Structural and electrical characterization of silicided Ni/Au contacts formed at low temperature (<300 °C) on p-type [001] silicon

Abstract

Silicided Ni/Au contacts with very low contact resistance were realized on p-type [001] silicon at low temperature by ex-situ or, alternatively, by in situ annealing processes. During the ex-situ annealing, performed at 200 °C for 10 s, a uniformly thin (14 nm) Ni2Si layer was formed having an extremely flat interface with silicon thanks to the trans-rotational structure of the silicide. During the in situ annealing, promoted by a sputter etch processing (T < 300 °C), a 44 nm-thick silicide layer was formed as a mixture of trans-rotational NiSi and epitaxial NiSi2, domains. In both cases, using a low thermal budget has guaranteed a limited consumption of silicon during the reaction process and a good adhesion with the substrate avoiding gold contaminations. As a consequence of the presence of trans-rotational domains, wherein a pseudo-epitaxial relationship between the silicide and the silicon lattices is established, an ohmic behavior was observed in a wide range of substrate doping (3.5 × 1018 ÷ 3 × 1019 B/cm3) for both annealing processes (in situ and ex-situ). On the other hand, conventional TiNiAu and CrNiAu contacts showed, in the same range of B doping concentration, a rectifying behavior with systematically higher specific contact resistance values (Rc) compared to those of the Ni silicided contacts.

Nanoscale study of the current transport through transrotational NiSi/n-Si contacts by conductive atomic force microscopy

“…It is well assessed that the use of nickel silicide on source and drain contacts of microelectronic devices has a significant impact to reduce series and contact resistances. 1,2 The drastic scaling down of devices and also the recent interest to use plastic substrates, which have low critical temperatures (e.g., Tc polyimide 200 C), pose more and more the need to optimize the material properties, and particularly, the interfaces quality on the nanoscale. It is thus mandatory to know in more detail the process of silicide formation since the very early stages of the reaction process to control the structure and the stoichiometry of the silicide, especially on very thin layers.…”

Structural characterization of in‐situ silicided contacts textured on p‐type [001] silicon

“…Cross-sectional transmission electron micrographs, representing samples labelled as 1, 2, 3 and 4 in (a), (b), (c) and (d), respectively, offer in addition the possibility to study the interface between Ni silicide and Si, showing that the flattest one is obtained with 60 s of sputter etching (b) and (d), while the least flat one is reached by skipping that procedure (a). The deterioration of interface slightly visible in (c) is ascribable to the increasing of surface temperature and can be related to the remarkable worsening of interface, leading to the formation of pyramidal protrusions, reported for longer sputter etching steps and higher temperatures [7][8][9]. XRD analyses (not shown), performed in grazing incidence configuration, have also revealed for all the studied samples the predominance of Ni reach phases, instead of the Si reach ones reported for longer sputter etching steps [7,8,10].…”

“…The deterioration of interface slightly visible in (c) is ascribable to the increasing of surface temperature and can be related to the remarkable worsening of interface, leading to the formation of pyramidal protrusions, reported for longer sputter etching steps and higher temperatures [7][8][9]. XRD analyses (not shown), performed in grazing incidence configuration, have also revealed for all the studied samples the predominance of Ni reach phases, instead of the Si reach ones reported for longer sputter etching steps [7,8,10].…”

“…For this reason, the peculiar alignment between the obtained silicide layer and the Si substrate, since it involves the interface structure, is expected to positively impact the electrical behaviour of the silicided contacts. Similar structurally coupled contacts, when used as backside metallization in P-channel MOS were, in fact, previously reported to exhibit a lower specific contact resistance than traditional schemes, and also a good adhesion with the Si substrate [7][8][11][12][13][14].…”

NiSi2 formation through annealing of nickel and dysprosium stack on Si(100) and impact on effective Schottky barrier height

“…17. In our latest study, we find that the formation of nickel disilicide (NiSi 2 ) phase [19][20][21][22] is the underlying reason for the reduction in U B n,eff for Ni-Dy silicided contact devices.…”