Dependence of Electrons Loss Behavior on the Nitride Thickness and Temperature for Charge Trap Flash Memory Applications

Abstract

Charge Trap Flash (CTF) memory devices, otherwise known as metal-oxide-nitride-oxide-silicon structures, have been the subject of attention in the semiconductor industry due to their advantages over conventional floating gate type memory. These advantages include lower programming voltage, superior programming/erasing speeds, and a simple fabrication process compatible with standard complementary metal-oxidesemiconductor technology [1-3]. Recently, CTF memory devices have gained increasing interest in the three dimensional (3D) integration for next generation nonvolatile memory technology [4,5]. The tunnel oxide thickness plays a crucial role in regulating the erasing speed, data retention characteristics and charge loss mechanisms for CTF memory devices [6], while the thickness of the nitride charge trapping layer is less critical. Nevertheless, in 3D architectures, the nitride thickness has a direct effect on charge storage performance and array density [7]. Moreover, temperatures [8] and trap energy levels [9,10] also are considerable factors for understanding the electron loss mechanisms. Hence, in this letter, Pt/Al2O3/Si3N4/SiO2/Si (MANOS) charge trapping memory capacitors with various thicknesses of nitride layer were fabricated. We investigated and analyzed the effect of nitride thickness, trap energy levels and temperatures on electrons loss behavior in the retention state for MANOS capacitors. Also, a reasonable nitride thickness range was obtained through electrical characteristic measurements. Four charge loss mechanisms [11,12] are involved in the data retention state for scaled CTF memory devices: trapped electrons tunnel from traps to the silicon conduction band (T-B), trapped electrons Zhenjie Tang, Ma Dongwei, Zhang Jing, Jiang Yunhong, and Wang Guixia College of Physics and Electronic Engineering, Anyang Normal University, Anyang 455000, P.R.China