In-situ study of the TDDB-induced damage mechanism in Cu/ultra-low-k interconnect structures

<em>In Situ</em> Time-dependent Dielectric Breakdown in the Transmission Electron Microscope: A Possibility to Understand the Failure Mechanism in Microelectronic Devices

“…Nevertheless, the TDDB damage mechanism observed is believed to be valid because: (1) with much less TEM beam irradiation (low-dose STEM imaging, low illumination step and recording images every 30 min/1 h), the test sample showed similar failure mechanisms as in our previous TEM observation (recording images continuously, relatively high-dose TEM mode) [16][17][18] ; (2) the electrical field was confirmed as the driving force and the origin of the migration of metal particles 17 ( Figure 5B and 6A) by reversing the electrical connection; (3) migration of metal particles and dielectric breakdown were both observed at specific locations where the tip-to-tip spacing is relatively small and the Ta/TaN barrier is relatively thin, not everywhere inside the illumination area of the TEM beam; (4) a thick layer of Pt deposition on top of the sample prevents most of the contamination from the vertical implantation of Ga ions -the test structure is believed to be mainly contamination free even if there is a slight amount of contamination on the surface of the side walls (about 60 nm) from the lateral damage of the Ga ions. Therefore, the sample preparation and the TEM observation should not affect the interpretation of the intrinsic failure mechanism to a significant amount.…”

“…The TEM image after breakdown is shown in Figure 5B. Apparently, metal atoms migrated into the SiO 2 from the bottom corner of the M1 metal, having a positive potential indicated by a red arrow 17 . The ESI chemical analysis ( Figure 5C) proves that there is a migration path of Cu at the fracture interface between the SiCN layer and the ULK dielectrics, which could not be detected from the contrast of the BF TEM image in Figure 5B.…”