Laser-assisted chemical etching of 1); Al thin films in 100 torr HCI gas atmosphere, 2); Cu thin films in 10% $H_2SO_4$ solution, and 3); Al thin films in 5% or 10% $H_3PO_4$ solution, are investigated and etching dynamics is investigated. The etching process depends upon local heating of the thin film by a focused $Ar^{+}$ ion laser beam. Therefore eching rate is a strong function of the absorbed laser power. The etching rate is determined by measuring the time required to pierce the thin film. Spatial temperature profile is calculated from steady-state thermal diffusion equations. The activation energies, which are calculated from the Arrhenian temperature dependence of etching rate, are 0.88, 0.72, and 0.34 eV/atom for Al in HCI gas medium, Al in $H_3PO_4$ solution, and Cu in $H_2SO_4$ solution, respectively. It is observed that $Ar^{+}$ ion laser-assisted etching rate can be as large as $10^6$ times the background etching rate for Al thin films in $H_3PO_4$ solution. As etching progresses, it is observed in the back reflected laser beam that a concentric circular fringe pattern appears and shrinks. The development of the etching process is explained by analyzing the circular diffraction patterns using an etched shape function of Gaussian nature.
