DRY ETCHING

PURPOSE:To achieve a highly accurate etching treatment that is free from side-etching without reducing an etching speed by causing gaseous ions for forming a sidewall protective coat to come to only a sidewall of a pattern. CONSTITUTION:Contributing to form a sidewall protective coat, a gas B is introduced into an ion-gun 11 through a conduit 10 and its gas B is ionized in the ion-gun 11. There is a pressure of about 0.1 pa (10 Torr) inside of a sample chamber 5 and an average free path of a molecule is several tens of centimeter. Therefore, ions of the gas B emitted from the ion-gun 11 come to a wafer 6 almost without having any collision of flying ions as shown in Fig. by a flow B so as to form the protective coat at a pattern sidewall. Then a wafer holder 7 holding the wafer 6 is rotated and driven by a motor 9 through a gear 8 and ion beams 13 are uniformly incident on the sidewalls of respectrive grooves in all the directions. Since an etching treatment can be performed to a bottom face, thereby protecting the wallsides, this approach helps avoid some of side-etching without reducing an etching speed and carry out a highly accurate processing.