Silicon-Germanium on Insulator CMP Slurry Designed with Oxidant and Accelerator Heading an Amine Functional Group for Remarkably Enhancing Polishing Rate

Abstract

High quality single crystal silicon-germanium-on-insulator (SGOI) has a potential to enable the next generationof photonic and electronic devices. However, to utilize an SGOI structure, a high SiGe-film polishing rate isnecessary (i.e., > 200 nm/min) for polishing the facet crystalline SiGe during the fabrication of SiGe on insulatorthrough epitaxial growth processes.In previous studies, amine-based chemicals as SiGe-film polishing rate accelerators have been reported, butthere were limitations in increasing the SiGe-film polishig rate by considering only the chemical reaction of SiGe-film surface. In this study, for the first time, both oxidant(i.e., H2O2) and accelerator with amine functional groups(i.e., triethanolamine) were designed, resulting in a surprising increase in the SiGe-film polishing rate of 270nm/min, as shown Fig. 1a.The SiGe chemical mechanical planarization (CMP) mechanism was clearly demonstrated by preciselyinvestigating both chemical properties(i.e., GeO2 spectra intensity via X-ray photoelectron spectroscopy) andmechanical properties(i.e., electrostatic repulsive force between colloidal silica abrasives and the SiGe-film viaelectrophoretic light scattering). The remarkable enhancement of the SiGe-film polishing rate for oxidant andtriethanolamine was the result of (i) minimizing the loss of degree of SiGe surface oxidation, as shown Fig. 2, (ii)enhancing degree of adsorption of the CMP slurry on the polished SiGe-film surface during CMP, and (iii)decreasing the electrostatic repulsive force between colloidal silica abrasives and the SiGe-film surface, as shownFig 1b. Finally, successful removal of the facets in SiGe on insulator wafers was achieved, securing excellentsurface roughness characteristics. SiGe-film polishing mechanism and the SiGe slurry characteristics will bepresented in detail. Figure 1