High-rate and highly directional reactive ion etching of copper films is examined by adding Cl-2 and NH3 to the SiCl4 and N-2 mixture. The etching rate of copper increases with increasing Cl-2 flow rate at temperatures higher than 280 degrees C. However, the addition of Cl-2 causes side etching of the Cu patterns. Adding NH3 forms a SiN-Like protective film that prevents side etching. The sidewall taper can be controlled by the NH3 flow rate and etching gas pressure because the formation of the SiN-like protective film depends on these parameters. Fine Cu patterns are obtained by reactive ion etching with a SiCl4, N-2, Cl-2, and NH3 mixture, achieving an etching rate about six times higher than that with a SiCl4 and N-2 mixture.