Recent observations on „swirl defects” in dislocation-free silicon

Abstract

The generation of swirl etch pits in dislocation-free silicon wafers is studied in more detail. It is found that a small hillock arises in most cases prior to the appearance of an etch pit. There are various particular shapes of pits in the initial stage. Only on further etch attack these pits transform into the well-known flat-bottomed and triangular shapes. From this it is concluded that small stacking faults or related defects are responsible for the swirl-etch pit formation. Precipitation of oxygen or hydrogen around the defects may occur causing the initial hillock formation.