Comprehensive study of corrosion mechanisms in Integrated Circuit (IC) copper metal lines within TEM lamellae

Corrosion of copper circuitry features embedded in a Transmission Electron Microscope (TEM) lamella prepared from semiconductor devices can be a significant issue for process monitoring, as it can cause the observed patterns to be either masked or distorted, and also as it may modify the structure and composition of samples. Impacted TEM lamellae have been tracked for several months, with no correlation from sample preparation equipments nor human behavior. To understand corrosion mechanisms, in-depth studies were performed to evidence elements responsible for copper segregation using Energy-Dispersive X-Ray Spectroscopy (EDS) or Electron Energy Loss spectroscopy (EELS), revealing the presence of chlorine, sulfur and oxygen elements. Specific tracking of air composition of the laboratory indicated no excess of contaminant species. The use of protective coatings and structure grounding during Focused Ion Beam (FIB) preparation of the TEM lamella have been tested and revealed to be efficient to eradicate corrosion.