The essential points of this technique are the use of an ultrathin Pd catalyst on TaN by atomic layer deposition (ALD) and ultrasonic vibration in the electroless plating bath. We demonstrated Cu electroless deposition (ELD) on an ALD-Pd passivated TaN barrier layer. The Pd film deposited by ALD was 3 nm thickness on the TaN substrate and had good coverage with low surface roughness. For the Cu ELD process, we used ethylenediamine-tetraacetic acid (EDTA), glyoxylic acid, and additional chemicals such as polyethylene glycol, Re-610 and 2,2'dipyridine. The Cu ELD was performed at a temperature of 60-65° C for 30 min. The success of ELD Cu in gap filling a patterned TaN substrate with 130 nm openings and an aspect ratio of three is attributed to the removal of hydrogen gas from the surface by ultrasonic vibration for 1s after 15 min of deposition in the bath. In this work, we suggest the use of ultrasonic vibration in the Cu electroless plating bath without a chemical inhibitor. © 2005 The Electrochemical Society. All rights reserved.