Kinetics and coupled dynamics of dewetting and chemical reaction in Si/ $$\hbox {SiO}_2$$ SiO 2 /Si system
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Kinetics and coupled dynamics of dewetting and chemical reaction in Si/SiO2/Si system F. Leroy1,*
1 2
, D. Landru2, F. Cheynis1, O. Kononchuk2, P. Mu¨ller1, and S. Curiotto1
Aix Marseille Univ, CNRS, CINAM, Marseille, France SOITEC, Parc Technol Fontaines, 38190 Bernin, France
Received: 4 May 2020
ABSTRACT
Accepted: 23 August 2020
We report on the observation of a coupling between the dewetting of a Si layer on SiO2 induced by surface/interface energy minimization and the etching between both materials due to the Si þ SiO2 ! 2 SiO"g reaction. In the limit of a
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thin SiO2 layer ( 10 nm) sandwiched between a Si layer and a Si handle wafer, the front of Si dewetting and the front of SiO2 etching coexist in a narrow region. The interplay between both phenomena gives rise to specific morphologies. We show that extended Si fingers formed by dewetting are stabilized with respect to Rayleigh–Plateau-type instability over tenth of microns thanks to a localized etching of the SiO2 layer. The breakup of this structure occurs abruptly by an unzipping process combining dewetting and etching phenomena. We also put in evidence that Si rings are created with a thin SiO2 layer in the center. These processes are thermally activated with an activation energy of 2:4 0:5 eV and 4:0 0:5 eV, respectively, for dewetting and the etching reaction. All these results highlight the respective roles of wetting and etching in Si/SiO2 /Si system dynamics and could be a stepping stone for the development of advanced processes based on Silicon-On-Insulator technology.
Introduction Wetting of liquids on solids in reactive systems is of great importance with many industrial applications such as soldering or adhesion [1]. The kinetics of reactive wetting is affected by a number of factors like interfacial reactions, diffusion of constituents or
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https://doi.org/10.1007/s10853-020-05161-w
dissolution of the substrate [2, 3]. Under reaction, the contact line dynamics can lead to complex behaviors such as oscillatory phenomenon of spreading and contraction [4–7], formation of reaction rings [8] or even droplet motion [9–11]. For example, the reaction-mediated spontaneous drift of millimeter-scale solid-state camphor particles on the surface of water has been known for several centuries [12]. In solid
J Mater Sci
(a)
(b)
Figure 1 a Low-energy electron microscopy image of the dewetting of a SOI film ( 20 nm thick) at 1160 K. b Sketch of the dewetting mechanism: A Si finger destabilizes by a lateral undulation (time t1 ) that leads to beading and formation of a 3D Si island at its extremity (time t2 t1 þ 120 s). This process repeats periodically (time t3 t1 þ 240 s).
systems, only scarce studies have explored the coupling between chemical reactions and wetting dynamics. For instance, in metallic systems the alloying driving force can induce the self-propelled motion of
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