The reaction of Cl2with a Si solid under Ar+ion bombardment is investigated theoretically by the classical trajectory method. The etching yield of Si is calculated and is in good agreement with recent experimental results. The main products of the reaction are atomic Si and Cl together with molecular SiCl and SiCl2. This is also consistent with experimental findings. We report calculations of product, energy, and angular distributions. The relevance of these calculations for the dry etching of semiconductors is discussed.