Kinetics of silanol condensation for low-temperature direct bonding

This paper presents first results of fracture surface energies measurements performed in-situ during annealing of silicon wafers. The effect of wafer conditioning by atmospheric-pressure plasmas and subsequent chemical pretreatments was investigated. High surface energies are obtained at low annealing temperatures by plasma-treatment in N2+O2 mixtures without any post-treatment. The increase of surface energy during annealing of O2 -plasma treated wafers is considerably accelerated by post-treatment with gaseous or aqueous NH3. Aside from a catalytic effect of NH3 on siloxane formation, cationic bridging of bonding surfaces by NH4 + must also be considered at low annealing temperatures.