Role of IGZO thickness for oxygen reservoir control in stacked IGZO/ZrOx layers: Towards reliable, uniform performance of flexible random-access memories

• Published in: Journal of alloys and compounds Vol. 922; p. 166199
• Main Authors: Kumar, Ajit, Krishnaiah, Mokurala, Mishra, Dhananjay, Jo, Hyeonbin, Jin, Sung Hun
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 20.11.2022; Elsevier BV
• Subjects: Bend radius; Bilayer (IGZO/ZrOx); Biomedical materials; Crystal structure; Cycle ratio; Flexible RRAM; Indium gallium zinc oxide; Lattice vacancies; Oxygen ions; Oxygen reservoir; Photoelectrons; Physical properties; Polyethylene terephthalate; Random access memory; Reliability; Reservoirs; Substrates; Switching; Thickness; Vacancies; X ray photoelectron spectroscopy; Thickness; Oxygen reservoir; Flexible RRAM; Reliability; Bilayer (IGZO/ZrOx)
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2022.166199

For securing the enhanced properties in ZrOx based RRAMs, the roles of IGZO thickness in the switching window and stability of stacked IGZO/ZrOx RRAM devices are systematically investigated. The physical characteristics of the amorphous crystal structure of IGZO film and the variation of oxygen vacancy with IGZO thickness are validated by glancing angle X-ray diffraction (GAXRD) and X-ray photoelectron spectroscopy (XPS) analysis. The reliable and uniform switching properties for bilayer RRAMs with (92 ± 2) nm IGZO films are obtained as a stable switching up to 103 cycles, ROFF/RON ratio (~102), and retention for 104 s. The improvement in the RRAM performances is interpreted with oxygen vacancy in the IGZO layer, which facilitates the role of oxygen reservoir owing to its oxygen-deficient composition to absorb/discharge oxygen ions. With respect to the switching mechanism, set cycles are governed by a trap-mediated space-charge-limited current (SCLC) conduction. Furthermore, the optimal IGZO thickness-based bilayer IGZO/ZrOx RRAM device on a flexible polyethylene terephthalate (PET) substrate is demonstrated with stable switching up to 103 cycles, ROFF/RON ratio (>10), and retention for 104 s, along with the stable performance under different bending radii. With the scheme of IGZO based oxygen vacancy control, IGZO/ZrOx bilayer-based RRAM devices are expected to be one of viable options for the flexible, wearable, and biomedical applications. •IGZO/ZrOx bilayer-based RRAM devices were implemented on rigid and flexible substrates.•The role of oxygen vacancies in IGZO on resistive switching (RS) of bilayer-RRAM devices.•RRAM demonstrates RON/ROFF ≈ 102, good endurance (≈103 cycles), and retention over 104 s.•Flexible RRAM (FRRAM) exhibits good endurance (≈103 cycles) and retention over 104 s.•Stable RS characteristics under bending test confirm the mechanical flexibility of FRRAM.