Reliability of polymide/nitrate dielectrics for multilevel metallization systems

A comparison of combinations of polymide (PIQ-13) and Si/sub 3/N/sub 4/ dielectric layers is presented concerning their resistance against moisture uptake. Conventional oxide dielectrics are taken as a standard. A pressure-cooker test shows that a passivating Si/sub 3/N/sub 4/ layer on top of every polyimide layer results in a dielectric system whose reliability is comparable to conventional oxide dielectrics. Extremely low leakage currents of around 1 pA occur after the pressure-cooker test have been achieved and characterize the high level of reliability. It is concluded that a Si/sub 3/N/sub 4/ interlayer acts as a reliable adhesion layer to subsequent metal layers, and that it is necessary as an etch stop for subsequent metal etch processes in VLSI technology.<>