Thermo-chemical Etching of Si₃N₄

Abstract

A low power CO₂ laser was used to perform localized etching on Si₃N₄ coated with an aqueous KOH solution, and the etching characteristics were investigated. The laser power density is less then 10 kW/cm², and Si₃N₄ cannot be etched only by laser irradiation. However, coating with an aqueous KOH solution, the surface can be etched by laser irradiation. The etching process is not accompanied by melting but by oxidation. The etching rate depends on the laser power density and the concentration of the KOH solution. The etched area is restricted to the laser irradiated area. The etched hole diameter depends on the laser power density, and it is possible to form an etched hole whose diameter is less than the one of the laser beam.