Elimination of high transient currents and electrode damage during electroformation of TiO₂-based resistive switching devices

Abstract

Transient currents associated with electroforming TiO2-based resistive switching devices were measured using three distinct circuits designed to limit them, and they were correlated with physical changes in the top electrode using scanning electron microscopy. A transient current more than 10 times greater than expected was observed when only using the source meter to limit the current via the compliance set point. The large excursion arose from equipment delays and resulted in significant physical changes to the top electrode. An external resistor was used to decrease the excess transient current value to nearly zero, as long as parasitic capacitive discharges were also suppressed. Simultaneously, the physical changes to the top electrode were completely suppressed, indicating physical damage was related to Joule heating from the excess forming currents. The switching characteristics of all devices were similar, implying damage during electroformation of functional switches can be avoided by device/circuit design.

In Situ TEM Imaging of Defect Dynamics under Electrical Bias in Resistive Switching Rutile-TiO2

“…Since the current and voltage are similar in Figures 2d and 2e, the associated power dissipation is also comparable. However, the parasitic capacitance discharge of the cables could cause a current spike, especially for the higher voltage case in the single electroforming event (Lu et al, 2012). This current runaway event would be too fast (<1 ms) to be detectable in the I–V data, but could account for the structural transformations observed in Figure 2c.…”

“…This electroforming event is widely considered to create and or distribute defects necessary to accommodate resistive switching in the device (Akihiro, 2008). However, current runaway and excessive Joule heating commonly occurs during electroforming (Lu et al, 2012). Hence, it can be anticipated that appreciable heating may occur during electrical biasing and could cause reduction (oxygen vacancy formation).…”

Stable Metallic Enrichment in Conductive Filaments in TaOx‐Based Resistive Switches Arising from Competing Diffusive Fluxes

“…The circuit used for formation and switching is shown in Figure a with forming I–V in panel (b). The small lateral size (150 × 150 nm 2 ) limited the device's self‐capacitance and the on‐chip load resistor (58 kΩ) reduced current spikes due to the discharge of parasitic capacitances . The devices were formed using a triangular source voltage sweep with the positive voltage applied to the top electrode (unless otherwise noted).…”

Research Update: Electron beam-based metrology after CMOS

“…55,56 The large voltages and high speeds of these processes are well documented to produce capacitive current overshoots, which can lead to dramatic device damage. 57,58 This problem is typically solved in integrated CMOS systems, 51,59,60 but is challenging to observe within the limited bandwidth of a conventional TEM or SEM system. 61 This issue persists even after forming, since the most useful classes of devices are known to operate over orders of magnitude in time scales down to sub-nanosecond switching speeds.…”