Raman scattering and x-ray photoelectron spectroscopy are used to study the damage induced by low energy Ar+ milling on InAs(100) surfaces. Evidence for etch-induced lattice damage is obtained even under the mildest conditions employed. Etching at 75 V creates an In-rich; surface and reduces the intensity of scattering from the unscreened longitudinal optic (LO) phonon in the near-surface region. Etching at higher voltages creates damage states that increase the carrier concentration at depths at least as large as the Raman probe depth (similar to 100 Angstrom). Post etch annealing at 500 degrees C in ultrahigh vacuum restores the LO phonon mode to its original, intensity, the carrier concentration to original levels, and a stoichiometric (In:As = 1:1) surface composition. Etch-induced lattice damage in the near-surface, region, which is subsequently removed by annealing at optimal temperatures, is the only mechanism consistent with all the inelastic light scattering and composition results.