Al-Cu Alloy Etching Using In-Reactor Aluminum Chloride Formation in Static Magnetron Triode Reactive Ion Etching

We describe a new Al-Cu alloy etching system that uses aluminum chloride formed in the reactor to build deep-submicron Al-Cu laminated interconnections. The etching residue containing copper chloride after Al-Cu etching can be removed by a flow of aluminum chloride at a relatively low temperature of 120°C. This is because copper chloride reacts with aluminum chloride to form volatile chloroaluminate copper. In the new etching system aluminum chloride is formed through the use of a second cathode covered with aluminum targets in static magnetron triode reactive ion etching (SMTRIE). With this configuration, aluminum chloride flow can be precisely controlled and highly selective deep-submicron etching of Al-Cu laminated interconnections without any residue can be achieved. It is also shown that the aluminum chloride flow suppresses after-corrosion.