Chemical mechanical planarization of copper thin films

Chemical mechanical planarization (CMP) has become the process of choice for surface global planarization for copper damascene interconnect processing and other metal surfaces such as Ta, TaN, W, Ti, TiN and SiO2 in the fabrication of advanced multilevel integrated circuits (IC) in microelectronic industry. Cu CMP has become an essential step in today's advanced semiconductor devices fabrication process. In addition to abrasive particles, complexing agent, and oxidizer, a key additive in copper CMP slurry is the so-called passivating agent. The main function of the passivating agent is to protect the copper film from aggressive chemical attack that may lead to isotropic dissolution of the copper film. With the protection of such passivating agent, only the copper film in the protruded area is selectively removed by mechanical force thus yield a step height reduction. As a strong corrosion inhibitor, benzotriazole (BTA) is the most commonly used passivating agent in copper CMP slurry. BTA's passivating ability is significantly reduced at a lower pH due to protonation, especially at pH below 5. At high pH, BTA is known to introduce defects such as scratch and delamination. Therefore there is a need for finding a good passivating agent that forms a protective and stable film on the copper surface which can withstand chemical action of the slurry. This work aims at investigating such new inhibiting agents for copper CMP slurries and the role of those agents in copper CMP process.; Tetrazole compounds such as 5-aminotetrazole (ATA), 5-Phenyl-IH-tetrazole (PTA), 1-Phenyl-1H-Tetrazole-5 thiol (PTT), as corrosion inhibitors in hydrogen peroxide based slurries were investigated. Copper static etch rate and material removal rate experiments at different slurry chemical compositions and at different pH were performed.; Experiments were conducted with slurry/solution containing silica abrasive particles and no abrasive particles. The results show that tetrazole compound offers good surface passivation for copper in CMP process. Electrochemical measurements were performed with CMP slurry containing tetrazole compounds. Potentodynamic polarization studies were used to examine the passivation behavior of inhibitor in static CMP slurry. In the presence of inhibitors the cathodic and anodic curves were shifted to the higher potential region. Shift of cathodic and anodic polarization curves is an indication that the inhibiting agent forms a protective film on the copper surface. (Abstract shortened by UMI.)...