A discussion of mainstream plasma-activated wafer bonding as used in SOI production has demonstrated the following benefits over conventional bonding: creation of bonded substrates at temperatures below 400 degrees centigrade; achievement of full mechanical strength with excellent electrical or optical properties; and generation of new possibilities for layered semiconductor materials since thermal expansion differences are eliminated or minimized. Plasma-activated bonding continues to supplant traditional wet chemical-activated direct bonding for Si fusion bonding, delicate microelectromechanical sensors (MEMS) structures, and anodic bonding applications where applied voltage is no longer acceptable. Topics covered include basic chamber design and kinetics. Plasma-activated wafer bonding uses ionized gas atoms to change the surface conditions of a substrate. Plasma bonding is often done with oxygen plasmas for applications requiring electrical isolation at the interface, and hydrogen, nitrogen, or argon plasmas in applications needing a direct or conductive bond interface. Plasma-activated bonding equipment requires a large process window, integration to alignment stages, and conformity to industry standards for safety and cleanliness. With the plasma method, processing times and temperatures can be reduced, while full-strength bonds and bulk interface properties are maintained.