Strategic Material Design for Highly Reliable QLC 3D V-NAND Using Bypass Resistive Random Access Memory

Area of Science:

• Materials Science
• Electrical Engineering
• Solid-State Physics

Background:

• Conventional flash memory faces limitations, prompting research into alternatives like electrochemical random-access memory (ECRAM).
• Bypass RRAM shows promise for V-NAND applications due to its ion hopping conduction, but parameters for multilevel cell (MLC) operation are not fully understood.

Purpose of the Study:

• To establish design guidelines for bypass RRAM enabling highly uniform quadruple-level cell (QLC) operation.
• To explore the impact of quantized oxygen vacancy (V_o) injections on memory characteristics.

Main Methods:

• Material engineering was employed to precisely control ion migration in bypass RRAM.
• The study utilized the unique electrical properties of the WO resistive switching (RS) layer to minimize V_o migration.
• MATLAB simulations and experimental results were used to identify key parameters like ionic barrier (E_a,ion) and ion diffusivity (D_ion).

Main Results:

• Achieved low-voltage operation (<5 V) and a high on/off ratio (>10⁶) with minimal stoichiometry change (Δx < 0.08).
• Optimized parameters resulted in superior QLC performance with highly uniform distribution (σ/μ ∼ 0.01) and sensing margin (ΔG ∼ 4 μS).
• Demonstrated the absence of read disturbance issues in the optimized bypass RRAM.

Conclusions:

• The developed design guidelines facilitate highly uniform QLC operation in bypass RRAM for V-NAND memory.
• Reduced V_o migration at the nanoscale suggests potential for extending beyond QLC levels with quantized V_o injection.
• This research provides a pathway for highly uniform switching in next-generation V-NAND memory technologies.