Surface activated bonding (SAB) is a low-temperature

wafer bonding Wafer bonding is a packaging technology on wafer-level for the fabrication of microelectromechanical systems (MEMS), nanoelectromechanical systems (NEMS), microelectronics and optoelectronics, ensuring a mechanically stable and hermetically sealed ...

technology with atomically clean and activated surfaces. Surface activation prior to bonding by using

fast atom bombardment Fast atom bombardment (FAB) is an ionization technique used in mass spectrometry in which a beam of high energy atoms strikes a surface to create ions. It was developed by Michael Barber at the University of Manchester in 1980. When a beam of high ...

is typically employed to clean the surfaces. High-strength bonding of

semiconductor A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. ...

metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typi ...

, and

dielectric In electromagnetism, a dielectric (or dielectric medium) is an electrical insulator that can be polarised by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the m ...

can be obtained even at room temperature.

Overview

In the standard SAB method, wafer surfaces are activated by argon

ultra-high vacuum Ultra-high vacuum (UHV) is the vacuum regime characterised by pressures lower than about . UHV conditions are created by pumping the gas out of a UHV chamber. At these low pressures the mean free path of a gas molecule is greater than approximately ...

(UHV) of 10⁻⁴–10⁻⁷ Pa. The bombardment removes adsorbed contaminants and native oxides on the surfaces. The activated surfaces are atomically clean and reactive for formation of direct bonds between wafers when they are brought into contact even at room temperature.

Researches on SAB

The SAB method has been studied for bonding of various materials, as shown in Table I. The standard SAB, however, failed to bond some materials such as SiO₂ and polymer films. The modified SAB was developed to solve this problem, by using a sputtering deposited Si intermediate layer to improve the bond strength. The combined SAB has been developed for SiO₂-SiO₂ and Cu/SiO₂ hybrid bonding, without use of any intermediate layer.

Technical specifications

References

{{Wafer bonding Wafer bonding Semiconductor technology Electronics manufacturing Packaging (microfabrication) Semiconductor device fabrication Microelectronic and microelectromechanical systems