Removal of Plasma-Etch-Induced Polymers from Submicron Via Holes by Excimer Laser Ablation

Abstract

AbstractA relatively new approach in removing the sidewall and bottom polymers resulting from reactive ion etching of via holes, using a non-contact dry excimer laser cleaning technique has been investigated. Pulsed excimer laser ablation at 248 nm has been found to be capable of removing the via-etch-induced polymers at fluences limited by the damage threshold of the underlying Al-Cu metal film with TiN anti-reflective coating of 250-280 mJ cm-2. A fluence window of 150-200 mJ cm-2 for efficient laser cleaning is also determined from the ablation rate data using the relation in the limit of Beer's law absorption. Experimental results have also shown that the ablation rate when irradiating at an angle is not only comparable to that at vertical incidence, but even register higher values for most of the ablation rate data obtained. An optimum incident angle for laser cleaning of 45° can be determined from the results.