Development of a novel wet cleaning solution for Post-CMP SiO2 and Si3N4 films

Abstract

After CMP, the removal of ceria nanoparticle residues is difficult due to the formation of Ce–O–Si chemical bonds on the SiO2 film surface. After STI CMP, several post-CMP cleaning processes are performed, including the application of PVA brushing and megasonic technologies using conventional cleaning solutions such as SC1, SC2, and SPM. However, more effective post-CMP cleaning technologies are still needed for the fabrication of advanced integrated circuit devices. In this study, we developed a novel post-CMP cleaning solution consisting of tetramethylammonium hydroxide (TMAH), ethylenediaminetetraacetic acid (EDTA), and Disponil to replace existing cleaning solutions. In its non-diluted form, this cleaning solution removed 99.5% of residual particles and 98.3% of ceria residue on an SiO2 film surface, as well as 98.5% of residual particles and 98.1% of ceria residue on an Si3N4 film surface, respectively. At 5 × dilution, it removed 97.8% of residual particles and 97.0% of ceria residue on the SiO2 film surface, as well as 97.8% of residual particles and 96.3% of ceria residue on the Si3N4 film surface, respectively. The effectiveness of this cleaning solution for residual ceria nanoparticles is highly comparable to SC1 and SPM conventional cleaning solutions, even though it is used at a relatively low temperature with less etching. Additionally, AFM of the surface topography showed fewer particles and better surface roughness compared with SC1 and SPM cleaning. Thus, this approach can be used to remove ceria nanoparticles from polished SiO2 and Si3N4 films through increased wettability, slight dissolving of the film, and extremely enhanced repulsive force.