RRAM characteristics using a new Cr/GdO_x/TiN structure

Resistive random access memory (RRAM) characteristics using a new Cr/GdO_x/TiN structure with different device sizes ranging from 0.4 × 0.4 to 8 × 8 μm² have been reported in this study. Polycrystalline GdO_x film with a thickness of 17 nm and a small via-hole size of 0.4 μm are observed by a transmission electron microscope (TEM) image. All elements and GdO_x film are confirmed by energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy analyses. Repeatable resistive switching characteristics at a current compliance (CC) of 300 μA and low operating voltage of ±4 V are observed. The switching mechanism is based on the oxygen vacancy filament formation/rupture through GdO_x grain boundaries under external bias. After measuring 50 RRAM devices randomly, the 8-μm devices exhibit superior resistive switching characteristics than those of the 0.4-μm devices owing to higher recombination rate of oxygen with remaining conducting filament in the GdO_x film as well as larger interface area, even with a thinner GdO_x film of 9 nm. The GdO_x film thickness dependence RRAM characteristics have been discussed also. Memory device shows repeatable 100 switching cycles, good device-to-device uniformity with a switching yield of approximately 80%, long read endurance of >10⁵ cycles, and good data retention of >3 × 10⁴ s at a CC of 300 μA.