Recent progress for obtaining the ferroelectric phase in hafnium oxide based films: impact of oxygen and zirconium

• Published in: Japanese Journal of Applied Physics Vol. 58; no. SL; p. SL0801
• Main Authors: Schroeder, Uwe, Materano, Monica, Mittmann, Terence, Lomenzo, Patrick D., Mikolajick, Thomas, Toriumi, Akira
• Format: Journal Article
• Language: English
• Published: Tokyo IOP Publishing 01-11-2019; Japanese Journal of Applied Physics
• Subjects: Crystallization; Deposition; Electrical properties; Electrode materials; Ferroelectric materials; Ferroelectricity; Grain size; Hafnium oxide; Orthorhombic phase; Oxygen; Structural analysis; Surface energy; Thin films; Zirconium
• ISSN: 0021-4922; 1347-4065
• DOI: 10.7567/1347-4065/ab45e3

Different causes for ferroelectric properties in hafnium oxide were discussed during the last decade including various dopants, stress, electrode materials, and surface energy from different grain sizes. Recently, the focus shifted to the impact of oxygen vacancies on the phase formation process. In this progress report, the recent understanding of the influence of oxygen supplied during deposition on the structural phase formation process is reviewed and supplemented with new data for mixed HfxZr1-xOy films. Even though polar and non-polar HfxZr1-xOy thin films are well characterized, little is known about the impact of oxygen exposure during the deposition process. Here, a combination of structural and electrical characterization is applied to investigate the influence of the oxygen and zirconium content on the crystallization process during ALD deposition in comparison to other deposition techniques. Different polarization properties are assessed which correlate to the determined phase of the film. Optimized oxygen pulse times can enable the crystallization of HfxZr1-xOy in a polar orthorhombic phase rather than a non-polar monoclinic and tetragonal phase.