Phase formation and texture of thin nickel germanides on Ge(001) and Ge(111)

Abstract

We studied the solid-phase reaction between a thin Ni film and a single crystal Ge(001) or Ge(111) substrate during a ramp anneal. The phase formation sequence was determined using in situ X-ray diffraction and in situ Rutherford backscattering spectrometry (RBS), while the nature and the texture of the phases were studied using X-ray pole figures and transmission electron microscopy. The phase sequence is characterized by the formation of a single transient phase before NiGe forms as the final and stable phase. X-ray pole figures were used to unambiguously identify the transient phase as the-phase, a non-stoichiometric Ni-rich germanide with a hexagonal crystal structure that can exist for Ge concentrations between 34% and 48% and which forms with a different epitaxial texture on both substrate orientations. The complementary information gained from both RBS and X-ray pole figure measurements revealed a simultaneous growth of both the-phase and NiGe over a small temperature window on both substrate orientations. V

Reaction of Ni film with In0.53Ga0.47As: Phase formation and texture

“…5 While no tilted fiber texture (typical of axiotaxy) was observed on pole figures, we can consider the following: the [111] axis is a three-fold rotational axis that can easily adjust with the six-fold rotational c axis of the hexagonal structure. Thus, the growth occurs only through epitaxial relationship with the substrate as it was described for -NiGe by De Schutter et al 26 (see Table II). The calculated mismatch according to the description of the alignments at the beginning of this paragraph is summarized in Table III for both intermetallic domains.…”

“…Indeed, every set of three (0001) hexagonal planes should meet every set of two (111) substrate planes at 2 points. 26 The occurrence of an axiotaxy, where lattice planes of the intermetallic are aligned with lattice planes of the substrate, is a possible explanation for the group B orientation. Moreover, the high roughness of the so-formed film is likely to favor the occurrence of an axiotaxy-like alignment.…”

Texture in thin film silicides and germanides: A review

“…31 In the following years, detailed texture studies of different silicide and germanide materials were carried out using this technique, revealing axiotaxy in a considerable number of silicide/germanide materials (see Table I). More recently, the use of a linear or area detector instead of a point detector 37,38 and the introduction of EBSD as a complementary technique 41 have enabled the ability to perform unambiguous phase identification of highly textured transient phases that form during the formation of NiSi 33,35 or NiGe 103 (see Section IV A). In the near future, area detectors will be routinely used to record texture information in situ, enabling the study of texture evolution during silicide/germanide formation.…”

“…Pole figure measurements at different stages during the reaction towards NiGe have revealed the presence of a similar transient hexagonal, metastable germanide, i.e., -Ni 5 Ge 3 , forming epitaxially before the formation of NiGe on both Ge(001) and Ge(111) substrates. 121 From the discussion above, it is clear that texture measurements at different stages during a solid-state reaction can provide valuable information in order to identify the phase(s) present at different temperatures during the formation sequence, especially when the forming phases are heavily textured. Furthermore, the orientation of the single crystalline substrate has a strong effect on the texture of the different phases in the formation sequence, leading to different interfaces and interface energies for different substrate orientations.…”

Improving the morphological stability of nickel germanide by tantalum and tungsten additions

“…5 Nickel germanide is studied as a material for contact metallization of the source and drain terminals of a Ge-MOSFET, owing to its low resistivity and compatibility with a self-aligned process. 6,7 The formation of the desired lowresistivity phase NiGe usually occurs via the high-resistivity, metal-rich phase ε-Ni 5 Ge 3 [8][9][10] and NiGe is also the last phase to form. The applicability of thin NiGe layers, however, is limited by the tendency to agglomerate (i.e to break up into islands) at lower temperatures than its NiSi counterpart in Si-MOSFETs.…”