Characterization of Nanometer‐Sized Oxygen Precipitates in Highly B‐Doped Czochralski Silicon

Abstract

We use a wide variety of analytical methods to characterize nanometer‐sized oxygen precipitates in highly B‐doped Czochralski (CZ) silicon. Due to the enhanced precipitation of oxygen in this type of wafer, the precipitate density reaches a value of 1 × 1013 cm−3 already after short annealing. On the one hand, this provides an excellent possibility for testing the detection limits of different methods and on the other hand the knowledge on oxygen precipitation in p+ material can be broadened. In order to study density, size, and morphology of oxygen precipitates, we exploit scanning transmission microscopy (STEM), reactive ion etching (RIE), and preferential etching. STEM is also used to determine size distribution and energy dispersive X‐ray spectroscopy (EDX) and electron energy loss spectroscopy (EELS) are used to investigate the composition of oxygen precipitates. In annealed samples, oxygen precipitates, dislocation loops, and stacking faults are found. The dislocation loops disappear after long annealing in contrast to the stacking faults which are detected in all samples annealed at 1000 °C. It is found that the long anneal at 1000 °C leads to the formation of two size fractions of precipitates. This process is similar to Ostwald ripening. The precipitates are octahedral, consist of SiO2 and the B concentration is below the detection limit of the methods used here. The obtained results are in good agreement with the nucleation model of highly doped wafers proposed by Sueoka.