We investigated the effect of the helium ion implantation on the etching rate of silicon nitride in hydrofluoric acid. Helium ions were implanted into 500-nm-thick silicon nitride film with energies from 15 keV to 35 keV. The ion fluence from 10(14) cm(-2) to 10(17) cm(-2) was used. All samples were investigated with a scanning electron microscope and atomic force microscope. The dependence of the etching rate on the concentration of ion-induced defects is obtained.