A multilevel interconnect technology with intrametal air gap for high-performance 0.25-mu m-and-beyond devices manufacturing

A multilevel interconnect technology with an intra metal air gap has been d eveloped to reduce the interconnect delay time for versatile. and quick tur naround-time foundry manufacturing. The air-gap method has been successfull y applied to 0.25 mu m IC technology and shown to be effective in reducing the parasitic interconnect capacitance. Measurements of various ring oscill ators confirm that the smallest delay time is indeed achieved with the air- gap method, compared with other methods using either conventional high-dens ity-plasma (HDP) oxide or low-dielectric-constant spin-on-glass (SOG) as th e gap-filling insulating materials. Moreover, the oscillator delay time is found to depend critically on not only the size of the air gap, but also th e position of the air gap. Best results in terms of delay time reduction ar e obtained when the air-gap is positioned in the middle between the two met al lines, and extends both above and below the metal lines to effectively r educe the fringing capacitance. We have also measured the leakage current b etween adjacent metal lines and confirmed that our new metal intel connect structure with an air gap does not exhibit any appreciable leakage and appe ars to be suitable For high-performance foundry applications. Lastly, the p olarization and thermal characteristics of the air-gap structure were compa red with conventional gap-filling methods.