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 biastemperature stress. At a field of 1.0 MV/cm and temperature of 100 °C, Cu ions drift readily into PECVD oxide with a projected accumulation of 2.7×10¹³ ions/cm² after 10 years. However, in PECVD oxynitride, the projected accumulation under the same condition is only 2.3×10¹⁰ ions/cm². 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.