Analysis of the Electrical ReRAM Device Degradation Induced by Thermal Cross‐Talk

Abstract

A switching of resistive memory cells leads to a local accumulation of Joules heat in the device. In resistive RAM (ReRAM) arrays, the heat generated in one cell spreads via common electrode metal lines to the neighboring cells and may cause their performance degradation. The performance degradation results in reduced number of switching cycles and, in extreme cases, even in a loss of a bit, caused by the rupture of the nanofilament. The authors propose a thermal analysis of the thermal cross‐talk, describe its impact on cells’ electric performance, and identify three major mechanisms for the ReRAM reliability: (i) thermal conductivity, (ii) the specific heat capacity, and (iii) geometry of the electrodes. Several ReRAM arrays are manufactured to vary thermal conductivity, specific heat and geometry of the electrodes by depositing eight different inert electrodes: Pt(50 nm)/Ti(30 nm), Ru(50 nm)/Ti(30 nm), Co(50 nm)/Ti(30 nm), Pt(50 nm/Cu(100 nm)/Ti(30 nm), Pt(50 nm)/ Cu(200 nm)/Ti(30 nm), Ru(50 nm/Cr(30 nm), Ru(50 nm)/Ti(50 nm), and Rh(50 nm)/Cr(30 nm). The experimentally found differences of the degradation of electric performance of the array cells performed under identical circumstances can be correctly predicted by the proposed thermal analysis using the material properties and geometry parameters of the electrodes.

Soret-Effect Induced Phase-Change in a Chromium Nitride Semiconductor Film

“…47 However, the matrix of the oxide layer in ReRAM is typically insulating, and the filament phase is often chemically and thermally unstable, leading to poor data retention properties. 48,49 In contrast, the CrN memory device in this study combines the benefits of phase change in PCRAM and the thermally induced atomic diffusion process in ReRAM, providing a promising approach to addressing the challenges of the high-energy-budget melting process in PCRAM and the poor thermal stability of ReRAM simultaneously.…”

Inertness and Other Properties of Thin Ruthenium Electrodes in ReRAM Applications

“…The local temperature at the thinnest part of the filament can reach temperature in excess of 1084°C [37]. 1084°C is the melting temperature of Cu (see Table 1) and melting of Cu electrodes has been experimentally observed after excessive heating of a ReRAM cell [38]. At such high temperature, the Cu atoms of the Cu CF diffuse out, may undergo the redox reaction in TaO x , and are returned as Cu + ions by the electric drift fields back to the Cu electrode or stay immobilized in TaO x material.…”

Thermal Reliability Issues in ReRAM Memory Arrays

“…In Ref. [30], it has been experimentally observed that frequent switching of a ReRAM cell leads to the incipient melting of the Cu electrodes including Cu pads. This gives a definite reference point for the local temperature of 1085°C, which is the melting temperature of copper.…”

“…To make practical use of Eq. ( 5), we avail ourselves of a valuable experimental reference [30] that can be used to calibrate Eq. ( 5).…”

“…( 5). When a cell is repeatedly switched on and off under specific switching conditions for moderately large R on and low value for RR, which were purposefully designed to increase the amount of heating, we witness melting of the copper electrode at the heated device that extends to the metal line pads [30]. It has also been noticed that the contact pads for the Pt electrodes are free of any visible distortion of their square shape on account of much higher melting temperature of Pt (1768°C) than that of Cu (1085°C).…”