Excimer laser micromachining of structures using SU-8

Muralihar K. Ghantasala; Erol C. Harvey; Dinesh K. Sood

doi:10.1117/12.361208

30 August 1999 Excimer laser micromachining of structures using SU-8

Muralihar K. Ghantasala, Erol C. Harvey, Dinesh K. Sood

Author Affiliations +

Proceedings Volume 3874, Micromachining and Microfabrication Process Technology V; (1999) https://doi.org/10.1117/12.361208
Event: Symposium on Micromachining and Microfabrication, 1999, Santa Clara, CA, United States

Abstract

The ablation characteristics of the photoresist SU-8 under 248 KrF excimer pulsed laser radiation have been studied. The variation of SU-8 etch rate with fluence has been investigated in the range 0.05 J/cm² to 3.01 J/cm². Threshold fluence for ablation of SU-8 is measured to be about 0.05 J/cm². The etch rate of SU-8 is found to be higher than that of polyimide under identical conditions. The curves for etch rate dependence on fluence are in agreement with those reported in the literature for polyimides and also obey a theoretical model. We have investigated the effect of different prebake temperatures on the ablation characteristics which are found to be similar for all temperatures. The effect of increasing the number of laser shots has been examined at different fluences to understand the etch rate variation near the 'end of film' stage of ablation. The results of our analyses of these samples using SEM, profilometery and optical microscopy reveal - very smooth morphology of the etched surfaces without significant debris, no noticeable damage to underlying silicon, gradual build up of a carbonaceous film outside and around the etch pits. We find SU-8 very suitable for rapid excimer ablation lithography which has been demonstrated by patterning a gear structure in an SU-8 resist layer with aspect ration of 4.5.

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Muralihar K. Ghantasala, Erol C. Harvey, and Dinesh K. Sood "Excimer laser micromachining of structures using SU-8", Proc. SPIE 3874, Micromachining and Microfabrication Process Technology V, (30 August 1999); https://doi.org/10.1117/12.361208

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