The incorporation mechanism and annealing behavior of argon in magnetron-sputtered aluminum and aluminum alloy films were investigated. The incorporated argon concentration of Al alloy (Al-Si, AI-Cu) films was determined by X-ray fluorescence analysis as a function of impurity content (Si : 0-12 wt.%; Cu : 5 wt.%), argon pressure (0.2-1.6 Pa), cathode potential (500-700 V), and substrate temperature (without substrate heating and 250 degrees C). Hardly any argon atoms were incorporated into Al alloy films with a 250 degrees C pre-substrate heating temperature. For the sample prepared without substrate heating, in contrast the incorporated argon concentration in Al-Si alloy films increased linearly with increasing Si content in Al films. The argon concentration in Al alloy films increased with decreasing argon pressure and increasing cathode potential. The incorporation of argon in magnetron-sputtered Al-Si alloy film is attributed to the argon becoming entrapped in the amorphous silicon flux. Argon incorporated into Al alloy films by magnetron sputtering and argon implanted into Al films was not released even during 550 degrees C annealing.