Investigation of the formation of undercut during the fabrication of silicon microchannels by electrochemical etching

Silicon microchannel plates have been explored intensively for numerous applications especially for weak light detection and night vision. The electrochemical etching in hydrofluoric acid-based solutions is known as a technique for porous silicon formation. This paper presents a new process for the formation of microchannel structure and the separation of the Si MCP from p-type starting substrates by a single-step electrochemical etching in HF-based electrolytes. High aspect ratio microchannels are fabricated by electrochemical etching and the conditions under which the undercut occurs are investigated. The formation of the undercut is found to be primarily determined by both current density and HF concentration, which determine the MCP structure thickness as well.