Electro-Chemical Mechanical Polishing of 4H-SiC for Scratch-Free Surfaces with Less Oxide Layer at High Efficiency

Abstract

4H-SiC has been widely exploited in semiconductor industry. Nevertheless, the scratch-free surface with less oxide layer (required for its high-performance) is difficult to realize at high efficiency. Hence, to address this issue, an electrochemical mechanical polishing (ECMP) test was conducted based on the electrochemical-mechanical balance between the SiC corrosion rate and the SiO2 layer removal rate. Firstly, we synthesized polystyrene (PS)/CeO2 core/shell abrasives, which have the potential to obtain the high-quality surface due to its elastic effect. These as-synthesized abrasives were then characterized by FESEM and XRD. Results showed the CeO2 shells were coated on the PS cores successfully. Next, equations of the SiO2 layer removal rate and the SiC corrosion rate were experimentally obtained based on the modified Preston's equation and the Faraday's law of electrolysis, respectively. Finally, a verified test for 4H-SiC-ECMP was conducted in a 0.2 M NaOH electrolyte solution containing 5.0 wt% PS/CeO2 abrasives. After ECMP, these samples were characterized by microscope, AFM, Raman spectrometer and profile-meter, respectively; and the scratch-reduction mechanisms were deduced based on these characterization results. Results showed under balanced conditions, the scratch-free surface (Ra: 0.449 nm) with less oxide layer was obtained at high efficiency (∼2.3 μm/h).