Oxidant Concentration Modulated Metal/Silicon Interface Electrical Field Mediates Metal‐Assisted Chemical Etching of Silicon

Abstract

AbstractMetal‐assisted chemical etching (MacEtch) of silicon in HF aqueous solutions has attracted great interest due to its wide range of applications including photovoltaics, thermoelectrics, Li‐ion batteries, and bio/chemical sensors. However, to date, the understanding of MacEtch process is rather limited. In this work, the effects of the H2O2 concentration as well as the properties of silicon on MacEtch in HF‐H2O2 aqueous solutions are investigated in detail. It is found that for low oxidant concentration, the MacEtch rate of silicon is oxidant concentration dependent and doping type dependent. While for high H2O2 concentration, the MacEtch rate increases with increasing H2O2 concentration, but exhibits no evident dependence on doping types. An oxidant concentration modulated metal/silicon interface electrical field model is proposed for MacEtch of silicon on the basis of experimental findings and semiconductor/metal contact theory. The model shows that excessive holes' accumulation at the metal/silicon interface generates a spontaneously biased voltage at metal/silicon interface and changes the interfacial electric field and thereby the interface band bending, successfully explains the characteristics of MacEtch of p‐type and n‐type silicon while naturally explains many characteristics of MacEtch of silicon such as porosification of nanowires and silicon substrates, thus provides new insights into the MacEtch of silicon.