Sulfate Radical Oxidation for Enhancing Polishing-Rate Forhardmask-Film Chemical–Mechanical-Planarization

Recently, to scale down semiconductor devices less than several nm (i.e.,m 5, 4, and 3 nm), lithography using a 193 nm ArF excimer laser, extreme ultraviolet lithography (EUVL), and 13.8 nm laser-produced plasma were applied. However, since photoresist patterns with a high aspect ratio could easily result in collapse of photoresist patterns, a carbon polymer hardmask between the photoresist and the substrate film has been introduced. The carbon polymer hardmask produces a high surface topography induced by pattern density, requiring chemical-mechanical planarization (CMP) for removing such surface topography. Although, the demand for hardmask-film CMP slurries performing high polishing-rate has been increased, the improving the carbon polymer hardmask-film polishing-rate has been considered difficult because of its hardenss caused by C-C sp 3 and C-C sp 2 covalant bonds. In this study, as a solution, unlike conventional oxidizing agent such as hydrogen peroxide(H 2 O 2 ), sulfate radical oxidant (i.e., Patassium persulfate) was used in the hardmask-film CMP slurry for acheiving high quality surface roughness and enhancing hardmask-film polishing-rate. The new designed CMP slurry evidently accomplished hardmask surface oxidation via transformation from C-C sp 3 and C-C sp 2 covalent bonds to C-O bond during CMP, resulting an extremely high polishing-rate (i.e., 300 Å/min) and high quality surface roughness (i.e., 0.36 nm at 5x5 um 2 ) at the sulfate radical oxidant concentration of 1 wt%. In our presentation, we will prove the mechanism of the sulfate radical oxidation on the polished hardmask-film surface. In addition, we will present the dependencies of the chemical dominant polishing properties (i.e., OH radical, chemical oxidation degree of the Ag-film surfcae, chemical composition of chemical oxidation, and slurry adsortion degree) as well as the mechanical dominant polishing properties (i.e., electrostatic force between abrasives and hardmask-film surface) on the surfate oxidant concentration. Acknowledgment This research was supported by the MOTIE(Ministry of Trade, Industry & Energy (1415180388) and KSRC(Korea Semiconductor Research Consortium) (20019474) support program for the development of the future semiconductor device, and by the Brain Korea 21 PLUS Program and the Samsung Display Co. Ltd. Figure 1