Kinetics of copper drift in PECVD dielectrics

We quantified the drift of Cu ions into various PECVD dielectrics by measuring shifts in capacitance-voltage behavior after subjecting Cu-gate MOS capacitors to bias-temperature stress, At a field of 1.0 MV/cm and temperature of 100 degrees C, Cu ions drift readily into PECVD oxide with a projected accumulation of 2.7 x 10(13) ions/cm(2) after 10 years, However, in PECVD oxynitride, the projected accumulation under the same conditions is only 2.3 x 10(10) ions/cm(2). These findings demonstrate the necessity of integrating drift barriers, such as PECVD oxynitride layers, in Cu interconnection systems to ensure threshold stability of parasitic field n-MOS devices.