Published online by Cambridge University Press: 01 February 2011
The AC fatigue test technique, which uses cyclic joule heating to apply thermal cycles to thin-film structures, was applied to copper lines and vias in damascene dielectric structures on silicon substrates. Specimen chips with two different types of dielectric, oxide and low-k, were tested. The lines were 300 nm wide; various via widths were tested. At 100 Hz, cyclic temperature ranges from 400 to 900 °C produced line lifetimes between 10 and 1 million seconds. Similar lifetimes were reached in the vias for temperature ranges between 100 and 500 °C. The data were plotted as number of load reversals to failure against cyclic temperature range; the data trends for the two different types of dielectric were indistinguishable. When the line data were fit to the Basquin equation for mechanical fatigue, the temperature ranges for both dielectrics at the one1-reversal intercept were above 1000 °C. The via data were more scattered, but trended toward a lower intercept temperature.