Controlling Germanium CMP Selectivity through Slurry Mediation by Surface Active Agents

New developments and device performance requirements in microelectronics industry add to the challenges in chemical mechanical planarization (CMP) process. One of the recently introduced materials to semiconductor manufacturing is germanium which enables improved device performance through better channel mobility in shallow trench isolation (STI) applications for advanced circuits. This paper focuses on controlling germanium/silica selectivity for advanced STI CMP applications through slurry modification by surface active agents. Surface adsorption characteristics of cationic and anionic surfactants on germanium and silica wafers are analyzed in order to control selectivity as well as the defectivity performance of the CMP applications. The effects of surfactant charge and concentration (up to self-assembly) are studied in terms of slurry stability, material removal rates and surface defectivity. Surface charge manipulation by the surfactant adsorption on the germanium surface is presented as the main criteria on the selection of the proper surfactant/oxidizer systems for CMP. The outlined correlations are systematically presented to highlight slurry modification criteria for the desired selectivity results. Consequently, the paper evaluates the slurry selectivity control and improvement criteria for the new materials introduced to microelectronics applications with CMP requirement by evaluating the germanium silica system as a model application.