Studies of excimer laser etching mechanism using laser induced fluorescence measurements

Bombarding solid surfaces with intense 248 nm KrF* or 193 nm ArF* excimer lasers leads to rapid etching. The ejected material consists of atoms, diatomics and larger clusters. Using laser fluences near threshold so as to minimize perturbations due to gas-phase collisions and to laser-produced plasma, the energy distributions of the first two types of species were measured by laser-induced fluorescence (LIF). The species detected were Al, A10, C2 and CN. The results show that for a metallic-like material (graphite) the energies agree with a purely thermal mechanism for the vaporization. In distinct contrast to this, insulating materials (sapphire and polymers) display nonthermal energy distributions and point to a photochemical (bond-breaking) mechanism. Understanding these mechanisms is of interest to microelectronic circuit production techniques, to optical damage prevention, and to laser surgery. © 1987 SPIE.