• Berre, Martine Le
• Chevalier, Céline
• Baboux, Nicolas
• Deleruyelle, Damien
• Romeo, Pedro Rojo
• Bouaziz, Jordan
• Vilquin, Bertrand

Abstract

HfO2 is known to exist in three different crystal phases at normal pressure:monoclinic phase at 300K, a tetragonal phase above 2050K, and finally a cubic phase above 2803K. The stable region of the tetragonal phase extends to lower temperatures in nanoscale crystallites due to the surface energy effect. As a consequence, the crystallization in thin films tends to proceed by nucleation in a tetragonal phase and a martensitic transformation to the monoclinic phase during crystal growth. This phase transformation involves volume expansion and shearing of the unit cell. The admixture of sufficient SiO2 (between 5 and 10 mol.%) has been found to stabilize the tetragonal phase in HfO2 but in 2011, it was also reportedthe presence of ferroelectric and antiferroelectric crystalline phases in SiO2-doped HfO2 thin films grown by atomic layer deposition [1]. Based on X-ray diffraction measurements, it was argued that the ferroelectric phase is orthorhombic with a Pca21 space group. The occurrence of ferroelectricity in Si:HfO2 is remarkable as it represents one of very few metal oxides which are thermodynamically stable on silicon, leading to enable a number of device concepts relying on silicon/ferroelectric heterostructures. Various applications have been suggested for fluorite-structure ferroelectrics due to their advantages over the conventional perovskite-structure ferroelectrics [2]. We focus on (Hf,Zr)O2 (HZO) thin films deposition for the capacitor of Ferroelectric Random Access Memories (FRAM) in the 1Transitor-1Capacitor (1T-1C) model. (Hf,Zr)O2 thin films are studied to either fully understand the stabilization of the ferroelectric phase (f-phase) by atomic layer deposition and RF magnetron sputtering or to fit with industrial requirements [3].References: [1] T.S. Bockle et al., Appl. Phys. Lett. 99, 102903 (2011). [2] M.H. Park, et al., MRS Commun. 1 (2018). [3] J. Bouaziz et al., ACS Applied Electronic Materials 1 (9), 1740 (2019).

Topics

• perovskite
• impedance spectroscopy
• surface
• x-ray diffraction
• thin film
• crystalline phase
• physical vapor deposition
• Silicon
• random
• crystallization
• space group
• surface energy
• atomic layer deposition