The formation of integrated circuit often involves etching metal layers. For example, aluminum-containing gate electrodes and aluminum copper pads are commonly seen integrated circuit components. These components are formed by depositing a blanket metal layer, and then patterning the blanket metal layer as desirable patterns using an etching process.
The etching of the metal layer may be performed in a dry etching chamber, which is vacuumed, and etching gases are introduced into the etching chamber to etch the metal layer. In the etching process, plasma is generated from the etching gases. The metal ions in the metal layer may sometimes react with the ions in the etching gases to form particles. For example, when aluminum is etched, the aluminum ions may react with fluorine ions to form aluminum fluorine (AlF) particles, which stick to the inner surface of the etching chamber. The bonding of the AlF particles to the inner surface of the etching chamber, however, is weak. Hence, the bonds between the AlF particles and the inner surface may break, and the AlF particles fall on wafers, causing manufacturing yield to drop.
AlF has a high vaporizing temperature. Hence, it is difficult to remove the AlF particles.