EXCIMER-LASER ETCHING OF DIAMOND-LIKE CARBON-FILMS - SPALLING EFFECT

Etching of diamond-like amorphous hydrogenated carbon films by 20 ns p ulses of a KrF excimer laser has been investigated. In addition to pre viously reported etching mechanisms realized via either carbon oxidati on or vaporization, a new etching mode based on a spalling effect was observed. It was found that there is a narrow window in laser fluences in which the etch rate of the carbon films examined exceeds by nearly two orders of magnitude the etch rates measured at fluences beyond th is interval. The effect of anomalously fast etching occurs below a thr eshold for normal laser ablation (vaporization), and is ascribed to st ress-induced lift-off of the material in the form of 30-60 nm thick ma croscopic sheets. Very smooth surface relief in the etched crater and a reduced degree of film graphitization are characteristic features of this new etching mode.