Materials Characterization and Electrical Performance of Bilayer Structures for Enhanced Electrodeposition in Programmable Metallization Cells

Long channel lateral programmable metallization cell (PMC) devices, in which a metal electrodeposit is formed on a solid electrolyte between two coplanar electrodes several microns apart, have a variety of applications beyond standard microelectronics. Whereas fast electrodeposit growth over considerable distances can be achieved using high ion mobility chalcogenide electrolytes, the use of more foundry-friendly materials, including copper-doped transition metal oxides, leads to extremely low electrodeposit growth rates due to their low ion mobility and high resistivity. In this paper, a material system comprising a Cu₂O/Cu-WO₃ bilayer formed by low temperature oxidation of Cu on WO₃ is examined. The Cu₂O overlayer provides a low resistance parallel path for electrons, allowing electrodeposition to occur along the entire length of the device, thereby increasing the rate at which the electrodeposit fills the channel. A study of devices prepared under different conditions, resulting in different copper oxide thicknesses and copper concentrations in the layers, shows the influence of processing conditions on material composition, activation energy for current transport, electrodeposit morphology, and electrical characteristics. It is demonstrated that a very wide range of operating conditions is possible, including the bridging of 14 μm long channels in under 3 s using 2 V bias.