Effect of Surface Oxygen Concentration on Wafer Strength in Floating Zone Si Wafers

Abstract

The critical stress behavior of low-oxygen-concentration silicon wafers was elucidated by measuring the critical stress of slip generated owing to scratches using the high-temperature three-point bending test method. It is well known that floating zone (FZ) wafers with low oxygen concentrations tend to easily cause slips from dislocation sources such as scratches. The first point observed in the study is that the critical shear stress of FZ wafers had no temperature dependence above 973 K, which may suggest the presence of long-range obstacles for dislocation motion. The second point is that slip generation from scratches was less likely to occur when oxygen atoms were inwardly diffused into the wafer surface by high-temperature thermal treatment. These results will contribute to solving the problem of slip generation from backside scratches, often created during the insulated gate bipolar transistor manufacturing process in which FZ wafers are used.