Impact of O-2 plasma surface pretreatment time is analyzed for Si-Si and SiO2-SiO2 low-temperature bonding wafer. It demonstrates there is an optimal O-2 plasma pretreatment time at which high and uniform bonding strength as well as drastic reduction of annealing bubbles can be reached. Our experimental results prove that plasma exposure time of the bonded interfaces is a crucial factor in ensuring high quality wafer bonding. (C) 2004 The Electrochemical Society.