In order to evaluate the potential of a non-plasma dry etcher for silicon carbide, a 50-mm-diameter C-face 4H-silicon carbide wafer was etched using chlorine trifluoride gas at 500 • C. The wafer deformation was sufficiently small after the repetitive etching, even though the wafer was very thin, that is, about 160-μm thick. When the wafer surface was significantly etched, concentric-circleshaped valleys were formed at the radii corresponding to the circular-shaped arrays of pinholes at the gas distributor. Because the local pattern of the 4H-silicon carbide wafer etching rate corresponded to that of the chlorine trifluoride gas supply, the etching rate distribution was determined to be mainly governed by the chlorine trifluoride gas flow. Because the surface morphology and roughness after the etching was comparable to that of the mirror-polished wafer surface, the etcher evaluated in this study was expected to have a significant potential for mirror etching. In order to reduce the electric energy loss, power electronics 1-3 is currently playing major roles and making enormous contributions over the world. The power devices have various key positions to govern and improve the overall power consumption efficiency. They will have more functions and capabilities achieved by advancing the technologies of material production and device designs.The power devices are made of semiconductor materials, 2,3 such as silicon (Si), silicon carbide (SiC) and gallium nitride (GaN). The silicon carbide power devices have been developed by many researchers and engineers due to their fascinating nature, such as a high dielectric breakdown voltage, for high voltage use. The silicon carbide power devices are actually installed and currently working in trains and vehicles.2,3 Because the power device demand will further increase in the future, the process of silicon carbide material production should be improved.The significantly hard and nonreactive properties of the silicon carbide very often make the device fabrication processes long and complex. When the wafer back side is thinned by mechanical or chemical mechanical polishing after the device fabrication, the thinning processes require several hours or more. The removal rate is still about 0.2 μm/min when the plasma and Pt catalyst are used for the polishing.4-10 For developing a high speed process, an alternative high speed process, such as chemical etching, is expected.For improving the removal rate by the chemical approach, chlorine trifluoride (ClF 3 ) gas 11-17 is expected to be useful. The chlorine trifluoride gas has been reported to quickly etch the Si-and C-faces single-crystalline 4H-silicon carbide (SiC) material at a high rate, such as 5 μm/min.11 The C-face 4H-silicon carbide could be etched while maintaining the mirror-polished surface. 11,17In order to realize an industrial-scale wafer etching process, the SiC single-wafer dry etcher has been designed, fabricated and evaluated. [13][14][15][16] In this reactor, the entire etching rate profile over the 50 mm-diamet...

The etching rate profile over the 50-mm diameter single-crystalline C-face 4H-SiC wafer by ClF3 gas was numerically evaluated by means of the numerical calculation accounting for the transport phenomena. The etching rate uniformity is expected to be improved by means of adjusting the pinhole diameter and their arrangement of the gas distributor.

In order to effectively and quickly clean the surface of semiconductor silicon wafers, the fluid flow is one of the significant issues. For a batch-type silicon wafer wet cleaning bath, a slim water injection nozzle consisting of a dual tube was studied, based on theoretical calculations and experiments. A thin inner tube was placed at the optimum position in the water injection nozzle. Such a simple design could make the water injection direction normal and the water velocity profile symmetrical along the nozzle. The water flow in the wet cleaning bath was observed using a bluecolored ink tracer. When the nozzle developed in this study was placed at the bottom of the bath, a fast and symmetrical upward water stream was formed between and around the wafers.

A method to adjust the polycrystalline SiC etching rate was studied taking into account the chlorine trifluoride gas transport. The etching rate profile over the 50-mm-diameter SiC wafer could be made symmetrical by means of the wafer rotation. By activating and indeactivating the pin-holes at the various positions of the gas distributor, the etching rate profile could be locally adjusted.

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