The dependence of stress induced voiding on line width studied by conventional and high resolution resistance measurements

Abstract

The degradation due to stress induced voiding of nitride passivated Al-1 wt.% Si and Ti/TiN/Al-1wt.% Si-0.5 wt.% Cu/Ti/TiN interconnects with widths ranging between 0.4 and 1.2 mu m was studied by insitu conventional and high resolution resistance measurements (HRRM) during storage at temperatures between 168 and 240 degrees C. The conventional measurements on Al-Si lines, which lasted more than one year, clearly showed that the interconnect lifetime decreases with decreasing line width. With HRRM the degradation due to stress induced voiding can be detected much sooner and with much more detail. From the HRRM it is clear that the resistance changes during storage often happen in jumps and that the degradation has a rather complex alloy, line width and temperature dependence. Both for 0.4 and 0.6 mu m wide AI-Si lines more degradation occurred fix storage at 175 degrees C compared to storage at 200 degrees C. For the Al-Si-Cu stacks the degradation of 0.4 mu m wide lines was worse for storage at 240 degrees C compared to storage at 200 degrees C, but the opposite was true for the 0.6 mu m wide lines. (C) 1998 Elsevier Science Ltd. All rights reserved.