Spatially selective crystallization of ferroelectric Hf0.5Zr0.5O2 films induced by sub-nanosecond laser annealing

Abstract

In this work we study the sub-nanosecond laser-induced crystallization of 10 nm-thick atomic layer deposited amorphous Hf0.5Zr0.5O2 (HZO) films in an air atmosphere. We used an infrared laser with 1064 nm wavelength and 800 ps pulses to anneal TiN/HZO/TiN capacitors by scanning an 80 μm-diameter spot along their top surface in a controlled way. The laser annealing process was optimised in terms of fluence to achieve the complete crystallization of HZO into a non-monoclinic polymorph, as demonstrated by X-ray diffraction and transmission electron microscopy. Piezoresponse force microscopy and polarization-field loops confirm that the optimal as-annealed HZO films are piezoelectric and ferroelectric from the first cycle on. Spatial selectivity was accomplished by scanning the laser on selected areas of the samples. Micro-diffraction experiments show that the transition between the crystallized and the amorphous region is abrupt within a distance of several hundred µm.