Atmospheric pressure excimer lamp-assisted photoselective activation process for electroless plating

Photoselective activation technologies for electroless metallisation have significant potential in minimising the number of activation process steps. In this work, a novel photo-selective activation process for electroless plating is described. The process is based on the selective photodecomposition of a palladium based precursor using a purpose built 222 nm KrCl) excimer lamp contact mask aligner. The photoexposure conditions to produce a selective palladium activation are detailed. Previously reported maximum pressure thresholds 1 mbar.for an efficient photoprocess have been overcome. This has been achieved using a triple excimer lamp source to increase ultraviolet UV.intensity, a substrate temperature of 70–858C and an organometallic precursor having a ligand to metal charge transfer optical absorption peak at 224 nm corresponding to the peak output of the KrCl) excimer lamp. Activation is reported at atmospheric pressure in a N2 ambient, removing the need for processing under vacuum. Electroless copper features with a lateral resolution of 50 mm are demonstrated. The electroless metallisations are characterised in terms of adhesion performance, resistivity and resistance to peel-off during sawing. q1999 Elsevier Science B.V. All rights reserved.