Operando observation of resistive switching in a resistive random-access memory by laser-excited photoemission electron microscope

Abstract

We developed a laser-excited photoemission electron microscope (Laser-PEEM) that enables us to perform a non-destructive operando observation for elucidating the changes in the physical properties of electronic devices. By utilizing the Laser-PEEM, the non-volatile resistance change in the resistive random-access memory (ReRAM) was clearly visualized, even though the resistance change occurred under the electrode of the ReRAM, thanks to the deep probing depth. The operando observation of the Laser-PEEM is very promising as an observation method for various kinds of devices because the observation simultaneously provides us with morphological and electrical properties in real time.

Visualizing the Local Composition Changes during Resistive Switching in Planar TaOx-ReRAMs

“…9−16 This has led to numerous high-resolution investigations of the conductive filaments using scanning probe microscopy (SPM), 17−19 transmission electron microscopy (TEM), 20−23 and photo electron emission microscopy. 24,25 As a result, different resistive switching mechanisms in TaO x -ReRAMs have been proposed in the literature. While some studies attributed the resistance changes to the migration of oxygen vacancies [5][6][7]16,26 and the alternation of composition from TaO 2 to Ta 2 O 5 in the filaments, 27−30 others reported the migration of tantalum and oxygen atoms during resistance switches, using scanning tunneling microscopy (STM) measurements.…”

“…The formation of conductive filaments in TaO x -ReRAM devices plays a fundamental role in defining their functionality. Recently, long-term and robust retentions have been demonstrated in TaO x -ReRAMs, which were attributed to the stability of the conductive filaments. − Moreover, depending on the conditions of these filaments, analog resistive switching has been reported in TaO x -ReRAMs. − This has led to numerous high-resolution investigations of the conductive filaments using scanning probe microscopy (SPM), − transmission electron microscopy (TEM), − and photo electron emission microscopy. , As a result, different resistive switching mechanisms in TaO x -ReRAMs have been proposed in the literature. While some studies attributed the resistance changes to the migration of oxygen vacancies − ,, and the alternation of composition from TaO 2 to Ta 2 O 5 in the filaments, − others reported the migration of tantalum and oxygen atoms during resistance switches, using scanning tunneling microscopy (STM) measurements .…”

Dielectric breakdown behavior of ferroelectric HfO2 capacitors by constant voltage stress studied by in situ laser-based photoemission electron microscopy

“…14) Because of the low photon energy, the probing depth is large enough to detect photoelectrons near the Fermi level (E F ) at depths of 40 nm or more, as shown in Ref. 15. Furthermore, through the in situ laser-PEEM observation, the filament formation was visualized through the top electrode.…”

“…Furthermore, through the in situ laser-PEEM observation, the filament formation was visualized through the top electrode. 15,16) The in situ laser-PEEM is an effective tool for visualizing leakage paths inside capacitors without any destructive sample treatments.…”

“…We used the in situ laser-PEEM system, an in situ voltage application, and a characterization system with a source measure unit, which is described elsewhere. 15) A CW laser with a photon energy of 4.66 eV is used as an excitation light. The force and ground of the source measure unit are connected to the top electrode and bottom electrode, respectively.…”