Controlling Diameter and Morphology of Colloidal-Silica-Abrasives Via Designing Surfactant Functional Group

Abstract

As the design rule of logic semiconductor has been scaled down toward 5, 3, 2.1, 1.5, and 1.0 nm, the line width of Cu-film as interconnect line of logic semiconductor has been rapidly scaled down toward 36, 32, 24, 20 and 16 nm. The CMP of the Cu-lines is essential fabrication process, challenging an achievement of dishing and erosion during Cu-film CMP. In particular, the dishing and erosion of the Cu-film CMP has been principally affected by the diameter and morphology of colloidal-silica-abrasives in a CMP slurry. In a conventional synthesis method synthesis of colloidal-silica-abrasives, ethoxysilanol was formed via the hydrolysis reaction by Tetraethyl orthosilicate(TEOS) and H2O producing ethoxysilanol, following the condensation reaction between two ethoxysilanol. The diameter of colloidal-silica-abrasives could be obtained by adjusting the concentrations of TEOS, alcohol, and alkali catalyst, but the solid loading of colloidal-silica-abrasives could be varied. Thus, in our study, a novel synthesis method of the colloidal-silica-abrasives was designed by adding a charged functional group surfactant during the conventional colloidal-silica-abrasives synthesis method. The effect of the surfactant having negative charged carboxyl functional group (i.e. Ethylenediaminetetraacetic acid: EDTA) on the diameter and morphology of the colloidal-silica-abrasives were investigated as function of the EDTA concentration; i.e. when the concentration of EDTA increased from 0 to 0.03 wt%, the diameter of colloidal-silica-abrasives increased from 47.0 to 103.8 nm and the solid loading of colloidal-silica-abrasives increased from 2.0 to 2.36 wt%, as shown in Fig. 1. In addition, when the ETDA concentration increased above 0.0025 wt%, the morphology of colloidal-silica-abrasives was transformed from cocoon shape to spherical shape. Furthermore, the effect of the surfactant having the positive charged amine functional group (i.e. Triethanolamine: Tri-ETA, Ethylenediamine: EDA, Diethylenetriamine: DETA, Triethylenetetramine: TETA) were estimated as function of the number of amine functional group in the surfactant, as shown in Fig. 2. When the number of positive charged amine functional groups increased 0 to 4, the diameter of colloidal-silica-abrasives increased from 67.2 to 143.86 nm and the solid loading of colloidal-silica-abrasives increased from 2.0 to 2.2 wt%. In addition, the synthesis with positive charged amine functional group was transformed from cocoon shape to spherical shape. The synthesis mechanism, the enhanced polishing rate of Cu-film surface, dishing and erosion after Cu-film will be presented in detail. Acknowledgement 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. Figure 1