TEM INVESTIGATION OF INTERFACIAL OXIDE LAYERS BETWEEN DIRECTLY BONDED SILICON-WAFERS

The influence of the oxygen interstitial concentration and that of the crystallographic misorientation on the interfacial oxide layer between directly bonded silicon wafers were investigated by transmission electron microscopy. Wafers with different concentrations of oxygen interstitials were bonded or rotated around their common axis perpendicular to the wafer plane and bonded. Depending on the starting concentration of oxygen interstitials in the wafer, the interfacial oxide layer grows or shrinks. If the rotational angle is larger than a critical value theta-crit, the disintegration of the interfacial oxide layers is energetically less favorable than than keeping a continuous oxide layer. The critical angle to keep a continuous oxide layer is determined to be between 1 and 3-degrees.