Regulating the Resistive Switching Performance of CBRAM Devices by Controlling ALD Process Purge Time

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Conductive bridging random access memory (CBRAM) performance relies heavily on the controllable formation and rupture of conductive filaments (CFs) in the dielectric layer. This study independently regulates the purge times of trimethylaluminum (TMA) and deionized water (H2O) in atomic layer deposition (ALD) of Al2O3. By comparing three purge conditions (6;6 s, 6;2 s, 4;2 s), we show that purge time governs the density and spatial distribution of oxygen vacancies. X-ray photoelectron spectroscopy (XPS) analysis reveals that symmetric short purging (4;2 s) yields moderately dense and uniformly distributed vacancies, whereas an insufficient H2O purge (6;2 s) causes local vacancy clustering. Complementary DFT calculations show that the oxygen vacancy formation energy increases from 0.43 eV (Opoor) to 6.54 eV (Orich), explaining why residual H2O lowers the oxygen potential and promotes vacancy formation. Moreover, the divacancy formation energy of –0.3 eV (para configuration) confirms that vacancies tend to aggregate, supporting the observed clustering. The optimized 4;2-s device guides vertical Cu+migration to form slender, reversible CFs, achieving low forming voltage (~1.3 V), cycling endurance > 1200 cycles, and stable retention. This work demonstrates that ALD purge time engineering is an effective route to tailor defect states and enhance CBRAM performance.

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