Highly Selective AlSiCu Etching Using BBr3 Mixed-Gas Plasma

The effect of selectivity to photo resists when exposed to gas plasma containing Br is studied in AlSiCu etching. The magnetron enhancement reactive ion etching reaction of AlSiCu employs a BBr3/Cl2 gas mixture in comparison with the conventional Cl-containing gas process of SiCl4/Cl2. Selectivity to photo resists increases with increase in the magnetic field when the BBr3/Cl2 process is employed, but not when the SiCl4/Cl2 process is employed. Further, selectivity to photo resists peaks at the concentration of 10% to 20% BBr3. The mechanism behind the highly selective etching is the production of a C-Br compound on the photo resist during AlSiCu etching. This C-Br compound strongly protects the surface of the photo resist. This deposit on the film restrains the etching rate of the photo resist, and high selectivity to the photo resist is obtained by using the gas process containing Br.