Electromigration Testing of Al-Alloy Films

Abstract

A search for reliability improvement of Al film interconnections has led to the introduction of Al-Alloy films such as Al+Cu, Al+Si, Al+Cu+Si and so on. This paper describes thie results of an in-depth study of Al, Al+Cu (2 wt % Cu) and Al+Cu+Si (2 wt % Cu + 1 wt % Si) film interconnections and Silicon/Al-Alloy film contacts as they impact reliability of integrated circuits. Resistivity, microstructure and composition of Al-Alloy films vacuum deposited from an induction heated source (In-Source) and dc magnetron sputter deposition techniques have been investigated and it is concluded that both film deposition techniques are equally capable of producing these Al, Al+Cu (2 wt % Cu) and Al+Cu+Si (2 wt % Cu + 1 wt % Si) films of comparable physical properties. Chemical Analysis, X-Ray Fluorescence, Electron Microprobe, Scanning and Transmission Electron Microscopy and Ion Microprobe have been employed for Al-Alloy film characterization. Availability of automated dc magnetron sputter deposition equipment was a primary factor in the selection of magnetron sputter deposited Al-Alloy films for electromigration testing. Electromigration life tests on Al, Al+Cu and Al+Cu+Si film conductors (0.8 ¿m thick, 6 ¿m wide and 380, ¿m long) have been carried out at a current density of 1 × 106/ A/cm2 in the 150°C to 215°C ambience. Also, shallow junction devices with depths on the order of 0.