femtosecond lasers as well as near‐infrared lasers enabled to irradiate the device from the silicon substrate (i.e., the backside) by two‐photon absorption—and, consequently, to generate free carriers with a remarkable spatial resolution. [ 119–134 ] The plasma production close to the logic gates of the irradiated device implies that some of the free carriers are able to migrate through a tunnel oxide so that the logic state of the microelectronic component (e.g., flash memory, photodiode) is modified in a stable manner after irradiation.…”

Preparation of Cobalt Nanoparticles

“…Capacitance–voltage (C–V) electrical measurements were conducted on the fabricated device, and a clear hysteresis in the C–V curve was observed due to the charging effect in the Co NPs. Thus, laser irradiation is one of the most efficient processes for formation or insertion of metal NPs into gate oxides, which is relevant for the development of non‐volatile memory devices [190,191] …”