Methods for Increasing the Efficiency of the Electroforming Process of Open Metal–Insulator–Metal Sandwich Structures

Abstract

The metal–insulator–metal sandwich structures with the end surface of the insulator film (insulating slit) open to the gas environment were manufactured using thin-film technology. Electroforming, which consists of applying voltage according to a specific algorithm, causes the formation of conductive phase particles due to the destruction of organic molecules adsorbed on the open surface of the insulator by electron impact during the electric current flow. The accumulation of particles leads to the growth of a linked conductive cluster (a conductive carbon medium) and the formation of a conductive nanostructure with the memristor properties in the insulating slit. The practical use of such structures is limited by the low efficiency of electroforming: relatively long process times (on the order of several seconds) and an increased probability of electrical breakdown of the structure. Several ways to improve the efficiency of the electroforming process are presented. Firstly, the use of the correct voltage polarity for the open TiN–SiO₂–W sandwich structure, where W should be the anode, which sharply reduces the probability of breakdown. Secondly, the use of two-stage electroforming: first, the formation of conductive channels in an “oil-free” vacuum after annealing in it, when the voltage can be applied in parallel to a large number of structures, and then in an “oil” vacuum containing organic molecules at significantly lower voltages and exposures. Thirdly, replacing the tungsten anode with a molybdenum one, which, while maintaining the advantages of tungsten, leads to an increase in the initial conductivity of the open sandwich structure (TiN–SiO₂–Mo) by several orders of magnitude, and, therefore, to an acceleration of the electroforming process and a decrease in the applied voltages.