THE STABILITY OF THIN INTERFACIAL SIO2 LAYERS IN DIRECTLY BONDED CZOCHRALSKI AND FLOAT-ZONE SILICON-WAFER PAIRS

The stability of thin interfacial SiO2 layers in directly bonded silicon wafer pairs is investigated by means of high-resolution transmission electron microscopy. The results are explained by using a classical nucleation theory. It is shown that the interfacial oxide layers in bonded Czochralski (CZ) grown silicon wafer pairs is structurally more stable than those in bonded float-zone (FZ) silicon wafer pairs. The effect of internal diffusion of the oxygen atoms in the silicon wafer on the interfacial oxide layers is demonstrated to be negligible. The higher stability of the interfacial layers in CZ silicon wafer pairs is attributed to the higher concentration of interstitial oxygen which can resist the disintegration by increasing the system free energy.