In situ study on low-k interconnect time-dependent-dielectric-breakdown mechanisms

Abstract

An in situ transmission-electron-microscopy methodology is developed to observe time-dependent dielectric breakdown (TDDB) in an advanced Cu/ultra-low-k interconnect stack. A test structure, namely a “tip-to-tip” structure, was designed to localize the TDDB degradation in small dielectrics regions. A constant voltage is applied at 25 °C to the “tip-to-tip” structure, while structural changes are observed at nanoscale. Cu nanoparticle formation, agglomeration, and migration processes are observed after dielectric breakdown. The Cu nanoparticles are positively charged, since they move in opposite direction to the electron flow. Measurements of ionic current, using the Triangular-Voltage-Stress method, suggest that Cu migration is not possible before dielectric breakdown, unless the Cu/ultra-low-k interconnect stacks are heated to 200 °C and above.

Measurements of Schottky barrier at the low-k SiOC:H/Cu interface using vacuum ultraviolet photoemission spectroscopy

“…11 Electron transport across the low-k cappinglayer dielectric and the Cu-line interface, however, represents another possible leakage path for low-k/Cu interconnects, which brings a serious reliability challenge. 15 To fully explore the possibilities of line-line and/or layer-layer leakage, one must therefore also examine the band alignment between Cu and low-k a-SiOC:H dielectrics used both as interlayer and Cu capping-layer dielectrics. To address this issue, this work utilizes vacuum ultraviolet (VUV) photoemission spectroscopy to measure the Schottky-barrier potential at low-k a-SiOC:H/Cu interfaces.…”