Mechanical Properties of Phase-change Recording Media: GeSbTe Films

Abstract

Mechanical properties of as-deposited GeSbTe media on SiO 2 /Si(100) with different compositions and film thicknesses were successfully investigated by using the microcantilever method and nanoindentation. All the studied films show a compressive residual stress state, which increases proportionally to the elastic constant. Because of the accumulating effects during film deposition, the mechanical properties of these GeSbTe films can be greatly affected. As the film thicknesses were 20 and 25 nm, compared with the Ge 4 SbTe 5 and Ge 4 Sb 0.5 Te 5 Bi 0.5 films, the Ge 2 Sb 2 Te 5 film has the highest residual stress value ranging from 3 MPa to 15 MPa. When the film thickness was 30 nm, the composition-induced stress relaxation occurred. Bi addition, which leads to lattice expansion in Ge 4 SbTe 5 films, resulted in a decrease of stress. Compared with the Ge 4 SbTe 5 and Ge 4 Sb 0.5 Te 5 Bi 0.5 films, the Ge 2 Sb 2 Te 5 film also has the lowest coefficient of thermal expansion (CTE) value ranging from 2×10 −6 to 7×10 −6 / • C, and a lower CTE was obtained when the film thickness was increased. By nanoindentation, the Ge 4 SbTe 5 film shows higher hardness and elastic constant than those of the Ge 2 Sb 2 Te 5 film. The measured hardnesses for Ge 2 Sb 2 Te 5 and Ge 4 SbTe 5 films are 12 GPa and 18 GPa; and the reduced elastic modului are 120 GPa and 140 GPa, respectively.

Elastic Modulus of Amorphous Ge2Sb2Te5 Thin Film Measured by Uniaxial Microtensile Test

“…For these reasons, the mechanical properties of Ge-Sb-Te thin films have been investigated using various experimental techniques, such as wafer curvature measurements, [3,5,6] nanoindentation tests, [6][7][8] and Brillouin light scattering. [9] However, uniaxial microtensile tests of Ge-Sb-Te thin films have yet to be reported, most likely due to the difficulty in specimen fabrication inherent in Ge-Sb-Te thin films, although microtensile tests of thin films of gold, silicon, and aluminum [10][11][12] have been conducted.…”

Young's modulus and residual stress of GeSbTe phase-change thin films

“…These properties have not been extensively investigated and a large variation 60 of reported values can be found in literature [19,20]. Knowledge on the compositional dependence of these properties and their variation with temperature facilitates the choice for the correct composition for a particular application.…”

How important is the {103} plane of stable Ge2Sb2Te5 for phase‐change memory?

“…The transient thermal stress is therefore generated in the material during the rapid heating, (Zhang et al, 2002;Zhou et al, 1997) and the maximum thermal stress can be given as (Zhang et al, 2006;He et al, 2000) σ max =E α T where the Young´s modulus E is 35 GPa, (Agarwal et al, 2010) the thermal expansion coefficient a is (2ß7)×l0 −6 K −1 . (Jong et al, 2001) Based on the T estimated above, the maximum thermal stress will reach 140ß490 MPa. Therefore the nonequilibrium thermal compressive stress will be one of the main effects on the phase transition.…”