Oxygen precipitation and secondary defects in silicon by high energy ion implantation and two-step annealing

Abstract

Intrinsic gettering is usually used to improve wafer quality which is an important factor for reliable ultralarge scale integration devices. The two-step annealing method was adopted to investigate the oxygen precipitates and secondary defects in the aspect of various nucleations and growths for 1.5 MeV, 1×1015 As/cm2 implanted wafers. After two-step annealing, the wafers were cleaved and etched with Wright etchant. Oxygen precipitation density observed by optical microscope in lightly boron doped samples was very low. However, in heavily boron doped samples, the density of oxygen precipitation was the largest at 600 °C in the first annealing, and decreased abruptly until 800 °C. But it increased slightly from 800 to 1000 °C and was independent with the implantation. The location and type of secondary defects were inspected by high resolution transmission electron microscopy. The aligned dislocation was located in the vicinity of the amorphous/crystalline interface in the case of the first annealing temperature of 600 °C. But the dislocations climbed to the surface for the first annealing temperature of 700–1000 °C. The difference indicated that the nucleation might be occurring at the first annealing of 600 °C but growth of defects occurred at 700 °C or above.