Initialization process of Cu-based WO x conductive bridge RAM investigated via in situ transmission electron microscopy

Abstract

The initialization process of the Cu-WOX CBRAM was analyzed via in situ transmission electron microscopy (TEM). For the measurements, lateral-type devices were used to allow for clear microscopic observation. A widening of the electrode-gap by electrochemical dissolution of the Cu anode during voltage application was experimentally confirmed. These results provide evidence for the chemical reaction occurring at the anode side of the CBRAM. The resistance gradually decreased after multiple voltage sweep applications, and deposits appeared and grew in the electrode-gap region. Subsequently, sharp switching occurred, however, clear conductive filaments bridging the two electrodes were not detected within the resolution limit of the in situ TEM. Finally, a series of bipolar operations were realized; with continued bipolar operation, Cu accumulated in the switching region and device degradation occurred.