Low-temperature thermal oxide to plasma-enhanced chemical vapor deposition oxide wafer bonding for thin-film transfer application

Low-temperature direct plasma-enhanced chemical vapor deposition (PECVD) oxide to thermal oxide bonding is described. The PECVD oxide is densified at 350 °C and chemical-mechanically polished to obtain reasonably smooth surface for bonding. The PECVD oxide wafer is bonded to the thermal oxide wafer at room temperature after piranha clean that leaves the wafer surfaces hydrophilic. A postbonding anneal at 300 °C completes the bonding. A void-free bonding interface is observed from infrared imaging and the bonding strength is estimated to be 432 mJ/m2. This bonding method can be used in a variety of applications, including three-dimensional integration.