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Capacitor structures utilized in modern dynamic random access memory (DRAM) cells require the conformal growth of high-kfilms on electrode materials. In this context, the atomic layer deposition (ALD) of rutile-phase TiO2on nearly lattice-matched substrates such as RuO2has been extensively explored. It is typically desired to grow such insulating films at high temperatures to ensure low defect concentrations and high crystallinity. However, with increasing growth temperature, it is also crucial to consider the aggravated effect of interface reactions that could potentially hinder final device performance. Here, we report the high-temperature ALD growth of TiO2on RuO2substrates using the heteroleptic precursor trimethoxy(pentamethylcyclopentadienyl)titanium ((CpMe5)Ti(OMe)3) and O3. High-quality, rutile-phase TiO2films with large dielectric constants of ∼100 could be grown at temperatures exceeding 300 °C. When the growth temperature reaches 330 °C, we find that an anomalous RuO2reduction reaction occurs due to interactions between the substrate and Ti precursor. The reduced Ru is transformed into volatile RuO4during the subsequent O3injection steps, resulting in partial etching of the substrate. Simple RuO2/TiO2/RuO2capacitor devices fabricated from optimized films demonstrate excellent dielectric performance with an equivalent oxide thickness (EOT) of 0.5 nm at leakage current densities of less than 10–7A/cm2. A further reduction of EOT to 0.4 nm could be achieved by implementing a single cycle of Al doping to the TiO2films, surpassing the benchmark values proposed for next-generation DRAM capacitors by a safe margin. Our findings clearly showcase the benefits of high-temperature ALD in the semiconductor technology, as well as providing guidelines for the interpretation of the convoluted interface reactions tied to its implementation.

In general, the electronic and optical properties of oxide films can significantly benefit from highly textured crystallinity. However, oxide films grown by atomic layer deposition (ALD), a powerful technique for the synthesis of high-quality, nanoscale thin films, usually exhibit amorphous or randomly oriented polycrystalline phases. Here, we demonstrate the growth of highly textured rutile phase ALD TiO2films through rational substrate design. Both a- and c-axis preferentially oriented TiO2films are obtained by varying the lattice parameters of the initial ALD growth surface. Under optimized conditions, we find that it is possible to deposit high-quality, c-axis preferentially aligned TiO2films with a bulk dielectric constant approaching 185, rivaling the single crystal limit. These films display a remarkably high dielectric constant of 117 despite thin thickness of 5.2 nm. Moreover, the addition of a single doping sequence of Al2O3successfully suppresses leakage currents to levels compatible with modern dynamic random access memory cells, all the while maintaining the high bulk dielectric constant of 137. These results clearly highlight the prospect of utilizing crystal orientation engineering in ALD thin films for emerging semiconductor devices.