Phase formation during Mn thin film reaction with Ge: Self-aligned germanide process for spintronics

Abstract

Interesting results have been reported concerning the magnetic properties of the Mn5Ge3 compound, opening the road to possibly create spin injectors in Ge. However, a process compatible with the Complementary Metal Oxide Semiconductor technology, allowing to produce a Mn5Ge3 layer on the active regions of Ge-based transistors has not been well established yet. Here, we report on the solid state reaction between a 50 nm-thick Mn film and amorphous Ge, aiming to investigate a similar process than the one (Salicide) used for contact production in the standard Si technology. In situ X-ray diffraction combined with ex situ structural and magnetic characterizations were used to identify and study phase formation during the Mn/Ge reaction.

High Curie temperature Mn5Ge3 thin films produced by non-diffusive reaction

“…In situ XRD measurements (not presented here) showed the same phase formation sequence as in the case of RD between a polycrystalline Mn film and an amorphous Ge layer deposited by e-beam evaporation [5]. Only two phases are observed in the sequence, the first phase being Mn 5 Ge 3 and the second phase being Mn 11 Ge 8 .…”

“…Only two phases are observed in the sequence, the first phase being Mn 5 Ge 3 and the second phase being Mn 11 Ge 8 . However, in the case of e-beam evaporation, Mn 5 Ge 3 was found to form at T ~ 210 °C and to transform into Mn 11 Ge 8 at T ~ 310 °C [5], while in the present case, Mn 5 Ge 3 was found to form at ~ 240 °C and to be stable up to temperatures as high as 400 °C. In the case of Mn 5 Ge 3 formation by NDR, in situ XRD measurements showed only the formation of Mn 5 Ge 3 at T ~ 225 °C.…”

“…In addition, six diffraction peaks at 2 = 30.9°, 35.8°, 38.7°, 42.7°, 43.8°, and 56.7°, corresponding respectively to the atomic planes (111), (002), (210), 5 (211), (112), and (311) of Mn 5 Ge 3 are also observed. No peak belonging to Mn 11 Ge 8 can be detected [5]. For the NDR sample, the same six diffraction peaks corresponding to Mn 5 Ge 3 are also observed, with an additional peak at 2 = 46.3°, corresponding to the Mn 5 Ge 3 (202) planes.…”

“…1). They correspond to the 200 nm-thick Ge layer that crystallized during annealing [5]. In addition, six diffraction peaks at 2 = 30.9°, 35.8°, 38.7°, 42.7°, 43.8°, and 56.7°, corresponding respectively to the atomic planes (111), (002), (210), 5 (211), (112), and (311) of Mn 5 Ge 3 are also observed.…”

Electronic properties of manganese impurities in germanium

“…Recently the attractiveness of this technology was further increased as it was shown that these ferromagnetic contacts can be fabricated on the active regions of Ge-based devices by means of a solid state reaction that is compatible with CMOS technology. [6] The origin of the ferromagnetism has been assigned to the formation of Mn 5 Ge 3 crystallites and Mn precipitates in the structure, which were not created in boron doped reference specimens. [7] Although the phase of interest, Mn 5 Ge 3 , is easily produced, it is difficult to keep it stable during subsequent device fabrication process steps.…”