In-Source Ai-0.5%Cu Metallization for CMOS Devices

This study examines the use of radiation-free RF induction-source evaporated (In-Source®) Al-0.5%Cu as a viable metallization scheme for CMOS devices. The fact that it is radiation free offers ways of optimizing the thermal cycle so as to achieve desirable device and electromigration characteristics. Wafers fabricated with 3.5 μm design rules have shown no threshold shifts or changes in the transistor gain at sintering temperatures up to 450°C, in either H₂or N₂, for both N and P-channel devices, confirming the absence of deposition-induced fixed interface charges. Wafers processed with 2.5 μm design rules have exhibited low and well-behaved values of contact resistance to N⁺and P⁺diffusions, at sintering temperatures in the range 300°-400°C in either H₂or N₂, with no evidence of junction penetration. Electromigration measurements, gathered over a wide range of processing conditions, have yielded values of median time to failure (MTF) that were observed to improve with narrower linewidths, higher sintering temperatures, and in the presence of a plasma SiN passivation coating. In typical device operation conditions of 80°C and 1Χ10⁵A/cm², the extrapolated MTF value of 3.6Χ10⁷h, for 3.0 μm wide In-Source Al-0.5% Cu lines is found to exceed the value of ~2Χ10⁶h reported for E-Gun Al-0.5% Cu.