It is known that the RCA Standard Clean 1, which is used repeatedly during device fabrication, can cause etching of Si. In some process flows, such etching can be important when fabricating devices with thin films, for example, in silicon-on-insulator technology. We show that 25-30 Angstrom of Si is etched away by a modified version of the SCl clean (1:8:64 parts by weight of NH4OH, H2O2, and H2O), when it is applied for 10 min to a bare Si layer on top of SiO2.