Effect of inert ion bombardment on chemisorption and etching of aluminum films in Cl2, Br2, CCl4, and CBr4

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Abstract
The role of ion bombardment on the reaction of Cl2, Br2, CCl4, and CBr4 with thin aluminum films has been investigated. Experiments were carried out in a UHV system equipped with an evaporation source, a quartz crystal microbalance, Auger electron spectrometer and x-ray photoelectron spectrometer. Clean Al thin films etched spontaneously in both Cl2 and Br2 beams without ion bombardment at room temperature. The spontaneous etch rates were approximately proportional to the halogen molecule pressure. The surface coverage of aluminum halides on the etched surfaces was very small (about 0.1 monolayer). The spontaneous etch rates and the chemical states of aluminum halides were not affected by argon ion bombardment. These results suggest a mechanism for the spontaneous etching of aluminum. Etch rates of Al by ion bombardment were significantly reduced in the presence of CCl4 and CBr4. Both were dissociatively chemisorbed on the clean Al surface forming a ‘‘carbidelike’’ layer. Ion bombardment changed the chemical states of the chemisorbed aluminum halide species.

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