REMOVAL OF CU IMPURITIES ON A SI SUBSTRATE BY USING (H2O2+HF) AND (UVO-3+HF)/

Cleaning the Si surface has become one of the most critical steps of t he ultra-large-scale integration process. One of the major concerns is the removal of metallic impurities on the Si surface. In this study, we concentrate on the metallic impurity Cu. The Si substrate was clean ed with piranha(H2O4 : H2O2 = 4 : 1) and HF (HF : H2O = 1 : 100) solut ions to eliminate the organic impurities and the native oxide. The ini tial Si substrate was then contaminated intentionally by dipping it in to a 1-ppm standard solution of Cu followed by cleaning splits of a ch emical HF solution combined with a UV/O-3 treatment and a chemical mix ture of HF with H2O2 The initial substrate; which had been contaminate d with the standard solutions of Cu, exhibited a contamination level o f 10(14) atoms/cm(2). This substrate was cleaned and showed a Cu impur ity concentration which had been reduced down to the levels of 10(9) s imilar to 10(10) atom/cm(2) as measured by total reflection X-ray fluo rescence. Also, repeated treatments with these cleaning splits improve d the surface microroughness of this initial substrate from 3.6 Angstr om, to 1.8 Angstrom, as which by atomic force microscopy. The surface and the interface morphologies were examined by scanning electron micr oscopy and transmission electron microscopy. The results showed that t he Cu impurities had been adsorbed on the Si surface not in a thin fil m but in a particular form with a hemispherical shape. Both the chemic al compositions of the Cu impurities and the interface between the Cu and the Si substrate were investigated by Auger electron spectroscopy.