We used local probe techniques to characterize electron beam (e‐beam) induced changes in thin oxides on silicon. Primary effects of the 1 nm wide, 300 keV e beam included the formation of positive charges trapped in the SiO2, physical restructuring in the oxide, and deposition of carbonaceous compounds. Charges remained stable in thicker oxides (460 nm) and appeared as changes in the contact potential or microwave response with widths down to 100 nm. In thinner oxides (20 nm) the amount of charge was smaller and less stable; below 7 nm no charge was detected. Physical changes in the oxide, evident as a swelling of irradiated areas, accounted for the etching selectivity of these regions. ©1995 American Institute of Physics.