Crystallization characteristic and structure of hafnium addition in germanium antimony thin films for phase change memory

Highlights: • The thermal stability were improved upon an increase in the Hf content. • The grain size reduced due to the presence of amorphous Hf-Ge and Hf-Sb content. • The volume change became smaller as a result of the confined grain size. • The cell based on Hf_0.14(Ge₅Sb₉₅)_0.86 thin film exhibits a relatively fast switching speed and lower power consumption. -- Abstract: The influences of Hf addition on the phase change character of Ge₅Sb₉₅ thin films were systematically studied. The heat induced crystallization was evaluated by in situ resistance measurement. By doping Hf element, both the resistance and the crystallization activation energy rise, resulting in better thermal stability and higher operating energy efficiency. Various analysis indicate that due to the existed amorphous germanium and antimony element, the hafnium addition can delay the growth of crystal grains and constrain the crystal size. A shift in the Raman mode corresponding to Sb after crystallization can be observed. By using the X-ray reflectance and atomic force microscope, it is observed that after doping Hf, the volume fluctuation and the surface roughness decrease. To evaluate the electrical characteristics, a phase change memory chip based on Hf doped Ge₅Sb₉₅ thin film was also fabricated successfully. The results show that proper incorporation of Hf with Ge₅Sb₉₅ is an helpful method for adjusting and optimizing the crystallization properties of the material in the applications of the phase change memory.