Effect of yttrium feeding time on the electrical and structural properties of atomic layer deposited Y-doped TiO2 films for dynamic random-access memory capacitors

초록

This study systematically investigates the impact of yttrium (Y) and aluminum (Al) dopant concentrations and their distributions in rutile-structured TiO2 films grown via atomic layer deposition (ALD) for dynamic random-access memory capacitors. Excessive amounts of Y and Al dopants in the doping layer can induce localized Y2O3 and Al2O3 regions, which disrupt the crystallization of the TiO2 layer into a high-k rutile phase. To address this issue, subtle modulation of dopant concentrations is attempted by controlling the dopant feeding time in a single unit ALD cycle. This sub-one-cycle doping effectively prevents the localization of dopants, particularly for the Y dopant, enabling substitutional Y incorporation to efficiently decrease leakage current while minimizing a decrease in the dielectric constant of the TiO2 layer. An optimized yttrium-doped TiO2 capacitor was fabricated with a controlled dopant concentration and distribution, achieving a minimum equivalent oxide thickness of 0.50 nm and a physical oxide thickness of 8.4 nm while maintaining a leakage current density below 10-7 A cm-2.

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