Direct bonding

Direct bonding, or fusion bonding, describes a wafer bonding process without any additional intermediate layers. The bonding process is based on chemical bonds between two surfaces of any material possible meeting numerous requirements.These requirements are specified for the wafer surface as sufficiently clean, flat and smooth. Otherwise unbonded areas so called voids, i.e. interface bubbles, can occur. Direct bonding, or fusion bonding, describes a wafer bonding process without any additional intermediate layers. The bonding process is based on chemical bonds between two surfaces of any material possible meeting numerous requirements.These requirements are specified for the wafer surface as sufficiently clean, flat and smooth. Otherwise unbonded areas so called voids, i.e. interface bubbles, can occur.