Recently, the transmission electron microscope (TEM) has been used to study the formation and geometry of defect colonies in annealed and quenched silicon and in thermally oxidized and boron diffused silicon. The purpose of the present study was to examine subsidiary defect formation which can occur during the climb of Frank partial dislocations bounding stacking faults in boron diffused and subsequently thermally oxidized silicon. In these experiments, a {001} epitaxial silicon wafer (n-type, 1Ω−cm) was boron diffused (to 5×1018/cm3), and then steam oxidized for 2 hr at 1050°C. Prior to oxidation the wafer was cleaned using HF as a last step. After oxidation the oxide layer was first removed and then specimens from the wafer were chemically thinned from the substrate side for TEM observations (200 kV).