Investigation of Effect of L-Aspartic Acid and H2O2 for Cobalt Chemical Mechanical Polishing

Abstract

Cobalt, the 3rd generation material for interconnect in deep nanometers’ processing. Cobalt reduces the interconnect structure and process complexity compared to the dual damascene process. In this article, we investigate the effects of complexing agent L-Aspartic acid (L-Asp) and oxidant H2O2 for polishing Cobalt based on chemical mechanical polishing (CMP). The results show that the water-soluble Co(III)-L-Asp complex generated by adding L-Asp and H2O2 is beneficial to improve the Cobalt removal rate. Electrochemical measurements and X-ray photoelectron spectroscopy are ultilizd to explore the removal mechanism of Cobalt. The high removal rate of Cobalt may be attributed to the formation of [Co(C4H5NO4)2−] and [Co(C4H5NO4)22−] complexes. The surface morphology of cobalt is observed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The results show that obvious corrosion phenomenon appears on the surface of cobalt after adding H2O2 and L-Asp, which also confirms the chemical reaction mechanism in which the removal rate is improved as previously analyzed.