Mechanics of laser-assisted debonding of films

Films of GaN and ZnO can be separated from the substrates on which they are grown by the use of a laser-assisted debonding process in which a pulsed l aser is shone through the substrate and absorbed in the film. Experience sh ows that the success in separating the films intact and damage free depends sensitively on the laser parameters used and the physical and geometric pr operties of the films. In this contribution, the mechanics of the laser-ass isted debonding of GaN films are presented and used to construct process ma ps that delineate the conditions for damage-free film separation. The key v ariable is the nondimensional group OmegaE(p)/(d(p)(2)root tau), where Omeg a is a lumped material constant, E-p is the laser pulse energy, d(p) is the diameter of the illuminated area and tau is the laser pulse length. Experi mental observations of UV/excimer laser assisted debonding of GaN films fro m sapphire substrates are used to illustrate the types of deformations and cracking modes on which the process maps are based. (C) 2001 American Insti tute of Physics.