EFFECTS OF COPPER AND OXYGEN PRECIPITATION DURING THERMAL-OXIDATION OF SILICON - AN ELECTRON-BEAM-INDUCED CURRENT STUDY

The effects on minority carrier diffusion length L(n) of the oxidation of p-type silicon in a copper-contaminated ambient have been analyzed using an electron-beam-induced current. The experiments were carried out on Czochralski (Cz) and float-zone silicon, and on samples with da maged and undamaged surfaces, in order to evaluate the role of oxygen supersaturation in the starting material, and the influence of the for mation of oxidation-induced stacking faults on oxygen and copper preci pitates during the oxidation anneal. The microstructure of the interfa ce silicon underlayers was controlled using transmission electron micr oscopy and secondary ion mass spectrometry. The diffusion length L(n) was drastically decreased in regions free of copper colonies, showing that a noticeable concentration of copper existed in the form of point like recombinant defects in the bulk. This effect was more pronounced in Cz silicon, where it was assigned to the presence of oxygen-based c lusters acting as copper traps, and in the cases of damaged surfaces, where it indicated that the growth of the copper-related pointlike def ects occurred with the emission of silicon self-interstitials. (C) 199 5 American Institute of Physics.