Silicon layer transfer by hydrogen implantation combined with wafer bonding in ultrahigh vacuumRoom-temperature bonding of lithium niobate and silicon wafers by argon-beam surface activation
The onset of surface blistering in hydrogen-implanted single crystalline silicon was studied. A combination of atomic force microscopy and optical measurements shows that hydrogen-containing platelets grow laterally below silicon surface until they suddenly pop up as surface blisters due to the internal hydrogen pressure after a critical size has been reached. Experimentally and theoretically, the critical size of the onset blisters was found to increase with increasing implantation depth or top layer thickness.
The crack opening method is widely used for the determination of the surface energy of two bonded wafers, which is associated with the energy required to separate bonded wafers. In the present paper the dependence of the measured surface energy of bonded silicon wafers on the time after insertion of a blade at various pressures, silanol group densities, and annealing temperatures is reported. At normal conditions (air pressure, room temperature, 30% humidity) a strong dependence of the effective surface energy on the insertion time is found for wafers which were annealed at 200, 400, and 900°C. For bonded wafers without subsequent annealing this phenomenon is not observed. Additional measurements under reduced pressure show that the debonding process appears to be related to the adsorption and chemical reaction of water molecules at sites of broken bonds at the opened surfaces. We conclude that a meaningful comparison of measured surface energies requires detailed information on the measurement conditions. push pull
In silicon wafer bonding, the initial contact area spreads laterally with a typical speed on the order of 10 mm/s. We observed that this lateral bonding speed increases with decreasing ambient pressure, and is independent of the distance of the contact front to the rim of the wafers and independent of wafer thickness. From these results, we conclude that the lateral bonding speed is mainly determined by pressing the ambient gas out between the two wafers from a very localized area close to the propagating bonding front.
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