Ion beam modification of the Ni-Si solid-phase reaction: The influence of substrate damage and nitrogen impurities introduced by ion implantation

Abstract

We report on the growth of thin NiSi films via the thermal reaction of Ni layers (13 -35 1 nm) with Si(100) substrates modified by ion implantation. By introducing substrate 2 damage or nitrogen impurities prior to the solid-phase reaction, several properties of 3 the NiSi films can be modified: the formation temperature, texture, diffusion-limited growth rate and morphological stability. As some of the modifications to the NiSi 5 films are rooted in the early silicide phases preceding the NiSi phase, particularly its 6 formation temperature, special attention is devoted to the growth of the amorphous 7 Ni-Si alloy and the crystalline δ-Ni 2 Si and θ-Ni 2 Si phases.8We employed a number of experimental techniques, including in situ synchrotron 9 X-ray diffraction (XRD), in situ Rutherford backscattering spectrometry (RBS), in 10 situ sheet resistance measurements, ex situ ion beam channelling and ex situ pole 11 figure measurements. We show that both the formation temperature of the NiSi films and the intensity of epitaxial and axiotaxial components of the NiSi texture 13 can be either lowered or raised by selecting appropriate implantation conditions. 14 Agglomeration of the NiSi films at high temperature (> 700 • C) can be slowed down, 15 either by slowing down the mobility of the Ni and Si atoms, or by removing the 16 morphologically destabilizing axiotaxial texture. Our results emphasize the strong 17 interwoven nature of phase formation, texture and morphological degradation. We 18 illustrate that the kinetics of the early stages of thin film reactions consist of more 19 than just diffusion, i.e. nucleation can also play a crucial role. 2 Page 2 of 36 AUTHOR SUBMITTED MANUSCRIPT -JPhysD-124461.R1 14 upon further annealing. 4 Extensive research, however, has revealed the appearance of two 15 metastable phases during the reaction. The first is an amorphous interlayer, preceding the 16 crystalline phases. It forms upon deposition and grows slightly upon subsequent annealing. 17 Nucleation barriers initially prevent the formation of crystalline phases; 6 during this time 18 the amorphous phase can grow up to a few nm. 7 For most films (≥ 10 nm), the amorphous 19 phase crystallizes long before the metal supply is consumed. The second metastable phase 20 observed in the reaction is the θ-Ni 2 Si phase, which appears in the film during the growth of 21 the δ-Ni 2 Si phase; both phases grow simultaneously for a brief temperature window before 22 the θ-Ni 2 Si phase is consumed. Not only is the concurrent growth of multiple phases in thin 23 film reactions uncommon, the appearance of the θ-Ni 2 Si phase is remarkable in itself, since 24 the phase is thermodynamically unstable below 825 • C. 8 Nevertheless, it has been observed 25 in Ni-Si reaction at relatively low temperature under a variety of experimental conditions. 9 26 27 It has been found that both metastable phases mentioned above, the θ-Ni 2 Si phase and 28 the amorphous interlayer, can be stabilized (i.e., their temperature window extended) by 29 various me...

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In Situ Study of the Interface-Mediated Solid-State Reactions during Growth and Postgrowth Annealing of Pd/a-Ge Bilayers

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