The influence of alloying on the phase formation sequence of ultra-thin nickel silicide films and on the inheritance of texture

Abstract

The controlled formation of silicide materials is an ongoing challenge to facilitate the electrical contact of Si-based transistors. Due to the ongoing miniaturisation of the transistor, the silicide is trending to ever-thinner thickness's. The corresponding increase in surface-to-volume ratio emphasises the importance of low-energetic interfaces. Intriguingly, the thickness reduction of nickel silicides results in an abrupt change in phase sequence. This paper investigates the sequence of the silicides phases, and their preferential orientation with respect to the Si(001) substrate, for both 'thin' (i.e. 9 nm) and 'ultra-thin' (i.e. 3 nm) Ni films. Furthermore, as the addition of ternary elements is often considered in order to tailor the silicides' properties, additives of Al, Co and Pt are also included in this study. Our results show that the first silicide formed is epitaxial θ-Ni 2 Si , regardless of initial thickness or alloyed composition. The transformations towards subsequent silicides are changed through the additive elements, which can be understood through solubility arguments and classical nucleation theory. The crystalline alignment of the formed silicides with the substrate significantly differs through alloying. The observed textures of sequential silicides

Impurity-enhanced solid-state amorphization: the Ni–Si thin film reaction altered by nitrogen

“…Thin film growth has been studied extensively for several decades. [1][2][3] One particular way of growing thin films is to anneal two elemental films (or a film and a substrate) which are in contact which each other, creating compounds at the interface during the solid-state reaction. Special attention was given to reactions between a metal layer and Si substrates, due to the role of metal silicide growth as model system for solid-state reactions.…”

“…Efforts to understand the effects of impurities on metal silicide formation are ongoing. 3,13,14 Surprisingly, very little is known about the effect of impurities on the SSA reaction. J.J.…”

“…21 Additionally, investigation of this reaction is partly driven by the use of NiSi films as contact material in CMOS architecture. 3,22 The Ni-Si reaction is also a promising test case for the effect of impurities on the SSA reaction: it has been reported 23 that the reaction of the Ni-Si system starts off with the growth of an amorphous phase (see below). Moreover, it has been shown that the Ni-Si reaction can be strongly affected by impurities, 24 such as nitrogen, 25 carbon 26 and oxygen.…”

Further insights into the growth mechanism of the non-stoichiometric θ-Ni2Si phase

“…The formation of NiSi phase, via solid state reaction between Ni film (ec > 4,8nm) and Si(100), is preceded by a simultaneous formation of Ni-rich phases [1]. Recent studies have shown that the sequence of Ni-rich phases and their characteristics (texture, resistivity and interface quality) is altered by the substrate orientation [2], film thickness [1,3,4], the presence of dopants [5] and alloy elements [1,6,7]. The formation of Ni-rich phases is albeit evidenced for all preparation conditions.…”

Phonons and Thermal Expansion Behavior of NiSi and NiGe

“…NiSi (Franciosi et al, 1982 ; Lee et al, 2000 ; Detavernier et al, 2003 ; Jin et al, 2013 ), FeSi (Damascelli et al, 1997a , b ), CoSi (Acun and Soyalp, 2012 ), and similar compounds (Kim, 2015 ) have been extensively studied with above applications in mind, and also for their various unusual physical and chemical properties (Weber et al, 2006 ; Lin et al, 2015 ; Geenen et al, 2018 ). NiSi (Connétable and Thomas, 2009 ) is structurally similar to NiGe.…”