Surface activated bonding


Surface activated bonding is a low temperature wafer bonding technology with atomically clean and activated surfaces. Surface activation prior to bonding by using fast atom bombardment is typically employed to clean the surfaces. High strength bonding of semiconductor, metal, and dielectric can be obtained even at room temperature.

Overview

In the standard SAB method, wafer surfaces are activated by argon fast atom bombardment in ultra-high vacuum 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.
SiGeGaAsSiCCuAl2O3SiO2
Si
Ge
GaAs
SiC
Cu
Al2O3
SiO2Failure

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.
Bonding intermediate layerReferences
SiO2-SiO2Sputtered Fe-Si on SiO2
Polymer filmsSputtered Fe-Si on both sides
Si-SiCSputtered Si on SiC
Si-SiO2Sputtered Si on SiO2

The combined SAB has been developed for SiO2-SiO2 and Cu/SiO2 hybrid bonding, without use of any intermediate layer.
Bond interfaceReferences
SiO2-SiO2Direct bond interface
Cu-Cu, SiO2-SiO2, SiO2-SiNxdirect bond interface

Technical Specifications