CONTROLLED INHIBITION OF BREAKDOWN EFFECTS IN ELECTROCHEMICAL ETCHING OF SILICON AND ITS USE TO PREPARATION OF HIERARCHICAL NETWORKS OF OUT-OF-PLANE/IN-PLANE PORES

Back-side illumination of n-type silicon electrode during electrochemical etching in HF-based electrolytes is shown, for the first time, to inhibit electric breakdown at high anodic voltages (in the breakdown region). This has breakthrough effects on silicon electrochemistry, as it enables silicon dissolution to be controlled at the higher anodic voltages, thus increasing etching flexibility and, in turn, enabling the preparation of novel porous silicon micro and nanostructures, which are otherwise not feasible with the current technology level. In this work, exper- imental evidence of breakdown inhibition through back-side illumination of silicon electrodes etched in HF-H2O2 electrolyte is provided. Further, as a case of study, application of breakdown inhibition to the preparation of hier- archical networks of pores consisting of ordered out-of-plane macropores interconnected by smaller in-plane sec- ondary pores is reported.