Analysis and improvement of interfacial adhesion of growth-dominant Ge-doped SbTe phase change materials

Abstract

A semiquantitative characterization of the interfacial adhesion of phase change materials is developed, which consists of determining critical adhesion temperature (TCA) via measuring the probability of adhesion failure with temperature using patterned films. By comparison of TCA values, Ge-doped SbTe (Ge-ST) is shown to have weaker adhesion than Ge2Sb2Te5 (GST), which results from its limited ability in relaxation of crystallization-induced stress. Nitrogen or oxygen doping in Ge-ST produces significant increase in TCA, close to that of GST. This improvement is due to smaller grain size of N-/O-doped Ge-ST, which facilitates the relaxation of the stress via grain boundary diffusion or sliding.

Si–Sb–Te materials for phase change memory applications

“…film drops to about ∼5.2 mN @ 573 K, which is less than that of crystalline Si 2 Sb 2 Te 6 film ∼8.9 mN @ 573 K, as shown in figure 8. Crystallization induced thickness shrinkage and the resulting high stress will make film adhesion on the substrate decrease [37]. This explanation is consistent with our results of thickness reduction that Si 2 Sb 2 Te 6 has less thickness change than that of Ge 2 Sb 2 Te 5 .…”

“…Si-rich Si x Sb 2 Te 3 films Si 3.5 Sb 2 Te 3 and Si 5 Sb 2 Te 3 have larger L c compared with Ge 2 Sb 2 Te 5 and Si 2 Sb 2 Te 6 . In addition, a smaller grained crystalline microstructure is supposed to promote the stress relaxation, which will improve the surface adhesion with the substrate [37]. With more Si doping in Sb 2 Te 3 material, the crystal grains will be effectively confined in smaller size after annealing, thus resulting in a better interface adhesion.…”

Investigation on the role of nitrogen in crystallization of Sb-rich phase change materials

“…7 In the case of Sb-rich phase change materials such as Ge-doped SbTe ͑Ge-ST͒, N-addition has not been studied as much. 8 Compared with the case of GST, Sb is a prevailing constituent and Ge is a minor additive in these materials. Besides, these materials display growth-dominated mode of crystallization, characterized by a rapid growth of a small number of nuclei, contrary to nucleation-dominated mode of GST.…”

Study on Interface Adhesion between Phase Change Material Film and SiO2 Layer by Nanoscratch Test

“…Finally, the residual stress or the stress relaxation is also crucial for the adhesion strength of PCM films, since the smaller the residual stress is, the higher adhesion becomes. 32) From the XRD results reported before, 25,27) the grain size of the crystalline SST film, which is deduced from the full width at half maximum (FWHM) of the diffraction peak, is smaller than that of GST as Si in the crystalline SST film remains in amorphous state and confines the grain size effectively. 31) For both of the nucleation-dominant materials, it seems rational that more paths for atomic diffusion and larger probability for grain sliding can be provided by smaller grain size, thus promoting stress relaxation in the interfaces.…”