PREFERENTIAL LATERAL CHEMICAL ETCHING IN REACTIVE ION ETCHING OF ALUMINUM AND ALUMINUM-ALLOYS

Reactive ion etching of aluminum and its alloys in CCl//4/argon plasmas produces vertical etch profiles and residue-free etched regions. However, under certain conditions, preferential lateral chemical etching occurs, which produces pits in the surface of the metal along the edges of the lands. The lateral etching is due to a thermally activated process and is related to the structure of the films. The extent of attack can be reduced by annealing the films at 450 degree C before etching. Al-Cu films deposited onto heated substrates are more susceptible to attack than those evaporated at lower temperatures. This apparent contradiction has not been resolved. The effects of etching temperature, plasma parameters, and film structure will be discussed. Scavenging of the responsible species by additions of H//2 or O//2 to the plasma is not successful.