Plasma characteristics and properties of Cu films prepared by high power pulsed magnetron sputtering

Abstract

Copper (Cu) has been proposed as a well-known material for metallization in Si-based semiconductor devices because of its low resistivity, high chemical stability, and excellent electromigration resistance. In order to improve the properties of Cu films further, the films were deposited on a Si (100) substrate using high power pulsed magnetron sputtering (HPPMS) by varying the substrate bias voltage. The Cu plasma characteristics and film properties were investigated as well. It was found that both electrons and ions contribute to the overall species current on the substrate. Electrons dominate the species current at the beginning and positive ions contribute the majority at end of the pulse. As the substrate bias increases from −17.3 V (floating voltage) to −100 V, the electron current gradually decreases, while the ion current increases, eventually stabilizing at −50 V. However, the changes in the deposition rate, tensile stress and texture of Cu films deposited from floating voltage to −50 V showed little difference as opposed to those Cu films deposited in the range from −50 V to −100 V. Compared to the Cu films deposited at −50 V, the films deposited at −100 V exhibited a higher tensile stress and a superior (111) texture. The electrical resistivity of the Cu films reached a minimum value of 1.79 μΩ cm at −100 V.