A new abrasive-free planarization method for silicon carbide (SiC) wafers was proposed using the catalytic nature of platinum (Pt). We named it catalystreferred etching (CARE). The setup equipped with a polishing pad made of Pt is almost the same as the lapping setup. However, CARE chemically removes SiC with an etching agent activated by a catalyst in contrast to mechanical removal by the lapping process. Hydrofluoric acid which is well known as an etchant of silicon dioxide (SiO 2 ) that cannot etch SiC, was used as the source of the etching agent to SiC. The processed surfaces were observed by Nomarski differential interference contrast (NDIC) microscopy, atomic force microscopy (AFM), and optical interferometry. Those observations presented a marked reduction in surface roughness. Moreover, low-energy electron diffraction (LEED) images showed that a crystallographically well-ordered surface was realized.

The authors present a method for flattening SiC surfaces with Pt as a catalyst in HF solution. The mechanism for flattening SiC surfaces is discussed. The flattened 4H-SiC(0001) surface is composed of alternating wide and narrow terraces with single-bilayer-height steps, which are induced by the rate difference of the catalytic reactions between adjacent terraces. Scanning tunneling microscopy images reveal a 1×1 phase on the terraces. The 1×1 phase is composed of coexisting of F- and OH-terminated Si atoms, which originate from the polarization of the underlying Si–C bonds.

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A method for preparing atomically smooth gallium nitride (GaN) surfaces that involves chemical etching with a platinum catalyst in water is presented. The flattened GaN(0001) surface exhibits periodic structures composed of straight-edged steps the height of a single bilayer. Atomic step and terrace structures containing an extremely small number of scratches and pits can be achieved on wafer scale (2 inch diameter). Photoluminescence analysis revealed that the intensity of band-edge luminescence increases significantly after flattening. Low energy electron diffraction indicated that the flattened GaN surface is crystallographically well-ordered. Current density between the wafer and Pt is observed when they are rotated, suggesting that the GaN surface is etched by an electrochemical reaction initiated by the tribo effect between Pt and the wafer surface.

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