Encapsulation Effects on Ge‐Rich GeSbTe Phase‐Change Materials at High Temperature

Abstract

Ge‐rich GeSbTe chalcogenide alloys have gained significant attention in the field of phase‐change materials due to their remarkable thermal stability and thus their suitability for integration in nonvolatile memories targeting embedded automotive applications. Herein, the effects of different encapsulating materials on the evolution and on the crystallization kinetic of N‐doped Ge‐rich GeSbTe films are focused on. These films are annealed with temperatures compatible with the back‐end‐of‐line of the complementary metal‐oxide‐semiconductor (CMOS) fabrication. First, it shows how the encapsulation layer thickness should be tuned in order to protect the layer from oxidation and at the same time to avoid delamination phenomena. TaN, C, TiN, SiC, and SiN used as encapsulating layers are compared. The segregation and crystallization of Ge‐rich GeSbTe alloys appear more homogeneous in the case of C, TiN, and SiC. On the contrary, the effects of an interfacial heterogeneous nucleation in the case of TaN and SiN are observed. It results in a different final morphology of the chalcogenide layer after annealing depending on the encapsulation, with different grain sizes and kinetic of phase separation.