Stress Buildup Upon Crystallization of GeTe Thin Films: Curvature Measurements and Modelling

Abstract

Phase change materials are attractive materials for non-volatile memories because of their ability to switch reversibly between an amorphous and a crystal phase. The volume change upon crystallization induces mechanical stress that needs to be understood and controlled. In this work, we monitor stress evolution during crystallization in thin GeTe films capped with SiOx, using optical curvature measurements. A 150 MPa tensile stress buildup is measured when the 100 nm thick film crystallizes. Stress evolution is a result of viscosity increase with time and a tentative model is proposed that renders qualitatively the observed features.

The microstructure and electrical and optical properties of Ge–Cu–Te phase-change thin films

“…It is well known that the phase change between the amorphous and the crystalline phase is accompanied by a large volume change, which results in pronounced stresses in thin films. 54 Thus the stress in crystalline thin films is another reason being considered. The stress was determined within the crystal lattice by measuring the shift in the position of a selected diffraction peak 2 θ = 26° for various tilt angles ( ψ = 0°, 9°, 18°, 27°, 33°, 39°, and 45°), and the residual stress causing the strain was estimated by using the assumption of a linear elastic distortion.…”