Kinetics and coupled dynamics of dewetting and chemical reaction in Si/$\hbox {SiO}_2$/Si system

Abstract

We report on the observation of a coupling between the dewetting of a Si layer on $\hbox {SiO}_{{2}}$ induced by surface/interface energy minimization and the etching between both materials due to the $\hbox {Si}+\hbox {SiO}_{2}\longrightarrow 2$$\hbox {SiO}^\uparrow _g$ reaction. In the limit of a thin $\hbox {SiO}_{{2}}$ layer ($\le 10 \,\hbox {nm}$) sandwiched between a Si layer and a Si handle wafer, the front of Si dewetting and the front of $\hbox {SiO}_{{2}}$ 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 $\hbox {SiO}_{{2}}$ 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 $\hbox {SiO}_{{2}}$ layer in the center. These processes are thermally activated with an activation energy of $2.4\pm 0.5 \,\hbox {eV}$ and $4.0\pm 0.5 \,\hbox {eV}$, respectively, for dewetting and the etching reaction. All these results highlight the respective roles of wetting and etching in Si/$\hbox {SiO}_{{2}}$/Si system dynamics and could be a stepping stone for the development of advanced processes based on Silicon-On-Insulator technology.