Cr. Davis et al., DOPANT-INDUCED EXCIMER LASER ABLATION OF POLY(TETRAFLUOROETHYLENE), Applied physics. B, Photophysics and laser chemistry, 54(3), 1992, pp. 227-230
Poly(tetrafluoroethylene) (PTFE) does not exhibit excimer laser etchin
g behavior at conventional, e. g., single photon absorption, emissions
of 193, 248, and 308 nm, due to the lack of polymer/photon interactio
n. This is not surprising since the electronic transitions available t
o the PTFE molecule are high energy and thus require short wavelength
the radiation However, by incorporating a small quantity of material i
nto the non-absorbing fluoropolymer matrix that interacts strongly wit
h the emitted laser energy, e.g., a dopant, successful ablation, both
in terms of etch rate and structuring quality occurs. Specifically, ex
cimer laser ablation of PTFE films containing 5, 10, and 15% polyimide
(wt/wt) as a dopant was achieved at 308 nm in a fluence range of 1 to
12 J/cm2. Ablation rates for the materials increased with increasing
fluence and, at the polyimide levels investigated, varied inversely wi
th dopant concentration. All compositions exhibited excellent structur
ing quality.