Infrared emission and the threshold for excimer laser ablation of Kapton

Abstract

The threshold fluence for ablation of organic polymers is an important parameter in most micromachining applications. Changes in the chemistry and morphology of surfaces prior to ablation act as precursors to ablation, and can significantly modify the properties of irradiated material. We have obtained time dependent infrared emission spectra from the polyimide Kapton at fluences near the threshold for ablation with 308 nm excimer laser radiation. These spectra show that a variety of small molecular species are ejected from the surface prior to ablation. A comparison of these spectra with absorption spectra of Kapton irradiated with 308 nm or 10.6 μm laser radiation or thermally degraded by heating in air shows that the reaction with atmospheric oxygen can be an important effect. These data yield new insight into the effect of intense UV laser radiation on organic polymers.The threshold fluence for ablation of organic polymers is an important parameter in most micromachining applications. Changes in the chemistry and morphology of surfaces prior to ablation act as precursors to ablation, and can significantly modify the properties of irradiated material. We have obtained time dependent infrared emission spectra from the polyimide Kapton at fluences near the threshold for ablation with 308 nm excimer laser radiation. These spectra show that a variety of small molecular species are ejected from the surface prior to ablation. A comparison of these spectra with absorption spectra of Kapton irradiated with 308 nm or 10.6 μm laser radiation or thermally degraded by heating in air shows that the reaction with atmospheric oxygen can be an important effect. These data yield new insight into the effect of intense UV laser radiation on organic polymers.