Aluminum Reactive Ion Etching Employing CCl4+Cl2 Mixture

Abstract

Alumintun reactive ion etching has been investigated employing a CCl₄+Cl₂ mixture. Anisotropic etching was achieved at a self-bias voltage of –150V, a flowrate concentration of 50% Cl₂ in CCl₄ and 13.56 MHz rf power at 200 W. The photo-resist swelling, which is closely related to undercutting of the isotropic etching condition is attributed to the heat of reaction between neutral reactive species and Al. A mass analysis makes it clear that a CCl₄+Cl₂ plasma generates more CCl⁺ ₃ species while suppressing unsaturated monomers, and also reduces the water vapor. Decreasing the final pressure in the reactor shortens the initiation period, then it disappears for the anisotropic etching condition with CCl₄+Cl₂. A “load-lock” type reactor is confirmed to offer reproducible Al etching. Blowing hot air (\doteqdot200°C) over the wafers after etching was found to be an effective measure against rapid Al corrosion.