This work presents atomic force microscopy (AFM) results on Surface imaging of ultrathin SiO2 oxides with thickness similar to10 nm. The SiO2 was grown by 850 degreesC dry oxidation of (100)Si substrates which underwent RCA wet and dry hydrogen plasma procedures prior to oxidation. The pre-oxidation cleans lead to significantly smooth Si surfaces, but on the hydrogenated silicon surfaces formation of hillocks is observed. Oxidation of silicon. although yielding a smooth outer oxide surface, enhances generation of hillocks. The biggest roughness and the most nonuniform distribution of hillocks are obtained on oxides formed on silicon treated in plasma at 300 degreesC. (C) 2002 Elsevier Science B.V. All rights reserved.