Optimization of Zr concentration in HZO-based charge trap layers for enhanced flash memory performance

초록

This study investigates the effect of Zr concentration in HZO thin films for application as charge trap layers (CTL) in charge trap flash (CTF) memory devices. Non-ferroelectric HZO thin films with various Zr concentrations are deposited using atomic layer deposition, and their material and electrical properties are analyzed. Increasing Zr concentration narrows the bandgap and increases oxygen vacancies. The low-frequency noise and dielectric breakdown measurements reveal that higher Zr concentrations result in increased trap density but a reduced breakdown electric field. This indicates a trade-off between improved charge storage capability and the reliability of HZO in CTL applications. Subsequently, CTF devices incorporating HZO-based CTLs are fabricated to evaluate memory performance. The device with 10% Zr achieves the widest memory window (1.96 V), excellent endurance over 106 program/erase cycles (5.35 % memory window reduction rate), and retention after 106 s (15.9 % memory window reduction rate). In contrast, the device with 20% Zr exhibits degraded erase efficiency due to excessive trap density, resulting in a reduced memory window. These results demonstrate that a Zr concentration of 10% in HZO-based CTL is the optimized composition for flash memory performance, delivering superior memory window, endurance, and retention characteristics essential for reliable CTF memory. Copyright © 2025. Published by Elsevier B.V.

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