Precipitation Kinetics and Recombination Activity of Cu in Si in the Presence of Internal Gettering Sites

摘要

The recombination activity of Cu in Si and its precipitation kinetics in the presence of internal gettering sites has been investigated. It is suggested that copper precipitates are a major recombination center in p-type silicon. Their formation is retarded in p-type silicon due to large lattice strains and electrostatic effects. The electrostatic barrier for copper precipitation disappears when the Fermi level position, determined by the concentration of shallow acceptors (boron) and shallow donors (interstitial copper) reaches the electro-neutrality level of the precipitates. Comparison of the impact of Cu on minority carrier diffusion length obtained on p-Si samples with different resistivity yielded a proof of this electrostatic model. Studies of internal gettering of copper in samples with different density of oxide precipitates indicated that oxide precipitates are relatively inefficient as sinks for copper. This might be due to the compressive lattice strain generated by both oxide precipitates and copper precipitates. Our findings indicate that the morphology of oxide precipitates may have a strong impact on their gettering efficiency.