The erbium ions at energy of 400 keV and dose of 5× 10^15 ions/cm^2 were implanted into silicon single crystals at room temperature at the angles of 0°,45° and 60°. The lateral spread of 400 keV erbium ions implanted in silicon sample was measured by the Rutherford backscattering technique. The results show that the measured values were in good agreement with those obtained from the prediction of TRIM＇98 （Transport of Ions in Matter） and SRIM2006 （Stopping and Range of Ions in Matter） codes.
