Abstract
For effective machining of difficult-to-machine materials, such as reaction-sintered silicon carbide (RS-SiC) and single-crystal 4H silicon carbide (4H-SiC), a novel polishing technique named anodic oxidation polishing was proposed, which combined with the anodic oxidation of substrate and slurry polishing of oxide. By scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM-EDX) observation and atomic force microscopy analysis, both the anodic oxidation behaviors of RS-SiC and 4H-SiC were investigated. Through comparison of the surfaces before and after hydrofluoric acid etching of the oxidized samples by the scanning white light interferometry (SWLI) measurement, the relationships between oxidation depth and oxidation time were obtained, and the calculated oxidation rate for RS-SiC was 5.3 nm/s and that for 4H-SiC was 5.8 nm/s based on the linear Deal–Grove model. Through anodic oxidation polishing of RS-SiC substrate and 4H-SiC substrate, respectively, the surface roughness rms obtained by SWLI was improved to 2.103 nm for RS-SiC and to 0.892 nm for 4H-SiC. Experimental results indicate that anodic oxidation polishing is an effective method for the machining of RS-SiC and 4H-SiC samples, which would improve the process level of SiC substrates and promote the application of SiC products in the fields of optics, ceramics, semiconductors, electronics, and so on.
Highlights
Silicon carbide (SiC) is a promising material for semiconductors, ceramics, and optics [1, 2], since it has remarkable excellent mechanical and chemical properties [3, 4]
For effective machining of difficult-to-machine materials, such as reaction-sintered silicon carbide (RSSiC) and single-crystal 4H silicon carbide (4H-SiC), a novel polishing technique named anodic oxidation polishing was proposed, which combined with the anodic oxidation of substrate and slurry polishing of oxide
Through comparison of the surfaces before and after hydrofluoric acid etching of the oxidized samples by the scanning white light interferometry (SWLI) measurement, the relationships between oxidation depth and oxidation time were obtained, and the calculated oxidation rate for reaction-sintered silicon carbide (RS-SiC) was 5.3 nm/s and that for 4H-SiC was 5.8 nm/s based on the linear Deal– Grove model
Summary
Silicon carbide (SiC) is a promising material for semiconductors, ceramics, and optics [1, 2], since it has remarkable excellent mechanical and chemical properties [3, 4]. Ultrasmooth 4H-SiC surface can be obtained in chemical mechanical polishing (CMP) [9], plasma-assisted polishing (PAP) [10], and CAtalyst-Referred Etching (CARE) [11], the material removal rates (MRR) in these techniques are low. As the composition and structure of RS-SiC are not uniform [12], few of the techniques which have been developed to process RS-SiC substrates can yield smooth surface and obtain high material removal rate simultaneously [13]. Anodic oxidation has been developed for the oxidation of silicon, and we applied it to process SiC [14]. By calculation of oxidation rate based on the Deal–Grove model [15] and comparison of surface quality, the superiority of anodic oxidation polishing of SiC substrates was revealed
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