A method of forming a bonded assembly includes providing a first semiconductor die containing and first metallic bonding structures and a first dielectric capping layer containing openings and contacting distal horizontal surfaces of the first metallic bonding structures, providing a second semiconductor die containing second metallic bonding structures, disposing the second semiconductor die in contact with the first semiconductor die, and annealing the second semiconductor die in contact with the first semiconductor die such that a metallic material of at least one of the first metallic bonding structures and the second metallic bonding structures expands to fill the openings in the first dielectric capping layer to bond at least a first subset of the first metallic bonding structures to at least a first subset of the second metallic bonding structures.

A semiconductor device includes a lower structure and an upper structure on the lower structure. The lower structure includes a first semiconductor substrate, a first pad and a first dielectric layer. The first dielectric layer surrounds the first pad and exposes a top surface of the first pad. The upper structure includes a second semiconductor substrate, a second pad and a second dielectric layer. The second dielectric layer surrounds the second pad and exposes a bottom surface of the second pad. The first pad and the second pad are bonded to each other across an interfacial layer to couple the upper and lower structures to each other. The first and second pads and the interfacial layer include a same metallic material. The first and second pads have a substantially same average grain size and the interfacial layer has a different average grain size than the first and second pads.

A hybrid bonding apparatus that is able to reduce metal contamination is provided. The hybrid bonding apparatus may include a plasma treater configured to perform a pulsed plasma surface treatment on a first wafer, wherein the first wafer includes a bonding pad; a pulse controller connected to the plasma treater and configured to control on/off of a pulse of the pulsed plasma surface treatment; a cleaner configured to clean the first wafer; a bonder configured to bond the first wafer and a second wafer to each other; and an equipment front end module (EFEM) configured to load the first wafer and the second wafer, and unload the first wafer and the second wafer, after being bonded together.

An element, a bonded structure including the element, and a method of forming the same are disclosed. The bonded structure can include a first element having a first nonconductive field region and a first conductive feature. A surface of the first nonconductive field region and a surface of the first conductive feature at least partially defining a bonding surface of the first element. The first conductive feature includes a first portion and a second portion over the first portion and at least partially defines the surface of the first conductive feature. The first portion includes aluminum. The first conductive feature has a continuous sidewall along the first portion and the second portion. The second portion includes different metal composition from the first portion or comprising fluorine at the surface of the first conductive feature. The bonded structure can include a second element having a second nonconductive field region and a second conductive feature. A surface of the second nonconductive field region is directly bonded to the first nonconductive field region without an intervening adhesive along a bond interface and a surface of the second conductive feature is directly bonded to the second conductive feature without an intervening adhesive along the bond interface.