Rutile Without Substrate Limitations: Top-Interface-Driven Crystallization of TiO<sub>2</sub>.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41954288.
- Also identified by DOI 10.1002/adma.73040 and PMC identifier 13155257.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Controlling the polymorphic phases within the thermal budget of atomic layer deposition (ALD) is essential for integrating high-k dielectrics into dynamic random-access memory (DRAM) capacitors. Rutile TiO<sub>2</sub> offers a dielectric constant significantly higher than that of tetragonal ZrO<sub>2</sub> and anatase TiO<sub>2</sub>. However, its application on industry-standard TiN electrodes is impeded by the lack of rutile-compatible lattice matching. A top-interface-driven stabilization strategy is demonstrated, where a structurally compatible RuO<sub>2</sub> upper layer stabilizes rutile TiO<sub>2</sub> at 400°C regardless of the crystallinity of the underlying ZrO<sub>2</sub>/TiN stack. Thickness-dependent phase maps reveal an interfacial-energy-driven anatase-to-rutile transition for thin amorphous TiO<sub>2</sub> layers, enabling rutile formation even on amorphous ZrO<sub>2</sub>. The resulting TiO<sub>2</sub>/ZrO<sub>2</sub>/TiN capacitors exhibit a dielectric constant of approximately 80 and a reduced equivalent oxide thickness, comparable to that of ZrO<sub>2</sub>-based stacks. A methanol-assisted reduction-etching process allows selective removal of RuO<sub>2</sub> by O<sub>3</sub> with minimal TiN oxidation. This top-interface engineering concept offers a substrate-agnostic approach to rutile TiO<sub>2</sub> that is compatible with DRAM process windows and can be extended to other polymorphic oxides.