Mechanism of Oxygen Redistribution During Ultra-Shallow Junction Formation in Silicon

The transport of dissolved oxygen in the Czochralski silicon towards the arsenic-doped ultra-shallow junction was investigated. Ultra-shallow junction was formed by low-energy As+ ion implantation with the subsequent furnace annealing at 7500C - 9500C temperatures for the dopant activation. Oxygen and arsenic redistributions were investigated by secondary ion mass spectrometry (SIMS) technique. The peculiarities of defect creation and transformation were studied by the X-ray diffuse scattering technique (XDS). It was found that oxygen concentration in the arsenic redistribution region is increased a few times already after 1 minute of annealing. Increase of annealing time leads to decrease of oxygen accumulation as a result of oxygen transportation to the SiO2/Si interface. As a result the thickness of screen silicon oxide is increased by 0.5 nm. This effect is related with the oxygen gettering from the wafer bulk. A physical mechanism of the oxygen transfer is discussed.