Microfeature edge quality enhancement in excimer laser micromachining of metal films by coating with a sacrificial polymer layer

Abstract

A novel technique for enhanced excimer laser micromachining of metallic thin films by first coating the metal film with a thin polymer film is presented. The sacrificial polymer film acts as a protective and a clamping layer, preventing the metal film from undergoing cracking and damage during the laser ablation. The machined patterns are characterized regarding their quality in terms of edge roughness, lateral overcut and boundary integrity in proximity machining. Significant improvement in these aspects is observed when the machining is carried out on metal films coated with thin polymer films. Details of the effects of the fluence and spot overlap on the micromachined patterns are investigated. The technique allows sharp machining of micropatterns on thin metal films, over length scales ranging from hundreds of micrometers down to a single micrometer, thereby proving to be the only technique that can be used to laser micromachine thin films at the length scale of a single micrometer. This technique is expected to be useful for large scale patterning of metallic films, particularly for plasmonic applications and infrared/terahertz metamaterials.

Excimer laser micromachining of oblique microchannels on thin metal films using square laser spot

“…This is because the 1 lm thick polymer layer gets ablated within a few nanoseconds of the beginning of the pulse [12]. This is because the 1 lm thick polymer layer gets ablated within a few nanoseconds of the beginning of the pulse [12].…”

“…Chromium films [chromium being a refractory metal [12]], undergo cracking during irradiation with excimer lasers [18]. Cracking occurs irrespective of the film getting ablated or not.…”

“…It has been demonstrated in one of our earlier works [12] that excimer laser micromachining of a thin metal film can be made precise by coating the metal film with a sacrificial thin film of a polymer, whereby the polymer film protects the metal film from tearing during the ablation process. Thus, it is a better (simpler and quicker) alternative to various other techniques currently being used to fabricate the above-mentioned devices.…”

Analytical study for the selection of mask size and shape for obtaining high machining quality of complex features

“…24 Furthermore, in the literature, studies had been carried out to understand the effect of the spot overlap on the machined channel roughness at an oblique angle and concluded that roughness decreases with the increase in the overlap. 25 However, in the literature, the researchers had not discussed the effect of varying spot overlap on the machining time “T m .” Given that machining time is an essential factor in an industrial environment where a high production rate is required along with superlative quality of the product, a study for optimum spot overlap is required. Furthermore, the effect of mask shape on machining roughness and machining time has not been discussed in the literature.…”