Plasma polymer films for 532 nm laser micromachining

Abstract

Laser micromachining with a frequency doubled Nd:YAG laser (532 nm) can replace more complex microlithographic processes for rapid turnaround in the development of prototype application-specific integrated circuits. Plasma polymerization 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 potential. The deposition rates, molecular structures, physical properties and optical properties of the polymers were characterized. PP(Ar/E), with relatively little oxygen and no nitrogen, with superior substrate adhesion and with no debris generated on laser micromachining was chosen as the optimal laser micromachining film. The PP(Ar/E) coefficient of optical absorption at 532 nm (α532), related to unsaturated group concentration, increased with the ratio of plasma power to ethylene mass flow rate [W/Fm(E)]. α532 reached an asymptote of 2.9 μm−1 at high W/Fm(E) and could be enhanced slightly using postpolymerization ultraviolet exposure. The optimum conditions were using Ar/E=1/1 and 75 W to produce a 0.6 μm thick film for micromachining at 2 J/cm2 focused 0.25 μm beneath the surface. The laser pulse in a 1.2 μm thick film was not fully developed at 2 J/cm2 and exhibited rounded corners at 4 J/cm2, indicating that multiple low energy pulses would be preferable. A complicated and densely packed pattern with several different pulse sizes in which neighboring holes from pulses in close proximity do not merge was accurately reproduced in PP(Ar/E) using laser micromachining.

Spectroscopic studies of the mechanism of reversible photodegradation of 1-substituted aminoanthraquinone-doped polymers

“…Photoinduced damage in dye-doped polymer matrices has been studied in various systems for different applications [85][86][87][88][89][90][91][92][93][94]. Sensitized photodegradation and photooxidation of polymers can be induced by photoinitiators, in which polymer degradation or oxidation can be initiated by free radicals originating from photodegradation of sensitizers; or by photosensitizers, in which excited sensitizers transfer energy to the polymer or oxygen to initiate photodegradation or photooxidation [85].…”

“…Studies on photooxidation or photodegradation of various sensitized polymers have been reported including sensitized PS [85][86][87][88] and sensitized PMMA [89,90]. Laser ablation of polymers can be induced with the assistance of photosensitizers using visible lasers at wavelengths of 351 nm [91], 488 nm [92], and 532 nm [93]. Fukumura et al proposed that the photon energy absorbed by anthracene, the sensitizer, is converted into thermal energy in PS, the polymer host, causing thermal decomposition [91].…”

The relationship between chemical structure and dielectric properties of plasma-enhanced chemical vapor deposited polymer thin films

“…Recently, considerable work has been undertaken to fabricate polymeric dielectric and photonic thin films using plasma enhanced chemical vapor deposition techniques (PECVD) [1][2][3][4][5][6][7][8] due to its room temperature, solvent-free and versatile operation. Many organic precursors can be selected to prepare thin polymer films with a wide range of compositions and chemical functionalities.…”

Interaction of Photons with Polymers: From Surface Modification to Ablation

“…Visible 131 and high repetition rate lasers are rather seldom used for ablation studies, but the high repetition rate lasers (usually in the kHz range, but up to 20 kHz) have been used for drilling and wire stripping in the electronic industry for several years. The ablation studies proved that cumulative heating influences the ablation behavior, i.e., showing increasing ablation rates 132,133…”