Rutile Without Substrate Limitations: Top‐Interface‐Driven Crystallization of TiO ₂

Abstract

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 2 offers a dielectric constant significantly higher than that of tetragonal ZrO 2 and anatase TiO 2 . 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 2 upper layer stabilizes rutile TiO 2 at 400°C regardless of the crystallinity of the underlying ZrO 2 /TiN stack. Thickness‐dependent phase maps reveal an interfacial‐energy‐driven anatase‐to‐rutile transition for thin amorphous TiO 2 layers, enabling rutile formation even on amorphous ZrO 2 . The resulting TiO 2 /ZrO 2 /TiN capacitors exhibit a dielectric constant of approximately 80 and a reduced equivalent oxide thickness, comparable to that of ZrO 2 ‐based stacks. A methanol‐assisted reduction‐etching process allows selective removal of RuO 2 by O 3 with minimal TiN oxidation. This top‐interface engineering concept offers a substrate‐agnostic approach to rutile TiO 2 that is compatible with DRAM process windows and can be extended to other polymorphic oxides.