Role of bubbles in laser-assisted wet etching

Abstract

Evidence is presented to explain laser-based aqueous salt etching in terms of vapor bubble growth conditions at the irradiated surface of a substrate. The effect of pulse and frequency modulation of a cw laser is investigated to determine growth behavior for adhering bubbles in pure water. The role of salt in solution (such as KOH, NaOH, or CaCl2) is discussed in terms of its function as a diffusion barrier for growing vapor bubbles. Etching data are presented for the case of a Cu-vapor laser applied to a Mn-Zn-ferrite substrate, comparing results with and without KOH in the etching solution.