EXCIMER-LASER ABLATION OF POLYIMIDE-DOPED POLY(TETRAFLUOROETHYLENE) AT 248 AND 308 NM

Experimental data on the 248 and 308 nm wavelength excimer laser ablat ion at poly(tetrafluoroethylene) doped with polymide (PI) are reported for a range of fluences and dopant concentrations. Threshold fluences were determined and a correlation was obtained between the dopant con centration and the threshold fluence. The threshold fluences and the l imiting etch rates at high fluences decreased with increasing dopant c oncentration, and there is a minimum dopant concentration below which there is no ablation at both of the wavelengths. The side wall taper o f the ablated holes increased with increasing dopant concentration. At subthreshold fluences, the polymer surface was modified with selectiv e removal of PI from the polymer blend. The etch rates have been model ed using a two parameter thermal model to describe the etching process . The parameters obtained by fitting the data are qualitatively correl ated to the dopant concentration and the measured limiting etch rates.