Manufacturing Process Of Ultra-deep Sub-micron Aluminum Interconnect Electromigration Reliability

The reliabilities of semiconductor chips are important topics for academy and industry, and electromigration (EM) failure is the most important and persistent challenge among them. As the most advanced Al interconnect technology, unlra-deep submicron (0.18-0.15μm) Al interconnect is currently not only the dominant IC fabrication technology but also faces successional new EM issues. So studying the process effects on Al EM problems will help to better understand EM phenomena and provide solutions for industry. Also, it is beneficial to the technical advancement of semiconductor industry in China.This dissertation systematically studied the fabrication process effects on electromigration in ultra deep submicron Al interconnects. Firstly, it summarized the existing theories and deduced the atomic flux equation, which correlates the important physical parameters to EM lifetime. For the fact that physical parameters determined by manufacturing processes, the dissertation then discussed the characters of ultra-deep submicron Al interconnect technology and concluded that important factors - including microstructures,temperature and current distributions,interface properties - dominate the EM reliability of ultra-deep submicron Al interconnects.In the experimental part, the dissertation presented the mechanisms of how important process steps, especially thin film deposition, affect film microstructures, current crowding phenomena and interface reactions. Firstly, the effects of three typical Ti underlayers -standard Ti,pure Ti and ionized-metal-plasma (IMP) Ti - on film microstructures and EM performance were studied. The strong correlation among surface roughness,reflectivity,texture and EM lifetime was discovered and well explained. What's more, the effects of substrate bias in IMP process were further studied and lower bias was found better for microstructures. For current crowding effects, a model combining EM lifetime and current density distribution was proposed. It was also proved by simulation and experimental results. For interface effects, the study focused on the reaction between underlayer TiN and AlCu films as well as its effects on wafer level and package level EM results.Finally, all the achievements and innovations of the dissertation were summarized.