Plasma polymer films for 532 nm laser micromachining

Laser micromachining with a frequency doubled Nd:YAG laser (532 nm) can rep lace more complex microlithographic processes for rapid turnaround in the d evelopment of prototype application-specific integrated circuits. Plasma po lymerization is a rapid, dry, environmentally friendly process that yields crosslinked pinhole-free films. Plasma polymerized films of ethylene and an additional gas [PP(gas/E)] were investigated for their micromachining pote ntial. The deposition rates, molecular structures, physical properties and optical properties of the polymers were characterized. PP(Ar/E), with relat ively little oxygen and no nitrogen, with superior substrate adhesion and w ith no debris generated on laser micromachining was chosen as the optimal l aser micromachining film.; The PP(Ar/E) coefficient of optical absorption a t 532 nm (alpha(532)) related to unsaturated group concentration, increased with the ratio of plasma power to ethylene mass flow rate [W/F-m(E)]. alph a(532) reached an asymptote of 2.9 mu m(-1) at high W/F-m(E) and could be e nhanced slightly using postpolymerization ultraviolet exposure. The optimum conditions were using Ar/E=1/1 and 75 W to produce a 0.6 mu m thick film f or micromachining at 2 J/cm(2) focused 0.25 mu m beneath the surface. The l aser pulse in a 1.2 mu m thick film was not fully developed at 2 J/cm(2) an d exhibited rounded corners at 4 J/cm(2) indicating that multiple low energ y pulses would be preferable. complicated and densely packed pattern with s everal different pulse sizes in which neighboring holes from pulses in clos e proximity do not merge was accurately reproduced in PP(Ar/E) using laser micromachining. (C) 1998 American Vacuum Society. [S0734-211X(98)00906-8].